How to Diagnose a Flashing Check Engine Light?

So now, that we know what could cause this, where should we begin to pinpoint the problem?

You must understand that every time your check engine light is constantly lightened up or blinking, it will store a trouble code in the memory so you will have a chance to see what was causing the problem.

Therefore it is a terrible practice just to guess which parts could cause the check engine light and start to replace parts. This will, in almost all cases, just make you waste your money.

A much better and more efficient method is to check what the engine control unit is trying to tell us. This can be done with a diagnostic scanner.

You may think that a diagnostic scanner is too expensive for this small problem, and in that case, you can borrow one from a friend or just take your car to a repair shop and let them read the codes for you.

After you have received the engine control unit’s codes, you will most likely find a trouble code related to a misfire. Check for more related trouble codes to continue the troubleshooting on that trouble code.

For example, if you get a misfire trouble code and one related to an ignition coil, you should definitely continue troubleshooting that ignition coil.

If you get misfires on a specific cylinder – check the spark plugs, ignition coils, and wirings. If you get misfires on several cylinders, there is most likely an issue with a too lean or too rich mixture.

Conclusion: Flashing Check Engine Light

A flashing warning light indicates that there is a serious problem with your car’s engine and is usually caused by engine misfires. If left unaddressed, this problem can lead to very expensive repairs.

While it can be tempting to ignore a flashing check engine light if the engine is running fine, it’s still very important to either diagnose it yourself or take your car to a mechanic as soon as possible.

If you see a flashing engine light, but feel that you do not have the knowledge to diagnose the car yourself, do not hesitate to take your car in for diagnosis and repair by a professional.

How to Perform a Basic Drive Cycle

a drive cycle is one of the methods used by a vehicle's powertrain control module (pcm) to determine whether an emissions system repair was performed successfully. it involves a special test drive that duplicates the scenario of a person starting the car and making a short freeway trip, as if driving to work. while the drive cycle test is going, the engine computer runs a series of tests or "readiness monitors" to see if the emissions system is working properly.

what is the purpose of a drive cycle?

when a vehicle has an emissions system problem, it almost always triggers a check engine or service engine soon light. this signals that an emission system problem and fault code has been recorded in the powertrain control module (pcm). the problem indicated by the fault code must now be accurately diagnosed and repaired.

after the proper repair has been completed and the fault code cleared, the pcm will run a series of self-tests to determine whether or not the repair actually corrected the problem and if the various emissions systems are running properly. if they are, they can now properly minimize the emissions released into the atmosphere from the vehicle's operation.

this process was designed to prevent a vehicle from slipping through an emissions test with a known problem. until 1996, a common tactic was to turn off the check engine light by clearing the code just before an emissions test, without performing the proper repair. the drive cycle and emissions readiness monitors have, for the most part, stopped this unethical tactic.

get professional help

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how to perform a basic drive cycle

here are step-by-step instructions on how to perform a basic, yet very effective, drive cycle that will complete the readiness monitors for your vehicle's emissions control system.

step one: how to prepare your vehicle

• have the fuel tank between 30 and 70 percent full. some systems, especially the evap system, need to have a specific level of fuel in order for the tests to be trusted. if the fuel tank is near empty or completely full, many of the basic tests will not run at all.

• the vehicle must also have a good alternator and a strong battery. if you have to occasionally jump-start your vehicle, all of the memory from the powertrain control module (pcm) is erased, which includes the data that accurately tracks the results from various stages of the drive cycle. also, if the battery is weak or undercharged, some of the most important tests will never run.

• the vehicle must sit overnight, or for at least eight hours, in an environment that is less than 90° f. the engine temperature needs to match the air temperature in order to establish an accurate baseline for the testing. if the outside temperature is over 90° f, the fuel is too volatile and the evap system won't even try to run its tests, though some of the other emissions systems may run their tests.

• the keys must be out of the ignition and all of the doors must be closed while the vehicle sits over night because many of the onboard computers "boot up" when the keys are in the ignition. also, many of the onboard computers still run until all of the doors are closed after the vehicle is shut off and the keys are removed.

step two: the cold start

• start the vehicle and let it idle for two to three minutes in park or neutral. while it is idling, turn on the head lights, heater/defroster, and rear defroster for a three to five minute warm-up phase. let the idle speed settle down to near the normal speed.

• next, put the vehicle in gear and drive through city streets at about 25 mph. go up to about 35 to 40 mph a few times before slowing down to stop. don't roll through the stop; be sure the car is really stopped, just like you learned in driving school. accelerate from each stop in a normal fashion—not overly conservative, but not like you are competing in a drag race either.

step three: a short freeway trip

• after the vehicle has been cold started and driven for a few miles on city streets, the next step is to take it on a short freeway trip.

• enter the freeway on-ramp and allow enough room with respect to other vehicles so that you can do a 1/2 to 3/4 throttle acceleration up to freeway speed.

• when you have accelerated up to around 60 mph and have safely merged into the flow of traffic, stay in the slow lane and maintain a steady speed of 55 to 60 mph for a minimum of five miles. please use the cruise control to help you maintain speed.

• find a nice, long off ramp to exit from the freeway. as you exit, take your foot off of the accelerator and let the vehicle coast down until it stops under its own power as you complete your exit from the freeway. do not use the foot brake and do not shift gears until the very end of this "coast down" phase.

step four: more city driving

• after you have completed the freeway trip, drive through the city streets for a repeat of the second part of step two.

• go up to about 35 to 40 mph a few times and then maintain a city speed of 25 mph before slowing down to stop. again, don't roll through the stop and make sure to accelerate normally.

• pull in to a parking place and let the engine idle for one to two minutes and then shut it off.

step five: have your readiness monitors checked and verified

• drive your vehicle to your regular shop and have them re-check your readiness monitors, present codes, and pending codes. they should do this as a courtesy and for free.

• if all of your monitors are "ready" and there are no present or pending codes, then your vehicle has been properly repaired and is ready for an emissions inspection and for normal driving.

• if your monitors are not ready, please click here for more information.

Most engine builders appreciate how important good oil pressure is for proper engine lubrication and longevity. They also know that low oil pressure can cause engine noise, bearing failures and customer complaints that result in expensive warranty claims. Considering how important oil pressure is for all of these reasons, why would anyone take a chance on reusing a high-mileage oil pump when rebuilding an engine?

Old oil pumps are usually worn with sloppy internal clearances and reduced output. Wear between the gears, the gears and the housing, and the gears and the pump cover provide leak paths that can hinder a pump’s ability to generate normal flow and pressure. Pulling the cover off the pump and sanding or grinding it flat can help tighten up the end clearance between the gears and cover, but it won’t do anything to restore clearances between the gears or the gears and the housing.

The pressure relief spring in a used pump can have millions of compression cycles already applied, and if reused, will run a high risk of failure. A broken spring will allow the pressure relief valve to stay open, greatly reducing the flow output of the pump.

Front-mounted pumps, which are driven by the crankshaft, have machined features called “sacrificial nodes” or rings. These features are used to center the pump to the crankshaft at the engine assembly plant. Due to the design, these will become partially deformed by the crankshaft (hence the term sacrificial) during normal engine operation. So, a used oil pump will have these centering features deformed, which will make centering the pumps to the crankshaft very difficult, if not impossible.

A brand-new oil pump is just as important as new bearings, rings, gaskets and timing chains or belts. Most brand name pumps will have the proper clearances out of the box. Even so, it’s always a good idea to disassemble the pump and check internal clearances with a feeler gauge prior to installing the pump to make sure the clearances are correct. If a pump has too much clearance, take it back and get another or try a different brand. Be sure to reinstall the gears and rotors just as they were removed from the pump. Some internal pump components are not symmetrical, and if installed incorrectly, will lock up when the cover screws are torqued to the proper specification.

Something else to keep in mind with respect to new pumps is that disassembling the pump will void the factory warranty!

High-mileage oil pumps usually have a lot of wear inside. That’s no surprise. However, some new pumps can also have excessive clearances. Always check clearances to make sure they are within tolerances before installing the pump.

Oil Pump Upgrades

For a performance engine build, upgrading to some type of performance pump is usually a good idea. This might include a high-volume pump and/or a billet pump for added strength and durability.

Many engines don’t need a high-volume pump because a stock pump will usually generate enough flow and pressure, but there are exceptions. Engines built with looser bearing clearances, piston oilers and/or extra oil lines for upper valvetrain roller rockers or shaft rockers will require a higher volume pump. The same goes for late-model production engines that have cylinder deactivation and/or variable valve timing. They also require higher-flow oil pumps.

Don’t confuse high volume with high pressure. High pressure just means the pump’s relief valve has a stiffer spring that requires higher system pressure to operate. Once the pressure is obtained, some of the output oil flow will be rerouted back to the inlet of the oil pump.

Most engines only need about 10 psi (or less) of oil pressure for every 1,000 RPM, and many engines can get by with as little as 5 to 7 psi per 1,000 RPM.

Oil pumps can use quite a bit of power — as much as 2.5 to 5 percent of the engine’s output — especially at higher engine speeds. That’s quite a power drain, so some late-model engines are now equipped with energy-saving variable displacement oil pumps. A conventional, fixed-displacement oil pump churns out the same volume of oil regardless of how much the engine actually needs. Its output is directly proportional to engine RPM and increases with speed.

By comparison, a variable displacement pump has a vaned rotor mounted on a crankshaft-driven eccentric. It works much like a variable displacement A/C compressor. The vanes rotate and sweep oil from the inlet side to the outlet side. By changing the relative position of the eccentric inside the rotor, or by rotating the outer housing, the relative volume on the inlet and outlet sides of the rotor can be changed to vary the pump’s output. The pump may be spring-loaded to vary pressure, or it can be controlled by the engine computer via an external solenoid. The latter uses a pulse-width modulated signal to fine-tune the pump’s output.

The aluminum or stamped steel covers on some OEM front-mounted oil pumps experience quite a bit of flex under pressure. This can cause oil pressure to fluctuate or even drop at higher engine speeds. Aftermarket replacement pumps for many of these applications have more rigid cast iron covers to improve pressure tightness and priming.

If Oil Pressure is Low

If a customer complains that the engine you built for him is not developing good oil pressure, any of the following could be a contributing factor:

• You cut corners and reused a worn, high-mileage pump — big mistake! Now you’ll have to replace the pump at your own expense!

• You installed a new pump, but did not check its internal clearances to make sure it was within acceptable tolerances. That’s partially your fault and partially the fault of the pump supplier. You’ll know better next time!

• Not all the parts were installed. Case in point: GM LS engines have two oil galley plugs — one under the front timing cover and the other under the rear. Forgetting either one or installing the barbell backwards (O-ring seal goes to the outside) will result in low oil pressure.

• The oil pump has a pressure relief valve that is leaking or stuck open. The underlying cause might be a weak or broken pressure relief valve spring, or more likely, debris in the relief valve that prevents it from closing.
  One oil pump supplier told us about a problem he’s seen with various spin-on oil filters causing a loss of oil pressure with new oil pumps.

When the filter is installed, any loose debris that is on the outlet side of the filter will be pushed into the engine and will eventually end up back in the oil pan where it will be sucked into the oil pump. Remember, oil pumps run on unfiltered oil. The mesh screen on the pump pickup tube is not fine enough to stop debris that is smaller than the holes between the wires in the screen.

When the debris enters the pump, some of it may be pushed out through the pressure relief valve. It only takes a tiny bit of debris to jam the relief valve open or prevent it from fully closing, causing a loss of oil pressure to the engine.

If you have a new oil pump that isn’t developing normal oil pressure in an engine, remove and disassemble the pump to inspect the pressure relief valve. If the valve contains any debris, you either have a faulty oil filter that is shedding debris into the oil supply or there are contaminants in the oil from another source.

To prevent filter-related contamination, always inspect the inside of a new oil filter BEFORE it is installed. Turn the filter upside down and bang it on your work bench to dislodge any loose debris that might be inside or use pressurized air to blow it out. An ounce of prevention can prevent a lot of headaches down the road. If you have installed a new oil pump and the pressure is still low, these could be the possible problems:

• Oil leaks in any part of the pressurized oil system (oil filter, oil pump to block mounting, oil galleys, etc.). Most factory crankcase-mounted oil pumps do not have a gasket between the pump and block. This junction can leak oil if the mating surfaces are not perfectly flat.

• Defective oil-pressure-sending unit or oil pressure gauge. Many so-called “bad” oil pumps are replaced unnecessarily because the real problem is a bad sending unit or gauge. Check oil pressure directly at the sending unit port on the block with an accurate gauge to confirm oil pressure. If the reading is good, the problem is a bad sending unit or gauge, not a bad pump.

• The oil pump is having problems sucking enough oil through the pickup screen and inlet tube. This type of problem will be worse when the engine is cold, and it may be due to oil that is too thick for the application or a pickup screen that has too fine of a mesh that is creating a restriction.

• If oil pressure is dropping off at higher engine speeds in a racing application, the diameter of the pickup tube may be too small for the volume of oil that the pump is attempting to pull from the pan. Switching to a pump with a larger pickup tube may be necessary.

• Sometimes a low oil pressure problem isn’t an oil pump or internal leak problem, but a combination of loose bearing clearances and the wrong oil.

Oil pump relief valves are spring-loaded and vent oil back into the crankcase when internal pressure exceeds spring tension. Debris in the oil can jam the relief valve open or prevent it from fully closing, causing a loss of oil pressure.

Pump Replacement and Priming

Crankcase-mounted oil pumps are usually self-priming because they are submerged in oil inside the pan, but front-mounted pumps are mounted high and dry and typically take longer to self-prime. Both types of pumps should be presoaked in oil before they are installed. Equally important is pressure priming the engine’s oil system prior to its first start-up.

Front-mounted pumps also require carefully centering the pump on the crankshaft before tightening the pump’s mounting bolts to the block. If the pump is off-center, even slightly, it may bind up and fail when the engine is cranked or started.

One way to center a front-mounted oil pump is to install the pump on the block with the mounting bolts finger tight then crank the engine over several times so the pump can center itself on the crank. The pump-mounting bolts can then be tightened to final specifications.

Another method for centering the pump to the crankshaft is to stand the engine block up on end. This will center the crank in its main bores. The front-mounted pump can then be mounted and centered using a feeler gauge before tightening down the bolts.

Finally, many experts warn against reusing high-mileage oil pickup tubes and screens. Why? Because they are difficult to clean internally and there may be debris left inside. In addition, varnish buildup on the wire mesh reduces the effective open area of the pickup, which will impact the amount of oil flow through the wire mesh. A varnish coating of .005˝ can reduce the open area by 25%.

High-mileage oil pumps usually have a lot of wear inside. That’s no surprise. However, some new pumps can also have excessive clearances. Always check clearances to make sure they are within tolerances before installing the pump.

To avoid timing belt failure and related engine damage, talk to your customers about the importance of timing belt maintenance. These facts and figures will give you all the data you need to keep your customers up and running.

Timing belts by the numbers

On average, timing belts should be replaced at 90,000 miles *Always refer to the manufacturer's suggested replacement interval

Inspecting the timing belt can save 1,000s of dollars in repairs

#1 cause of wear: heat

Four basic components of a timing belt - belt, idler pulley, tensioner and water pump

Timing belts are different

Use these diagrams to explain the importance of timing belt maintenance.

Evaluating your timing belt

An important consideration remains, how much work is involved in getting to a timing belt. So, other engine maintenance - such as water pump repair, coolant replacement and the examination of other belts and components - are the best opportunities for technicians to evaluate the timing belt.

A defective timing belt cover can let in oil, water or dust. (repair ASAP)

But aren't there any clues?Warning signs include noises like grinding, knocking and squealing. These noises can indicate high or low belt tension, a defective bearing or a misalignment.

Change the whole system when you replace the belt. (aka fix it and forget it)

Check it right:

Oil and coolant leaks

Leaking within bearing seal

Noise issues

Engine roughness

Abnormal belt appearance

Pulley wear or failure

Hydraulic tensioner failure

Misaligned belt

High mileage

*A simple visual inspection may not reveal pulley or tensioner bearings on verge of failure. Belts fail from the inside out.

CHECK IT WHEN YOU CAN:
If belt is visible, inspect at every oil change. Detect misalignment, tooth separation, missing teeth, and/or "shiny" belt. Look for cracks. Understand current mileage of the vehicle and service history of the timing belt drive system.

e only constant in the oil change business is change itself, especially if you’re trying to maintain an inventory of engine oil for all makes and models of vehicles. Since Volkswagen began ­requiring application-specific engine oil in the mid-1990s, the oil change business has (pardon the pun) “changed.” While many Asian vehicles ­currently require only a universal 5W-30 motor oil, European manufacturers have leaned toward ­requiring more application-specific engine oils.

The trend has spread to the domestic manufacturers as well, with Ford Motor Company requiring specific engine oils for a number of its engines and General Motors requiring its Dexos or its licensed equivalents for use in its current generation of vehicles. Many high-end and high-performance nameplates from any auto manufacturer often require synthetic or application-specific synthetic oils as well. See Photo 1.

The Driving Force Behind Oil Change Evolution

Photo 1: We’re probably going to see more oil caps ­indicating the need for an
application-specific engine oil.

Synthetic and lower-viscosity engine oils have been used since the 1980s to increase fuel economy. During the late 1990s, Ford Motor Co. and Honda Motor Co. began requiring 5W-20 for many of their new engines to increase fuel economy and to deal with several different piston ring issues. General Motors, which also manufactures on a global basis, began requiring its Dexos brand to meet ­extended oil change interval requirements for its ­latest generation of ­engines.

As you might suspect, improved engine ­designs are the driving force behind increasingly stringent engine oil requirements. Turbocharged diesel engines have their specific lubrication ­requirements, as do engines equipped with variable valve timing (VVT) and gasoline direct ­injection (GDI). For example, the extreme thermal and mechanical stresses in a compression-ignition diesel engine ­increase the demands on engine oil. Diesel engine oils must withstand extremely high thermal stresses as well as very high concentrations of soot ­produced by combustion.

VVT engines similarly not only require a ­specific oil viscosity, but also require an oil that keeps the pulse-modulated variable valve timing solenoids clean, well-lubricated and free of small air bubbles caused by oil foaming. See Photo 2.

Photo 2: Although the
oil screens on this variable valve timing (VVT) solenoid appear clean, they’re actually clogged with varnish from oxidized engine oil.

GDI engines also have some unique ­engine oil requirements, the most notable of which are the anti-scuffing properties that are needed to prevent damage to the camshaft fuel pump eccentric and cam follower on the high-pressure mechanical fuel pump. When generic engine oils are used, the camshaft eccentric eventually begins galling, as illustrated in Photo 3.

In addition, GDI engines also tend to contaminate the engine oil with excessive amounts of ­carbon that, according to some studies, tends to ­increase timing chain wear.

Lastly, some GDI ­engines are designed with up to 14:1 compression ratios. In most GDI designs, detonation is controlled by variable valve timing and by modifying the direct fuel injection timing mode. But researchers have found that, on some engines, very small droplets of engine oil creep past the ­piston rings and cause detonation, which mechanically damages the piston rings and lands.

In some instances, engineers have changed the PCM’s operating strategies to decrease detonation tendencies and, in other instances, lubrication engineers are working to solve detonation problems by changing the oil formulation.

Oil Formulations

Photo 3: Non-specification ­engine oil has scuffed this high-pressure fuel pump ­eccentric used on gasoline ­direct injection engines.

How do lubrication engineers change the properties of engine oil? According to one leading ­lubrication journal, there are four major additive manufacturers and up to 20 paraffinic base oil stock suppliers in North America. In the U.S. and Canada, we also have about 227 ­companies licensed to sell API SN engine oils.

The complexity of today’s ­engine oil market is perhaps best illustrated by General Motors’ Dexos 1 website www.centerforqa.com/gm/dexos1-brands. ­Although considered a “domestic” auto manufacturer, General Motors actually manufactures vehicles in 34 countries and markets vehicles in 140 countries. According to the website, many different brands of oils are now licensed to ­display the Dexos logo on their containers.

Notice that 5W-20 and 5W-30 are the only ­viscosities supplied, with Dexos 1 being used in gasoline engines and Dexos 2 in diesel ­applications.

Under “About Dexos,” the website explains why the Dexos specifications exceed those of the ­various oil rating ­organizations. Further note that many licensed brands are ­approved for use only in specific geographic locations, such as “Global,” “North America,” and “North America and ­Europe.”

Labeling is, of course, another caveat in choosing the correct engine oil for a specific application. A phrase such as, “meets OE specifications” is not equivalent to “OE-approved” or “OE-­licensed.” An engine oil might also include in its labeling a phrase indicating that it meets an OE alpha-numeric specification number. In any case, choosing the correct engine oil for a specific ­application can be tricky so, when in doubt about an aftermarket oil, it’s best to choose the OE-branded oil.

Oil Filtration

Photo 4: The oil filter bypass spring is located at the bottom of the filter, while the anti-drain back valve is the rubber washer located at the top.

Choosing an oil filter that will meet OE requirements for extended oil changes is as important as choosing the correct engine oil. The basic parameters are valving, capacity, micron rating and efficiency. Any OE-equivalent oil ­filter should, for example, contain an anti-drain back valve and an oil filter ­bypass valve. The anti-drain valve simply prevents the oil from draining out of the engine’s oil galleries, through the oil filter and back to the oil pan when the engine is shut off.

While it’s been many years since I’ve encountered oil filters lacking an anti-drain valve, ­filters lacking anti-drain protection usually cause excessive ­engine noise during startup due to a slow build up of oil pressure. The oil filter bypass valve is critical because, in the event that the oil filter media clogs, the bypass valve allows ­engine oil to flow directly from the oil pump to the engine oil galleries.

The oil filter media itself must have enough ­filtering capacity to continue trapping dirt and ­debris throughout the extended oil change interval. Filters lacking filtering capacity will prematurely clog during the extended oil change interval, causing the bypass valve to open, which ­allows dirt and debris to contact engine crankshaft bearings and other wearing surfaces. The ­bypass mode most often occurs during startup when the engine oil is cold. See Photo 4.

Lastly, it’s important to differentiate between the micron rating of an oil filter and its efficiency rating when filtering oil. While the micron rating ­indicates to a millionth of an inch the size of particle that can be trapped by the oil filter, the ­actual efficiency rating indicates how well the ­filter cleans the engine oil as it passes through the oil filter media.

So, while two ­filters can have the same micron rating, the actual efficiency rating might vary widely between the two filters. In any case, oil ­filters must be able to endure modern extended oil change intervals. Using a substandard or non-OE equivalent filter simply ­defeats the purpose of using an OE-­licensed engine oil.

Although the oil screens on this variable valve timing (VVT) solenoid appear clean, they’re actually clogged with varnish from oxidized engine oil.

Non-specification ­engine oil has scuffed this high-pressure fuel pump ­eccentric used on gasoline ­direct injection engines.

The oil filter bypass spring is located at the bottom of the filter, while the anti-drain back valve is the rubber washer located at the top.

Ballpark Numbers

Oil consumption has become an issue because oil change intervals now extend to 10,000 or more miles and because modern engines consume so little oil that many vehicle owners forget to regularly check their engine’s oil level. Worse still, many owners will often run their engines out of oil because they don’t know how to check the oil level. For that reason, oil level warning systems are becoming standard equipment for many vehicles.

That said, I don’t know of any specific number that would indicate excessive oil consumption for any specific vehicle. A ballpark number for oil consumption on a new engine might be a quart of oil during initial break-in. After break-in, oil consumption should then stabilize at perhaps one quart per 2,000 or 3,000 miles. For engines with 150,000 or more miles on the odometer, consuming one quart of oil every 2,000 miles should not be an issue. As engines wear, the combined loss from external and internal oil leaks might increase oil consumption to one quart per 1,000 miles, which should not be a problem if the spark plugs don’t become fouled with oil ash or the exhaust doesn’t emit visible oil smoke.

Internal Oil Consumption

Assuming that the engine has no obvious external leakage at the crankshaft seals, oil pan, timing cover or cylinder head and camshaft cover gaskets, let’s consider how engine oil might enter the combustion chamber through internal leaks. An example of internal leakage is turbocharger shaft seals leaking oil into the engine intake, as indicated by the coating of engine oil inside the ducting between the turbocharger and engine. If the intake manifold on some V-block engines seals the upper crankcase, oil can enter through one or more intake port gaskets. Similarly, worn or cracked intake valve stem seals can leak oil through the valve guides, especially during deceleration and extended idle-speed operation.

In either case, the spark plugs might show some oil ash accumulation on the side of the electrode facing the intake valves. Oil leakage through the exhaust valve guides isn’t as common since normal exhaust flow generates positive pressure. On the other hand, most oil consumption is through the pistons and piston rings, which is where our story goes next.

Cylinder Sealing

Oil washing is an indication of engine oil passing through the piston rings (see Photo 1). To better understand ring-related oil consumption, let’s look at piston and piston ring design. For example, many top rings are flat with a convex or barrel-shaped outer edge that contains a molybdenum inlay. The moly inlay retains oil and is resistant to high combustion temperatures.

Photo 1:Oil wash around the edges of this example piston dome is an indicator of oil passing through the piston rings.

The second compression ring not only helps seal combustion pressures, but scrapes excess oil into the engine crankcase (see Photo 2). In contrast to the top ring, the second ring is saucer-shaped, with only the bottom edge of the ring contacting the cylinder wall. When combustion pressure increases, the second ring flattens against the piston ring land, which forces the full outer width of the ring against the cylinder to seal combustion gases inside the cylinder. When not under load, the ring returns to its saucer-shaped configuration, which causes the lower edge of the ring to scrape excess back oil into the crankcase.

Photo 2: The second compression ring serves a dual purpose: sealing combustion pressures and helping keep engine oil out of the combustion chamber.

The bottom or third piston ring’s sole duty is to scrape excess engine oil into the crankcase. In most cases, the third ring is a three-piece design consisting of a vented ring expander and two steel rails that fit over the expander. The vented expander and piston ring groove allow excess oil to flow to the inside of the piston and into the crankcase (see Photo 3).

Photo 3: As seen in this photo, a collapsed oil control ring expander and worn oil control rings are indicated when the oil control ring assembly is flush with the piston ring land.

To help meet emissions standards, manufacturers have reduced piston-to-cylinder clearances. Using a 2013 Mazda 2.5-liter, 16-valve Skyactiv engine as an example, 0.0010” minimum and 0.0017” maximum is the standard specified clearance between pistons and cylinders for new engines.

To compare, clearances were nearly double that in older engine designs to allow for thermal expansion. Since modern high-silicon content aluminum pistons experience much less thermal expansion, 0.001” provides sufficient oil clearance between the piston and a precision-machined cylinder. These tight piston skirt clearances and precision-machined cylinders also hold the piston rings square with the cylinder wall for a much better compression and oil ring seal (see Photo 4).

Photo 4: The scuffed thrust side of our example piston suggests that the engine ran out of oil at some point.

In the meantime, most light-duty engines reduce rotating friction by using narrow, low-tension piston rings. Low-tension piston rings also tend to last longer due to less circumferential pressure against the cylinder. Last, improved cylinder boring and “plateaued” cylinder honing techniques allow the piston rings to quickly seat into the cylinder wall. After break-in, a coarser, underlying cross-hatch pattern remains in the cylinder to keep the piston rings and upper cylinder areas well lubricated.

Engine Oiling

Connecting rod bearing clearance affects oil consumption because the piston and cylinder are splash-lubricated by oil passing through the connecting rod bearing and onto the cylinder wall. With our Mazda SkyActiv engine, oil must pass through an 0.0011” to 0.0020” connecting rod bearing clearance before it can reach the cylinder wall. Remember that doubling the connecting rod bearing clearance will quadruple the oil flow to the piston rings, which can dramatically increase oil consumption.

The engine oil must then pass through 0.0001” of an inch oil clearance between the piston skirt and cylinder before it reaches the piston rings. Using high-viscosity oil in a new engine reduces the lubrication and cooling of low-tension piston rings, which can be a serious problem on today’s turbocharged, high-performance engines.

Another issue with using high-viscosity oil is that it might prevent low-tension piston rings from contacting the cylinder wall, which can increase oil consumption.

As mentioned above, oil slinging off the crankshaft not only lubricates the rings, but cools them as well. Since high-viscosity oil reduces oil flow through the connecting rod bearing, cylinder lubrication and cooling will be negatively affected.

While on the one hand we’re trying to reduce oil flow to the piston rings, on the other hand, the oil film must reach the very top of the cylinder wall. High-viscosity generic oils might not adequately lubricate the top and second piston rings, especially during cold startups. The flash point of the oil must also be high enough to resist vaporizing under high cylinder wall temperatures. Using non-synthetic base oils in synthetic applications allows this oil film to be burned away during combustion, whereas synthetic oils tend to remain in place in the upper cylinder.

In practically all cases, synthetic oils not only protect the upper cylinder, but also protect the top and second piston rings from momentarily micro-welding to the cylinder wall during high-load driving conditions. As miles accumulate, synthetic oils also keep pistons free of varnish deposits that can cause low-tension piston rings to stick in their grooves.

In summary, following the recommended maintenance intervals and using specified engine oils goes a long way toward preventing excessive oil consumption on modern engines.

Diagnostic Solutions: We Should Know It When We See It

1. All engines consume oil, so check the oil level before the oil is drained. Compare the mileage on the odometer with the mileage on the lube sticker to estimate the engine’s oil consumption rate, which should be noted on the vehicle owner’s lube and inspection report.

2. Free underhood engine oil and fluid level checks for your customers will generate a positive image for your shop.

3. Oil flows downhill. When the vehicle is on the lift, use a bright flashlight to examine the engine, beginning with the camshaft or rocker arm covers.

4. If there’s oil dripping from the bellhousing area, remember that automatic transmission oil is usually red while engine oil is black or brown. Check the level of each to help determine the source of the leak.

5. A large puff of blue oil smoke from the exhaust after an extended idling period usually indicates internal engine oil consumption caused by worn piston rings, valve seals, intake manifold gaskets, or clogged oil drains in the cylinder head.

6. Oil consumption with no apparent oil smoke often indicates collapsed oil control ring expanders or worn oil control rings.

7. Poor lubrication can cause modern piston rings to overheat and lose their tension. When combined with excessive varnish, the piston rings can stick in a collapsed position.

8. Excessive compression ring blowby will force engine oil into the intake air ducting or intake manifold.

9. A combination of low-speed driving and neglected oil changes on variable displacement engines can cause the piston rings to stick in their grooves on the deactivation cylinders.

10. Crusted oil ash deposits on spark plugs and upstream oxygen sensors are the best indicators of excessive internal oil consumption.

Challenge:

Exhaust flanges that are improperly tightened or torqued can cause many problems. These include exhaust system leaks and associated component failure, like gaskets and studs, and premature system fatigue and failure.

Solution:

Progressively Tighten Bolts on Flanges Flanges are found on a variety of parts associated with exhaust repairs. Each has its own process for achieving proper torque and successful installation. In general, all nuts are secured following a progressive, higher torque sequence. For example, the nuts require 60-ft.-lbs. of torque. Begin by torquing nut one, two and three to 20-ft.-lbs. Then, tighten all three nuts to 40-ft.-lbs., and finish by tightening each to 60-ft.-lbs.

For Y-Pipes:
It’s important to secure both sides of the Y-pipe simultaneously. Begin by tightening nuts down in a rotating sequence between both pipes. It is also necessary to alternate between both flanges found on the Y-pipe.

For Manifold Converters:
Typically, the tightening sequence begins in the middle of the manifold, while working your way out evenly between both sides. Be sure to review manufacturer’s recommended torque sequence for each application.

IMPORTANT:
In all installation instances above, tighten all studs evenly throughout the process.
Always evenly alternate between both flanges found on the Y-pipe while following the proper sequence on each individual flange.

Most serpentine belt requests occur after the customer notices the squealing or chirping noises. These are commonly associated with improper belt tension and misalignment. However, replacing the belt alone rarely resolves the issue. The best way to prevent comebacks and “defective” belt claims is to replace the tensioner assembly and associated pulleys, and recommend a thorough inspection of the other belt-driven components.

A worn or glazed serpentine belt may begin to squeal with age. Squealing from a newly replaced belt usually indicates a larger problem: Improper Tension. The automatic belt tensioner is designed to provide constant tension for the life of the belt. Heat and repeated cycling of the tensioner’s internal spring can lead to fatigue and loss of tension. Loss of lubrication, as well as foreign contaminants inside the tensioner housing, may cause binding and limit the full travel of the tensioner arm. These can compromise the effectiveness of the tensioner by providing too little (or too much) tension. Overtensioned belts rarely squeal, but can cause other issues. Squealing is primarily due to slippage, and is the most noticeable symptom of low belt tension.

The belt tensioner not only provides the proper amount of tension, but also absorbs shocks and vibrations from the rest of the drive system. A damper inside the tensioner housing reduces the motion of the tensioner arm, while absorbing vibrations and reducing noise. Excessive oscillation of the tensioner arm is a symptom of damper failure and spring fatigue. It also may be an indication of component failure elsewhere in the accessory drive system.

Serpentine belt misalignment can be caused by any of the accessory pulleys. Or, it may be the result of improper belt installation. There are two types of misalignment, each caused by the relationship of the pulleys to one another.

Angular Misalignment

This occurs when pulleys become “tilted” because their shafts are not parallel. Worn bushings and bearings can allow rotating shafts to become cockeyed in their bores. Premature bearing and bushing wear is often caused by the strain of excessive belt tension. Installing a belt that is shorter than the original, or attempting to bypass a component like an A/C compressor, can alter the amount of tension. This can reduce belt life and accelerate wear on other components. Likewise, substituting larger pulleys can have the same effect, as well as decrease the output of alternators and power steering pumps. Angular misalignment can also originate from the tensioner itself as the internal pivot bushing wears and the tensioner arm begins to tilt. This also may cause binding between the housing and arm, which leads to tension issues.

Parallel Misalignment

When a pulley is “out of plane” with the other pulleys in the drive system, parallel misalignment occurs. While all of the pulleys may be running true, one or more of them could be sitting too far forward or back on its shaft. A common source of parallel misalignment is improper installation depth of press-fit pulleys, like those found on power steering pumps. The outer ring of a worn harmonic balancer may begin to “walk” from its hub, causing a similar misalignment. In either type of misalignment, the belt will track at an angle, leading to increased wear on the ribs and belt edges. The added friction also increases the operating temperature of the belt. This can drastically decrease belt performance and service life. Misalignment angles of as little as three degrees can cause an annoying chirp as well as increase the chances of the belt jumping its pulley. Insufficient belt tension adds to the likelihood of belt loss.

Misalignment (and the resulting noise) is most pronounced on short spans between pulleys. Diagnosis of longer spans can be difficult. A few degrees of offset may not be obvious to the naked eye. The use of a laser alignment tool or straightedge can be helpful in finding these little variations

Sensors provide the inputs the Powertrain Control Module (PCM) needs to make critical control decisions. They are like the nerve endings of the vehicle. Without accurate input data, the computer may not make the correct command decisions. This, in turn, can cause emissions, performance and drivability problems.

Except for some early 1980s vintage oxygen sensors, most sensors have no factory recommended replacement intervals. They work until they don’t. In other words, they are designed to last the life of the vehicle or until they fail.

The Onboard Diagnostic (OBD II) system is capable of detecting most sensor faults if a sensor is not reading within its normal range or if the signal is lost altogether. If a fault is detected, the OBD II system will set a code and turn on the Check Engine light to alert the driver that something is amiss. In some situations, the OBD II system will set a “pending” code in its memory that does not turn on the Check Engine light, but will eventually turn the light on if the same fault happens on a subsequent trip.

 The Check Engine light is very confusing to most motorists because it doesn’t reveal anything about the nature of the fault. The motorist has no way of knowing if the problem is something serious or only a minor glitch. The only way to know what is causing the light to come on is to plug a scan tool into the diagnostic connector and read the code(s).

As a rule, the Check Engine light only comes on if a fault affects emissions. A bad sensor can certainly do that. However, the Check Engine light usually does NOT come on if the engine has quit running, if the engine is overheating, if the engine has a mechanical problem, if oil pressure is low, or if the oil needs changing.

Many motorists simply ignore the Check Engine light, especially if their engine seems to be running normally. But this is not a wise decision because some “minor” problems can have major consequences if ignored long enough. An engine that is misfiring because of a bad spark plug, weak coil, dirty fuel injector, leaky valve, or vacuum or EGR leak, may cause the catalytic converter to overheat and suffer damage. An engine that has a “lean” code such as P0171 or P0174 (which can often be caused by a dirty mass airflow sensor) is at greater risk of engine-damaging detonation when the engine is working hard under load.

Another reason for not ignoring the Check Engine light is that a vehicle with a Check Engine light on will fail an OBD II plug-in emissions test. There must be no codes present to pass the test. And if the vehicle doesn’t pass the required test, the vehicle owner can’t renew his vehicle registration when the license plate sticker expires.

To pass an OBD II emissions test, all of the OBD II system’s self-monitors must have run and completed before the vehicle is considered “ready” for testing. A bad sensor can prevent some OBD II monitors from running. An oxygen sensor code, for example, will prevent the catalyst monitor from running. The catalyst monitor needs good inputs from both the upstream and downstream O2 sensors to check the operating efficiency.

Oxygen Sensors

Oxygen sensors are one of the most often replaced sensors. Inputs from the O2 sensors are used by the engine management system to adjust the fuel mixture. This is critical for maintaining low emissions and good fuel economy. If an O2 sensor gets “lazy” because of old age or contamination, the computer may not be able to adjust the fuel mixture quickly enough as the engine’s operating conditions change. O2 sensors that are failing tend to read lean, which causes the fuel system to run overly rich to compensate. The result is increased emissions and fuel consumption.

The responsiveness of the O2 sensors can be tested using various procedures (making the fuel mixture rich or lean and watching the sensor’s response on a scan tool with graphing capability). If an O2 sensor is sluggish or unresponsive, it needs to be replaced. The same goes for any O2 sensor that has a bad internal heater circuit.

O2 sensor failures can be caused by various contaminants that enter the exhaust. These include silicates from internal engine coolant leaks (due to a leaky head gasket or a crack in a cylinder wall or combustion chamber) and phosphorus from excessive oil consumption (due to worn rings or valve guides). Replacing a fouled O2 sensor may temporarily solve the problem, but sooner or later the new sensor also will fail if the underlying problem that is allowing the contamination to occur is not corrected.

Identifying which O2 sensor has to be replaced also can be confusing. On most 1996 and newer V6 and V8 engines, there are at least two upstream O2 sensors, and one or two downstream O2 sensors. Some engines may have as many as six O2 sensors. A fault code for an O2 sensor will indicate the sensor location by sensor number (1, 2, 3 or 4) and by cylinder bank (1 or 2). Sensor No. 1 is usually the one in the exhaust manifold, while sensor No. 2 is usually the downstream O2 sensor behind the converter. Cylinder bank 1 is the same side that also has the number one cylinder in the engine’s firing order. Bank 2 would be the other side.

Replacement O2 sensors have to be the same type as the original with the same number of wires. If one O2 sensor on a high-mileage vehicle has failed, chances are the other O2 sensors may also be nearing the end of their service life and should be replaced at the same time to restore like-new performance.

Coolant Sensors

The coolant sensor keeps the PCM informed about the temperature of the coolant inside the engine. This is vital information for the PCM because many control functions vary with temperature. If the coolant sensor is faulty or is reading low, it can throw off the control system possibly causing it to remain in “open loop,” which is a temporary operating mode that should only occur following a cold start. A faulty coolant sensor, therefore, may cause the engine to run richer than normal, resulting in increased fuel consumption and higher emissions.

Input from the coolant sensor also is used to operate the engine’s electric cooling fan. No input or low input from the sensor may allow the engine to overheat because the fan isn’t coming on when it should be. Coolant sensors can be damaged by overheating, so if the engine has experienced an episode of severe overeating for any reason, replacing the coolant sensor is often recommended.

The coolant sensor’s output can be viewed on a scan tool as a temperature reading. It should match the air inlet temperature (IAT) reading when the engine is cold, and gradually increase as the engine warms up. The sensor’s resistance also can be checked with an ohmmeter and compared to specifications for various temperatures. If the sensor is not reading correctly, it needs to be replaced.

Throttle Position Sensors

The throttle position sensor (TPS) is mounted on the throttle body and monitors the position of the throttle opening. The TPS value is displayed on a scan tool as percentage of throttle opening. The PCM uses this information to estimate air flow and engine load. On newer vehicles with electronic throttle control, the sensor’s input also is vital for making sure the throttle is at the correct commanded position.

The PCM uses information from the throttle position sensor (TPS) to estimate air flow and engine load. Contact-style TPS sensors can develop a worn spot just above the idle position as the miles add up. This, in turn, may create a “flat spot” that results in momentary hesitation or stumble when the driver steps on the gas. This may not set a fault code because the glitch occurs too quickly for the OBD II system to detect.

The sensor’s out put can be checked with a voltmeter, or observed on a scan tool. If there are any drops in the output as the throttle opens, the sensor is bad and needs to be replaced. On some older vehicles, the idle voltage setting of the sensor must be adjusted to a specified voltage.

MAP Sensors

The Manifold Absolute Pressure (MAP) sensor monitors the pressure differential between intake vacuum and the outside atmosphere. The PCM uses this information to determine how much load is on the engine. If the engine has a “speed-density” fuel injection system that does not use a mass airflow sensor, input from the MAP sensor is also used with inputs from the TPS sensor to estimate airflow. Problems with this sensor can cause hesitation, fuel mixture and spark timing problems. The sensor’s output can be read on a scan tool, or checked by reading its frequency or voltage output on a DVOM. If the sensor is reading out of range, check the sensor’s connection to the intake manifold for a possible vacuum leak. If there’s no leak, the sensor needs to be replaced.

Mass Airflow Sensors

The Mass AirFlow (MAF) sensor is usually located between the air filter housing and the throttle. The MAF sensor uses a heated wire or filament to measure airflow into the engine. This is vital information for controlling the fuel mixture. The most common problem here is contamination of the sensor element with dirt or fuel varnish. A dirty MAF sensor will typically report less airflow than is actually occurring. This can cause a lean fuel condition, hesitation, and reduced performance. The sensor’s output can be observed on a scan tool and should go up as the throttle opens and airflow increases. A sluggish or unresponsive MAF sensor can often be restored to normal operation by cleaning the sensor element with aerosol electronics cleaner. **Do not use any other type of cleaning chemical as this may damage the sensor!** If cleaning doesn’t do the trick, the sensor needs to be replaced.

Crankshaft & Camshaft Position Sensors

The Crankshaft Position (CKP) sensor keeps the PCM informed about the relative position and rotational speed of the crankshaft. Many engines also have a Camshaft Position (CMP) sensor that helps the computer figure out the correct firing order of the engine. A failure of either sensor may prevent the engine from starting or running.

Two types of sensors are commonly used for these applications: magnetic sensors or Hall effect sensors. Magnetic sensors have a wire coil wrapped around a magnetic core. When the tip of the sensor passes over a notch on a ring attached to the crank, it changes the magnetic field and produces a small current. With Hall effect sensors, a reference voltage is supplied to the sensor by the PCM to detect notches in the crank wheel.

Crank sensors may be mounted on the front of the engine and read notches in the crank pulley or mounted on the block to read a notched ring on the crank itself. The cam sensor(s) if used, are usually mounted in the cylinder head(s) and read a ring on the camshaft(s).

Loss of a signal or an erratic signal will usually set a fault code. The resistance of magnetic sensors can be measured with an ohmmeter. If out of range, the sensor needs to be replaced. The sensor ring also needs to be inspected for damaged, missing or cracked teeth as any of these conditions can cause erratic sensor readings.

Speed Sensors

Most late model vehicles have several magnetic speed sensors. The Vehicle Speed Sensor (VSS) is usually located on the transmission output shaft and provides a signal that is proportional to vehicle speed. The transmission also has one or two additional internal sensors for monitoring the relative speeds of the main input and output shafts. On vehicles equipped with antilock brakes, there are usually Wheel Speed Sensors (WSS) to monitor each of the wheels.

Faults in speed sensor circuits usually tend to be wiring related rather than outright sensor failures. However, magnetic sensors can become fouled with iron particles that stick to the tip of the sensor. Sensor inputs can be viewed on a scan tool or checked by measuring their resistance with an ohmmeter. If the wiring is okay but the sensor is reading out of range, the sensor needs to be replaced.  On vehicles where the wheel speed sensor is an integral part of the hub and wheel bearing assembly, the entire hub must be replaced if the sensor is bad. The ABS system will not operate unless it has good signals from all of its sensors.

Temperature Sensors

The engine management system uses an Inlet Air Temperature (IAT) sensor to monitor air temperature because changes in air temperature affect air density, which in turn affects the fuel mixture. A sensor that is not reading accurately can upset the fuel mixture causing an increase in emissions and fuel consumption as well as drivability issues. The sensor’s output can be shown on a scan tool or measured with an ohmmeter. If out of range, the sensor needs to be replaced.

The heating ventilation and air conditioning (HVAC) system also use air temperature sensors to monitor air temperature within the passenger compartment. A bad sensor won’t turn on the Check Engine light because it does not affect emissions, but it can cause problems with regulating heating and cooling if it is out of range.

Tire Pressure Sensors

All 2006 and newer passenger cars and light trucks are equipped with tire pressure monitor systems (TPMS) to keep an eye on tire pressures. The system will alert the driver if pressure drops 25 percent or more below the recommended inflation pressure. Most TPMS sensors are mounted on the end of the valve stem inside the wheel, though some older systems use a large TPMS sensor attached with a steel band to the drop center inside the wheel.

TPMS sensors have an internal battery with a limited service life that may range from five to seven years. Once the battery goes dead, the sensor needs to be replaced. Replacement is usually recommended when the tires are replaced. TPMS sensors also can be fouled by some types of tire sealer products.

A TPMS sensor’s ability to generate a good signal can be checked with a special TPMS tester that energizes the sensor and listens for a radio signal back from the sensor. If a sensor has failed or is not reading accurately, it needs to be replaced. “Universal” aftermarket TPMS sensors are available for a wide variety of applications. Following replacement, a special relearn procedure must be performed so the TPMS system can relearn the position of each sensor correctly.

The hand wire splicing technique has been around for awhile, so I cannot take credit for inventing nor perfecting it.

Poor electrical connections cause heat. The longer the current flows through the connection, the hotter the connection will get. This in turn increases the resistance even more. The problem with a butt connector is that is one surface area. Since electricity flows “on” the wire strands rather than “in” them, this doesn’t make functional use of all of their surface areas. Using this hand splice method will allow for the wire to transfer more of its electrical effort than using a butt connector and will produce less heat.

Step 1: Strip back about 3/4 of an inch of insulation from both wires. Add a section of shrink tubing onto the wire. (Don’t forget this step… or you’ll regret it after you’ve finished the splice.) Divide the bare strands into two equal sections and form them into a “Y”.

Step 2: Holding a wire in each hand, take the “Y” and interlock the two wires together. But, leave room between the two “Y”’s large enough for the outer insulation from the “none” strip section of wire to easily pass through. Lay the “Y” sections down along the wire without bending them backward, straight and even with the wire. Find the edge of the gap you left in the “Y”’s (That thickness measurement of the outside insulation, just about halfway between the two wires).

Step 3: Using one hand, pinch down on that spot while taking the legs of the “Y” from the same side and stand them straight up 90 degrees from the splice. Now, using your other hand, with firm finger pressure rotate the two legs of the “Y” around the splice towards the opposite wire. If done correctly, the spacing you left between the two “Y”s will actually lie down and end up right where the insulation begins. Also, as you pinch and roll the bare wire, keep it snug as possible. You want to end up with it no larger than the outside diameter of the insulated sections.

Step 4: Now switch procedures from the right hand to the left and and stand the other set of “Y” legs 90 degrees and do the same crimp and turn all the way to the othe
r insulated section of wire.
When soldering, be sure not to soak the splice with solder. The solder is only to aide in holding the splice in place so it won’t unravel, and the shrink tubing
is for overall weather protection, and to shield the bare wire.Once you’ve got the hang of it, you’ll find that the splice is extremely strong even without solder or shrink tubing.

Done right, the splice should have plenty of mech
anical hold without soldering. For battery cable, 4 gauge and larger, crimp or soldered connectors are still the best method. But for the average gauge wire, this method works extremely well.
Give it a try, and when you’ve mastered the technique, try it on your friends and see how much effort it takes them to pull it apart, even without soldering it.

Today’s cars have become like a mobile network of control modules.  These control modules operate everything from the powertrain, braking, steering and suspension system to climate control, lighting, entertainment, communications and navigation. The technology is mostly incomprehensible to the average motorist, yet it provides all kinds of functions and capabilities that were not even on the radar a decade ago: things like Bluetooth connectivity, hands-free communication and email, automatic emergency braking, blind spot detection, adaptive cruise control, stability control, electronic steering and even key-less smart fobs that allow the vehicle to sense your approach, automatically unlock the doors for you and wake up the onboard electronics so you can be on your way.

To make such wonders possible, automotive engineers have created specialized control modules for all kinds of applications. Many motorists are somewhat familiar with the main modules in a vehicle such as the Powertrain Control Module or PCM, which used to be referred to as the Engine Control Module (ECM) or Engine Control Unit (ECU) because it was the computer that controlled engine functions such as spark timing, fuel mixture and emissions. PCM serves as a more descriptive term because the PCM on many vehicles also controls the transmission, which is part of the powertrain.

A Transmission Control Module (TCM) would be a separate control module for the transmission. It interacts with the PCM or ECM to make sure the transmission shifts at the appropriate speed and load.

The Body Control Module (BCM) is yet another major module that usually handles multiple tasks ranging from lighting and other electrical accessories to climate control, keyless entry, anti-theft duties and managing communications between other modules. The functions can vary greatly depending on the year, make and model of vehicle, and even its list of options.

This brings us to the “other” modules.  These modules aren’t very well known and most people don’t know about them until one fails and they have to get it replaced. These modules have all kinds of strange and confusing acronyms as each carmaker has come up with its own unique list of acronyms for the various modules they use in their vehicles.

A Real Gem
A typical example is a Ford GEM module (Generic Electronic Module). Ford started using these in the mid-to-late 1990s in various cars, minivans and light trucks. It is essentially a body control module it terms of what it actually does, though the list of control functions will vary depending on the vehicle application and its options. Some of the control functions include interior lighting, daytime running lamps, power windows, warning chimes and lamps, rear window defroster, windshield wipers and washers, perimeter anti-theft alarm, remote keyless entry and battery saver functions. The module may be located behind the fuse panel under the dash (Ford F-series trucks) or in the engine compartment near the power center.

If a Ford GEM module has to be replaced (which can happen if water infiltrates and corrodes the electronics inside the black box), it usually requires a part number that is specific to the customer’s vehicle. To further complicate matters, Ford says their GEM modules need to be programmed after they have been installed so they will function correctly. But some are simply plug-n’-play and will work right out of the box.
Many modules on many different makes and models of vehicles do require either reprogramming for a specific vehicle application or VIN code, or have to undergo some type of initialization or learning procedure (which may require a scan tool) after they have been installed before they will function normally. If a DIY customer doesn’t know this, they may think the replacement module you sold them is no good and bring it back with a warranty claim.

Play It Again SamAnother example of modularization would be the Mercedes “SAM” modules that divide up many of the subsystem electrical control functions in Mercedes C-Class and E-Class cars. There are two of these “System Acquisition/Activation Modules” in each car, a rear module (SAM-R) located in the trunk for electrical functions in the rear portion of the vehicle such as taillights, rear window defroster, door locks, etc.) and a front driver side module (SAM-D) in the engine compartment for the headlamps, front turn signals, wipers and other accessories. What each module controls will vary depending on the model year car and how it is equipped. The Mercedes SAM modules seem to be rather troublesome and can be easily damaged by voltage overloads and even battery disconnects. They also have to be reprogrammed after they have been installed.

Module ManiaListing all of the vehicle specific submodules would take too long. Instead here’s a short list of “other” modules classified by what they do. Many of these modules have a single dedicated function to perform, so they are relatively simple. But others can be nearly as complex as a PCM. To make matters worse, most of these modules may be located virtually anywhere inside the vehicle. Space is tight inside today’s electronics-packed vehicles, so engineers are often forced to locate the module wherever they can find a spot that hasn’t already been taken by something else. Finding a module’s location often requires looking it up on an illustrated component guide or wiring diagram.

Some of these other modules include:
● ABS/traction control/stability control module
● Airbag (SRS) module
● Alarm module (or chime module) for anti-theft system
● Cruise control module (if not integrated within the PCM)
● Electronic steering module
● Fuel pump control module
● Injector driver module (such as FSD/PMD modules on GM diesel engines)
● Instrument cluster control module (which may be part of the cluster itself or a separate black box)
● Keyless entry module
● Lighting module
● Remote start/immobilizer module
● Suspension control module
● Transfer case module (4WD)
● Wiper motor control module
● Vehicle communication module (such as GM OnStar module)
● Plus all kinds of “mini” modules for power windows, power seats, heated/cooled seats, power sliding doors, door locks, sunroofs, air flow control doors inside the Heating Ventilation Air Conditioning (HVAC) system, and so on.

More Modules Less WiringMuch of the hard wiring in today’s vehicles also has changed as a result of modularization. Many conventional wiring circuits have been eliminated altogether and replaced by Controller Area Networks (CAN) that allow various modules to share data and interact in ways that previously required hard wired connections or were not even possible. CAN networks started to appear in domestic cars back in 2003, and on some imports as far back as 1992 (Mercedes). Since 2008, CAN has been standard on all cars and light trucks sold in the U.S.

The basic idea behind CAN is that it allows data from many different systems to be shared via a common communication link, the data bus. Actually, most vehicles have two or three of these data buses that operate at different speeds (baud rates). Some share data at high speed and others share less important information at lower speeds. The data is coded so each module knows what to read and what to ignore.
The concept sounds complicated because it is. But it also simplifies the wiring by reducing the number of individual hard wired circuits that are needed in an accessory laden vehicle. That saves weight, bulk and cost (copper is rather expensive these days). Today’s average car probably has more than a mile and a half of wiring, according to one Delphi engineer. Without CAN, it could be much, much more.

Smarter Than The People Who Use ItOne of the benefits of so many modules is that today’s cars are smarter than ever before. The modules manage not only the powertrain, steering, suspension, brakes, climate control system and other subsystems, but also communications, navigation and safety (which can require very high data rates).

Active safety systems such as Volvo’s “City Safety” automatic braking system (introduced back in 2010 on the Volvo XC60) has an infrared laser camera mounted at the top of the windshield to monitor the road ahead. The camera is also used for adaptive cruise control and lane departure warning. It looks for reflective surfaces such as the taillights of another vehicle to identify obstacles and calculate the distance to that vehicle. If the City Safety system determines the rate of closure may result in an accident, it flashes an audible and visual warning to the driver. It also preloads the brakes in anticipation the brakes will be applied. If the driver fails to react in time, the system takes over and automatically applies the brakes, stopping the vehicle before it hits the object in front of it.

Even something as simple as opening a sliding side door on a minivan has changed. Opening a side door on a minivan used to be a simple manual task. You grab the door handle, pull it and slide the door open. With power sliding doors, it’s an entirely different process. Pressing the door switch sends a request to the Body Control Module (BCM), which then forwards an activation command to the power door control module that unlatches the door and energizes a small electric motor to pull the door open — but only if the transmission is in Park and the vehicle is not moving (a safety feature that is smarter than many of the people who are using it!).

GM’s OnStar system can monitor vehicle performance and even perform remote diagnostics when a problem arises. OnStar can even shut down the vehicle remotely if a vehicle is stolen and pinpoint its location for the police using GPS (Global Positioning System).

When Modules Fail
This highly sophisticated and complicated technology is wonderful as long as it is working. But when something goes amiss such as a module failure, communications bus failure or sensor fault, it can cause all kinds of problems sometimes in seemingly unrelated systems. The failure of a steering angle sensor may affect not only the electronic steering but also the stability control system since both need to know the position and turn rate of the steering wheel.

Diagnostics has become a major challenge for today’s technicians, and is totally beyond the abilities of most DIYers. The reason why is that it takes sophisticated diagnostic equipment, the know-how to use that equipment and lots of experience to correctly diagnose many module-related faults. Many modules are replaced unnecessarily because the real problem was misdiagnosed (things like bad grounds, loose or corroded wiring connections or low voltage).

Like the PCM, most modules have some type of self-diagnostics that should detect and report failures. The fault will log a diagnostic trouble code (DTC) and that code will be stored somewhere (the PCM or BCM) so it can be retrieved later with a scan tool.

An inexpensive DIY scan tool that can read OBD powertrain codes (“P” codes) and CAN communication faults (“U” codes) usually cannot access body codes (“B” codes) and other subsystem codes (though a few can read ABS and air bag codes). What is usually required is either a factory scan tool (which is expensive and only works on one make of vehicle) or a professional level scan tool (which is expensive but is supposed to cover a broad range of makes and models). But as many technicians have discovered, even some professional scan tools can’t access everything. There are often gaps in the tool’s data base that prevent it from reading certain subsystems and codes, or prevent it from running certain system self-tests. In such cases, the only way to access the information is with a dedicated factory scan tool.

The availability of modules also is a major issue, especially for older vehicles that car dealers no longer stock parts for. Various aftermarket suppliers can often provide remanufactured modules for many applications, but there are also a lot of gaps in coverage — and some modules may not be available anywhere except a salvage yard.

There are aftermarket companies that specialize in repairing all kinds of electronic modules, and this may be a repair option if a replacement module for a specific application is unavailable from aftermarket sources or a car dealer. The only drawback here is that some modules may be so badly corroded or damaged that they can’t be repaired. There also is the time-delay of sending the module in to have it repaired, and waiting to get it back (plus the added cost of shipping it).

One final comment about modules is this: You can’t tell much about a module’s condition or its ability to function by its external appearance unless it shows obvious signs of corrosion or damage (such as flood or fire damage, or physical damage from an accident). If there is no code that indicates the module has failed, a bad module is typically diagnosed by a process of elimination. Everything else is ruled out first (such as bad grounds, wiring faults, low voltage, bad sensor inputs, etc.) until the only remaining cause is the module itself. Many DIYers (and even some pros) don’t want to take the time (or don’t know how) to do the proper diagnostics, so they assume the problem must be a bad module because the module is the most complicated component in the system or circuit. That explains why electronic module returns are so high, and why so many modules that are returned under warranty have no fault found when they are tested by the supplier or remanufacturer.

Rotating electrical parts such as starters and alternators often have to be replaced on older, high-mileage vehicles. Fuel injection has helped prolong the service life of starters by allowing engines to start more quickly when they are cranked. Such is not the case with alternators. Higher electrical demands on charging systems have increased alternator failures.

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Starter Troubles
A starter that’s failing may crank the engine too slowly for a quick start, or it may not crank the engine at all. Often, the problem is not the starter but a low battery or a loose or corroded battery cable connection. So, check the battery charge and condition first.

A good battery should be capable of accepting and holding a charge from a battery charger, and should be at least 75 percent charged (12.5 volts or higher). If the battery’s voltage is low and it doesn’t take a charge, your customer needs a new battery. Load-testing the battery or using a conductance tester to check its ability to take and store a charge can also confirm the need for replacing the battery. The average service life of a car battery is only about four to five years, and can be shorter in hot climates. So also consider the age of the battery when evaluating its condition.

If a DIY customer is not sure what might be causing his cranking problem, offer to bench-test his old starter. If the starter passes the tests, the slow-cranking or no-cranking problem is obviously something other than the starter. He should check the battery, battery cables, starter relay and the starter circuit and wiring connections for possible faults. If the starter fails the tests due to low cranking RPMs, excessive current draw or it failure to spin at all, you can sell your customer a new or remanufactured starter with a high degree of confidence.

High resistance within the starter itself, worn brushes, or grounds or opens in the armature or coil windings can be cause excessive current draw. It can also result from increased internal friction due to shaft bushings that bind or an armature or magnets that are rubbing inside the starter.

A loose starter may crank an engine slowly, noisily or not at all. Loose bolts will make for a weak ground connection. The starter may also flop around, slip, chatter or fail to engage depending on how loose it is. Sometimes the engine won’t crank even though the starter will spin. This is usually an engagement problem due to a weak solenoid or a defective starter drive. A starter drive that is on the verge of failure may engage briefly but then slip. The starter drive has a one way overrunning clutch mechanism that you can check once the starter is out of the car (and replace if necessary). The drive should turn freely in one direction but not in the other if good. A bad drive will turn freely in both directions or not at all. If a drive locks up, it can over-rev and destroy the starter.

Charging Problems
The first sign of trouble when an alternator is failing is a low or dead battery. On a late-model vehicle, that can not only cause a no-start but also can cause the loss of “learned” data in the powertrain control module and other modules throughout the vehicle. In some cases, certain modules may not regain their normal function after the battery has been recharged because the module requires a special relearn procedure.

The output of the charging system on a vehicle can be checked with a digital voltmeter while the engine is idling. A charging system that is working properly should produce a charging voltage of somewhere around 13.5 to 14 volts at idle with the lights and accessories off (always refer to the vehicle manufacturers specifications). When the engine is first started, the charging voltage should rise quickly to about two volts above base battery voltage, and then taper off, leveling out at the specified voltage.

The exact charging voltage will vary according to the battery’s state of charge, the load on the vehicle’s electrical system, and temperature. The lower the temperature the higher the charging voltage, and vice versa.
If the charging output is low, the alternator can be bench-tested to see if it is good or bad. Make sure you use the correct wiring adapters for the unit and that all of the connections are made properly. The bench tester will check the alternator’s voltage and current output, and also look for “ripple voltage” or alternating current leakage that would indicate bad diodes inside the alternator.

If the alternator fails the tests, your customer needs a new or remanufactured replacement alternator. You might use the opportunity to recommend a higher-output alternator if the customer’s vehicle is equipped with a megawatt aftermarket sound system or other high-load electrical accessories.

If the alternator passes the tests, the problem is not the alternator but something in the wiring or the charging system control circuitry. High circuit resistance and ground connection resistance can cause low charging output. Circuit resistance can be checked by connecting a volt meter to the positive battery terminal and the positive terminal on the alternator. With the engine running and the headlights on, there should be less than half a volt voltage drop, and ideally less than one-tenth of a volt drop. A higher reading would indicate too much resistance. The same test can be repeated using the battery negative terminal and the alternator housing to check for excessive resistance on the ground side of the circuit.

If the wiring checks out okay, the problem could be in the voltage regulating circuitry inside the powertrain control module. On many late-model vehicles, charging output can be varied depending on operating conditions as well as electrical load. Problems with other sensor inputs or a defect in the control module itself may prevent the alternator from charging properly.

A slipping drive belt is another common cause of undercharging, especially with V-belts on older vehicles. Serpentine belts usually provide a better grip, but if the automatic tensioner is weak or stuck it can allow the belt to slip under load. Glazed streaks on the belt or belt noise when high-load electrical accessories are turned on with the engine idling can be signs that the belt is slipping.

Alternator slippage and undercharging can also be caused by a bad alternator pulley. Overrunning Alternator Pulleys (OAP) are used on a number of late-model import and domestic vehicles. OAP pulleys have a one-way clutch inside the center of the pulley that slips and allows the pulley to free-wheel when engine speed suddenly drops. This reduces noise, vibration and harshness in the belt drive system, but may cause a charging problem if the clutch slips when it should be gripping.

Another type of pulley is the Overrunning Alternator Decoupler (OAD) pulley. This type of pulley combines a one-way clutch with a torsion spring to decouple and absorb torsional vibrations in the belt drive system. This provides much quieter and smoother operation than either a solid pulley or an OAP, especially at lower engine speeds (from idle to about 1,500 RPM). But it also can cause slipping and charging problems if the clutch or decoupler spring is defective.

Alternator Replacement
Some replacement alternators come with a pulley already installed and some do not. If the replacement alternator comes with a pulley, make sure the pulley matches the original (same diameter, width and belt type). No pulley means your customer will have to swap the pulley from the old alternator to the replacement. Removing a conventional solid pulley usually requires a gear puller to pull the pulley off the alternator shaft. But on some applications, a threaded OAP or OAD pulley may be used and a special tool may be required to get it off.

OAP and OAD pulleys are more complicated and expensive than ordinary solid pulleys, but are installed on the alternator for a reason. Replacing an OAP or OAD pulley with a less expensive solid pulley is possible, and some replacement alternators come with a less expensive solid pulley installed rather than an overrunning clutch or decoupler pulley. But replacing an OAP or OAD pulley with a solid pulley defeats the purpose of the original pulley and may result in increased NVH, reduced belt and tensioner life and customer complaints.

When a new or remanufactured alternator is installed on a high-mileage vehicle, recommend a new drive belt too. Original equipment belts made of EPDM synthetic rubber are high-mileage belts capable of lasting upward of 100,000 miles. Unlike older belts made of less durable rubber, they don’t crack with age. But they do wear. It’s difficult to see how much the grooves on the underside of the belt may be worn, so belt manufacturers have created special belt wear tools that can check the depth of the grooves to reveal how much they are worn.

The operation of the automatic belt tensioner also should be checked to make sure it is working correctly and is capable of maintaining proper belt tension. Rust and corrosion can cause old tensioners to bind, and a weak or broken spring may prevent it from keeping the belt tight.

Like most other systems on late-model vehicles, charging systems have become smarter and more complex.

Today’s computer-controlled charging systems tailor the charging rate not only to the electrical demands on the battery and alternator, but also to changing driving conditions. That makes diagnosis much more difficult when something goes wrong. Alternators have one of the highest return rates of any repair part – often because of misdiagnosis. Bench testing an alternator on a test stand should verify whether or not its output is within specifications.

If the unit tests bad, your customer needs a replacement alternator. But if the unit tests good, the problem is something else such as a bad voltage regulator, PCM or wiring harness. Loose, corroded or damaged wiring terminals at the back of the alternator are common causes of charging problems. Wiring connectors and terminals may appear to be okay on the outside, but have loose, corroded or broken wires inside.

Other sources of trouble include loose, corroded or damaged battery cables and ground straps, blown fuses in the power center, or a blown fusible link in the wiring. Another source of trouble can be miscommunication or lack of communication between the PCM and alternator or regulator.

You can have a good alternator that is capable of producing the required charging voltage and current, but it may not work properly if it doesn’t communicate properly with the PCM. Another problem that sometimes occurs is that some “economy” reman alternators that are listed to fit a particular application are not totally compatible with the charging system controls. The alternator may bolt right in, but it fails to communicate with the PCM preventing it from charging normally.

Another item that can affect an alternator’s output is the pulley. Many late-model vehicles do not use a solid alternator pulley. Instead, they have an Overrunning Alternator Pulley (OAP) or an Overrunning Alternator Decoupler Pulley (OAD). An Overrunning Alternator Pulley (OAP) has a one-way clutch mechanism inside the hub that allows the belt to turn the alternator in one direction, but allows the alternator to free-wheel and spin at its own speed when the engine suddenly decelerates.

The pulley should lock up when it is turned one way, but freewheel when it is turned in the opposite direction. If the internal clutch mechanism is bad, the pulley may not drive the alternator, or it may remain locked all the time increasing noise and vibration. An Overrunning Alternator Decoupler (OAD) pulley also has a one-way overrunning clutch inside as well as an internal torsion spring to further dampen vibrations in the belt drive system. The spring acts like a shock absorber to cushion the hub.

This reduces noise at idle and low engine speeds, and helps dampen harmonic vibrations at higher speeds. If the clutch or spring inside the pulley has failed, the pulley may fail to drive the alternator, or it may create vibrations and noise. OAP and OAD pulleys usually thread onto the alternator shaft whereas solid pulleys are typically a straight slip or press fit with a large bolt on the end of the alternator shaft to hold them in place. Some replacement alternators come with pulleys and some do not.

If an alternator with an OAP or OAD pulley is being replaced, and the replacement unit does not come with a pulley already installed, the original pulley can be removed from the old alternator and installed on the new unit – provided it is in good condition. However, on high-mileage vehicles, replacing the original OAP or OAD pulley with a new one is recommended to assure trouble-free operation.

Symptoms

Water pump has missing or broken teeth, or sprocket falls off the shaft.

Probable Cause of Failure

Misalignment or damage of the tensioner, guide or chain.

Corrective Action

Visual inspection is required to verify the correct alignment of chain tensioner and guide. Inspect for broken, cracked or missing guide material as well. It is not advised to reuse misaligned components. Also, check the chain for any imperfections.

Correct alignment of tensioner and chain guide.

Incorrect alignment of tensioner and chain guide.

 If the chain looks like the circled areas, it is time to replace the timing components. Notice how the chain sags; this should not occur in any location of the chain drive. If slack is present, replace the chain, chain tensioner and chain guides.

In these circles, there is no slack present. This is the optimal position for the chain.

If serial data buses did not exist, a wiring harness would have to be five times its normal size and use twice as many sensors to deliver the same level of functionality and safety we see in the modern vehicle. For example, take a brake pedal sensor. On a modern vehicle, the position of the brake pedal is used by the shift interlock, ABS system, cruise control, traction control, brake lights and electric emergency brake. If each system required its own switch and wiring, the complexity of the wiring harness and switches would be a diagnostic nightmare.

Serial data buses also help to eliminate multiple sensors and wiring. One sensor can share information with multiple modules without having to connect directly to the multiple modules.

Serial data buses may seem like a daunting concept to some technicians, but understanding them is now a required skill to work on most modern vehicles.

What is On The Serial Data Bus?

A serial data bus uses voltage to communicate. Modules toggle the signal off and on, making the 1s and 0s of digital binary language like Morse code. This code can communicate commands that allow something as simple as rolling up a window or as complex as stability control correction.

Zero volts on any serial data bus is translated into binary language as “1,” and when the voltage increases the voltage to a specified level, it equals “0.” Most electronic devices operate on signals toggling between 0 and 5 volts. This includes laptops, DVD players and PCMs.

On most automotive serial data buses, the peak voltage level might be 7 volts. This extra voltage is to accommodate resistance in the wires and ground problems that may cause voltage drops. The extra 2 volts gives the network a safety buffer that may help the vehicle as it ages.

If a signal was on an equal length of time as it was off, you would have 0, 1, 0, 1, 0, 1 as the binary message being sent out. It could represent what the throttle position voltage is, a signal being sent from the airbag module to the BCM reporting the status of a sensor.

This could be a either a J1850 or CAN-Hi bus. Whatever the bus message, it’s comprised of 0s and 1s, or the states of highs and lows. Some systems use a variable pulse width that not only toggles between on/off, but can transmit additional information by varying the length of time the voltage is either on or off. This is how all serial data buses operate.

Binary Speed

What separates the earliest serial data bus from a modern CAN bus is how fast the system can toggle between 0 and 5 volts. The faster the switching, the more information can be transmitted in a given amount of time. Modern buses are able to do this with better software and with hardware that can interpret the signals with faster processors.

Faster speeds are needed so the ABS and PCM modules can communicate quickly if a stability control correction needs to be made that involves closing the throttle and applying the brakes.

Serial Data Bus Practical Diagnostics

You are never going to be able to look at the signals on a scope, decipher a series of 1s and 0s, and say that it is a command to turn on the brake light. What it can tell you is that a module is communicating and the bus is active.

But, the most critical skill for working on serial data buses is learning how to read the wiring diagrams to figure out how modules and sensors are structured on the bus.

In the auto repair world, the term used to describe the design, layout and behavior of a serial data bus configuration is “topology.”

Reading the Wiring Diagram

As a technician in the modern vehicle era, you’re going to need to understand these “bus lines.” The dotted line at the edge of the component, node or module indicates where the CAN bus enters and exits.

Some schematics may include other information in the boxes with two arrows pointing in opposite directions. All two-wire CAN bus lines terminate in a resistor(s) of a known value. This is what produces the correct amount of voltage drop.

Bus Configurations

There are three types of bus configurations that you will come in contact with — loop, star and a hybrid of both.

In a loop system, the topology of the nodes or modules is connected electrically in parallel.

Each node has two wires that connect it to the bus. This system multiplexes the nodes together so information can be shared along one circuit. With this system, all of the nodes can turn on a check engine light in the instrument cluster through the use of information within the circuit.

Each of these modules can communicate something to another module. For example, the HVAC would want to communicate with the BCM to ask permission of the PCM to turn on the compressor clutch by energizing the relay.

If you had an open circuit between the BCM and PCM, the PCM could still communicate to the BCM, although it would have to go through the other modules. Communication still takes place if you have one open circuit.

But, if you had two open circuits between the BCM and PCM, and an open circuit between the IPC and radio modules, the PCM would be isolated and would not be able to talk to the BCM or the ABS module.

Shorts in a Loop

The problem with a loop during diagnostics is if a short circuit occurs. The loop configuration can be easy to diagnose because even with two open circuits, nodes are isolated off the bus. But in a short circuit, with the modules in parallel, the whole circuit goes down.

When a bus shorts, it can be a difficult process to isolate the offending module or section of wiring. In a case where a module shorts out the bus, you would literally have to unplug them one at a time to see which module eliminates the short circuit. That would not be a good scenario in the repair world because it would take a lot of time to gain access to those modules.

Shorts are one disadvantage of the loop configuration. The advantage is you have a redundancy of wires. Therefore, these are more impervious to an open circuit issue.

Star Bus Configuration

The star configuration’s topology uses a comb, butt connector or shorting bar. It plugs into a female connector.

All of the modules have a single wire coming out of them on the serial data bus leading to that one common connector that would tie them all together in parallel.

The star configuration got its name from the computer industry. For example, an Ethernet connection is a star configuration with computers, printers and servers all connected to an Ethernet hub.

Star connectors are often located near the DLC, but note that there are exceptions. And, some manufacturers solder them in place while others don’t, allowing for the connector to be removed a lot easier. On some vehicles, the star connector can be removed and a meter can be connected to each circuit to test for shorts to power or shorts to ground.

Loop/Star Hybrid Versions

Automakers may also combine both loop and star topologies in a single-bus system.

They may wire them in a combination of both the star and the loop configuration where both systems have a number of nodes on them that talk on the loop and star.

If you know the theory on how this type of bus works, and there is a short to ground or power, the next step is to remove the splice packs and check the nodes.

If the short goes away, the next step is to unplug modules one at a time to see if that short comes back.

If the short is still present with the splice packs removed, it could be the nodes in the loop configuration. In this case, the ABS and instrument cluster modules might be a source of the short to ground or power, and are connected to the splice pack.

To eliminate them as the possible source of the problem, you’ll need to unplug and check these modules one by one.

Being able to recognize whether the topology is a loop, star or hybrid configuration will make testing and diagnosing shorts, grounds and communication errors faster and more effective than using steps and flow charts.

Knowing how both shorts to opens and normal shorts (power and ground) behave on a loop or star can help you formulate a more effective plan of action so you can do more in less time.

Bus Connection in the DLC

Since 1996, all vehicles sold have a diagnostic connector under the dash. Some pin assignments are standardized across all vehicles. Some pins assignments are left up to the manufacturer.

PIN 1: Manufacturer discretion. GM: J2411 GMLAN/SWC/Single-Wire CAN

PIN 2: Bus positive line of SAE-J1850 PWM and SAE-1850 VPW

PIN 3: Ford DCL(+) and Chrysler CCD (+)

PIN 6: CAN HI (ISO 15765-4 and SAE-J2284)

PIN 7: K line of ISO 9141-2 and 14230-4

PIN 10: Bus negative line of SAE-J1850 PWM only (not SAE-1850 VPW)

PIN 11: Ford DCL(-) Argentina, Brazil (pre OBD-II) 1997-2000, USA, Europe, etc. Chrysler CCD Bus(-)

PIN 14: CAN low (ISO 15765-4 and SAE-J2284)

PIN 15: L line of ISO 9141-2 and ISO 14230-4

Behind every kind of technical innovation that drives the automotive world into the future is a wealth of science and engineering that makes such innovation possible. The emergence of precious metal spark plugs is no different.

With the need to comply with ever-increasing efficiency and emission standards, auto manufacturers have been racing to raise the bar in spark plug performance over the past three decades. The use of precious metals like platinum and iridium in the manufacturing of spark plugs, as opposed to the use of nickel, has resulted in plugs that can last much longer and offer better performance than the spark plugs in circulation prior to the mid-1980s. Specifically, precious metals were introduced into the spark plug manufacturing process because their higher melting points: The melting point of iridium is 2450 °C, platinum is 1770 °C, and nickel is 1453 °C.

The higher melting point of iridium and platinum allows spark plug manufacturers to reduce the diameter of the center electrode. The smaller the diameter of the center electrode, the lower the voltage needed to start the spark. The finer point means that the electrode can absorb heat easier and faster, leading to improved acceleration, fuel consumption and smoother idling.

Copper Spark Plug Basics

Copper spark plugs have bodies made of copper with center electrodes comprised of nickel alloy. These plugs require more voltage to function than precious metal plugs. Because nickel alloy is softer than iridium and platinum, copper plugs wear out sooner than precious metal plugs. (Many have a recommended service interval around 30,000-50,000 miles). For this reason, copper plugs are best used in older vehicles with low-voltage, distributor-based ignition systems. It should be noted that while copper plugs are usually best for older vehicles, some newer vehicles with high-performance engines are designed for copper spark plugs. Always make sure to consult the owner’s manual if there is a question as to which type of spark plug replacement is recommended.

Platinum Spark Plug Basics

Platinum spark plugs were introduced in the mid-1980s and quickly gained favor for their heat-resistant and wear-resistant properties that allowed them to last upwards of 100,000 miles in some instances without needing replacement. Platinum plugs run hotter than copper plugs. This helps reduce deposits and prevent fouling. While these plugs offer high performance and a longer lifespan, they do come at a cost. Typically, platinum spark plugs cost two to four times that of traditional plugs, but can make up the cost differential with their longevity. Use these plugs with newer cars with electronic, distributor-based ignition systems. Some distributor-less systems require these plugs as well.

Iridium Spark Plug Basics

Iridium spark plugs entered the market in the mid-1990s. Because iridium is one of the world’s hardest metals, it is very resistant to spark erosion. On these spark plugs, Iridium’s properties reduce the ignition voltage requirement considerably and contribute to improving the spread of the flame front in the combustion chamber. The service life of iridium plugs is double that of standard plugs, and can be up to 25 percent longer than that of platinum plugs.

Double Platinum/Double Iridium Spark Plugs

Double platinum and double iridium spark plugs were developed for use in waste spark distributor-less ignition systems. In these applications, both the center electrode and side electrode feature precious metal discs that allow sparks to move in both directions without prompting excessive electrode wear. On the compression stroke in vehicles with these types of spark plugs, the spark shoots from the center electrode to the side electrode. Conversely, on the partner cylinder exhaust stroke, the spark shoots from the side electrode to the center electrode.

Replacement Intervals

Factory-recommended spark plug replacement intervals have consistently been in the 100,000-120,000-mile range in recent years thanks to the efficiency of precious metal plugs, but these spark plugs can still continue performing well long after these intervals have been reached. However, it is important to keep an eye on spark plug performance as they approach 100,000 miles of use. As electrodes wear over time, spark plugs require more voltage to fire. If this wear goes undetected, this strain can cause misfires.

Misfires need to be promptly addressed, as they lead to a loss of power and fuel economy. What often goes unnoticed, though, is that misfires also lead to an increase in unburned hydrocarbon emissions. When this goes undetected, the catalytic converter can become overheated due to the excess of hydrocarbon it has to process. Overheating is a major cause of catalytic converter damage, and often necessitates catalytic converter replacement when not taken care of.

Installation Best Practices

Always make sure that when replacing spark plugs, you use parts with the same thread diameter, pitch and length as specified by the manufacturer.

According to the NGK Technical Support Team, “Technicians should keep in mind that most of the newer model vehicles come out of the factory with precious metal plugs, and they should be replaced with the OEM-style plugs. Installing alternate plugs might cause loss of fuel economy and performance.

“Also, there is a myth that the fine-wire precious metal plugs should not be gapped. That is a false statement. You should always double-check the gap using a wire-style gapping tool. We do not recommend using the ‘coin’ style gapping tool because it can damage the fine wire tip.”
Change comes quick in today’s automotive aftermarket. And while the size and shape of spark plugs might condense in the future to better fit shrinking engine compartments, the use of precious metal spark plugs is something that is expected to continue into the foreseeable future.

“I think the material choices are going to remain fairly stable,” Champion Product Manager Michael Kollenberg said. “Not that we’ve reached the pinnacle, but between iridium and platinum materials and the way they are alloyed with different metals, I think we’re really at the top of our game with respect to what materials function in those environments the best and last the longest. Unless there is a major shift to some new and significant raw metal material, I can’t see the iridium or platinum plugs going away any time soon.”

Power windows are a great convenience, but sometimes they stop working. Sometimes the fault is electrical, such as a bad power window switch, a blown fuse, a bad relay or a loose or damaged wire. Other times, the fault is a bad window motor or a broken part in the window regulator mechanism that actually raises and lowers the glass.

Single-Lift Drum and Cable Window Regulator

The window lift components inside the door usually include a small electric motor and a window regulator assembly. The motor and regulator can be replaced separately most of the time, though both require removing the inner door panel to replace the parts. Replacement typically takes an hour or so, but may require an extra set of hands to hold the glass while parts are aligned and maneuvered into place.

The electric motors that drive power windows are compact and powerful and are similar to the motors used on power seats. OEM motors can cost anywhere from $100 up to $300 or more depending on the application.

On some vehicles, the window motor brushes can develop dead spots after four or five years of service due to lowering and raising the windows every time the door is opened. It makes for a tight seal, but all the extra motion also shortens the life of the window motor.

Double-Lift Window Regulator

The regulator assembly that raises the window is mechanical, and it is subject to wear over time whether it is power driven with a motor or is manual with a crank. Window tinting on some vehicles can cause extra stress on the motor and possibly cause stress on the regulator.

Some regulators use a steel cable and worm-drive gears to lift the window, while others use a notched plastic belt or plastic strip with teeth for the same purpose. Steel cables seldom fail, but plastic belts and strips often become brittle with age and exposure to heat. This leads to cracks and part failure, especially during cold weather.

On some applications, the plastic belt or strip can be replaced separately without having to replace the whole regulator mechanism.

The plastic bushings and slides in the window lift mechanism may also be subject to wear, causing misalignment or sticking when the window goes up and down. This can result in a poor glass seal with wind noise and/or water leaks.

The regulator assembly is usually bolted inside the door frame and attaches to the bottom of the glass. Regulators can be relatively simple and compact or large and complex. OEM replacement regulators (if available) may cost $150 up to $600 or more depending on the vehicle.

For applications that are more than 10 years old, OEM parts may no longer be available. Fortunately, there are aftermarket repair parts available for many applications.

Related items a customer might need when replacing window lift components include new weather-stripping for the door and weather-stripping adhesive or sealer to repair loose or leaky seals.

Most shops in colder climates start to see an influx of customers with battery service needs as the temperatures drop. Perhaps more than any other maintenance category, being proactive about taking care of your customers with dying or dead batteries is essential this time of year.

Lead-acid batteries have an average service life of roughly three to five years depending on the climate. While Absorbent Glass Mat (AGM) gel cell batteries typically last a few years longer, both are prone to failure as the temperature dips. The only way to spot a weak battery is by testing it. If your test shows it’s time to replace the battery, be sure to follow recognized replacement best practices.
 

Winter Battery Service Tips

• Be Careful Handling the Battery: Lead-acid batteries containing liquid electrolytes can spill if not handled properly. The acid in this liquid can be caustic to the skin and burn through clothing. If handling such a battery, consider using a carrying strap that attaches to the battery posts or the strap on the battery case (if it has one). At the very least, lift the battery carefully from underneath and be sure not to squeeze the sides of the case since acid can leak out the top when under pressure.

• Steer Clear of Frozen Batteries: Batteries can freeze when the vehicle has been sitting in extreme cold. Never try to jump-start or recharge a battery that is frozen since it is more prone to exploding. You can try to remove the battery from the vehicle and let it thaw before charging or testing, but most batteries that have been frozen will require replacement.

• Protect Yourself From Shock Hazards: Most batteries only produce 12 volts, so there is no danger of being shocked by the battery, charger or jumper cables. The one exception is high-voltage hybrid batteries, which pack as much as 300 volts and are capable of delivering a lethal shock. On hybrid vehicles, don’t touch any of the hybrid electrical components without first isolating (disconnecting) the hybrid battery. Most have a safety switch that disconnects the battery from the rest of the electrical system. Refer to the owner’s manual or the OEM service procedures for how to do this as procedure.
   
  Important: Wear gloves rated to withstand 1,000 volts and don’t touch any orange color-coded cables until the high voltage battery has been disconnected when servicing these vehicles.

A Couple Notes on Battery Charging

• Do not turn the charger on until both leads have been connected to the battery. Connect positive to positive and negative to negative. Do not reverse the connections, as doing so may damage the charger and battery.

• Slow-charging at 6 amps or less is best because it develops less heat inside the battery (which can damage cells and increase evaporation). A slow charging rate will also break up the sulfation on the battery plates more efficiently to bring the battery back up to full charge.

• “Smart chargers” also work well because they automatically adjust the charge rate to the battery’s state of charge. Most start out with a charging rate of 15 amps or higher, then taper off the charging rate as the battery charge increases.

• Fast-charging a battery saves time, but risks overheating and damaging the battery. If using a fast-charger, don’t use the highest setting. Use the “boost” setting only when cranking the engine.

• Refer to the battery’s reserve capacity (RC) rating to determine charging times and rates. The charging rate (in amps) multiplied by the number of hours of charging time should equal the reserve capacity of the battery. (Example: a dead battery with a RC rating of 72 will require charging at 6 amps for 12 hours.

The concept of using a torque converter, oil pump, planetary gear sets, clutches, bands and a computer-controlled hydraulic valve body to transmit torque and to change gear ratios is relatively simple. The torque converter allows the engine to idle in gear with the vehicle stopped and multiplies engine torque during the initial stages of acceleration. In addition to an electronically controlled clutch that prevents the torque converter from slipping during cruise conditions, the primary parts of the torque converter are the impellor, stator and turbine.

Each of these parts has a set of curved vanes that accelerates and controls the flow of oil in the torque converter housing. The impellor, which is driven by the engine, uses centrifugal force to push oil into the turbine. The turbine, which is attached to the transmission input shaft, receives the impact of the rapidly moving oil to develop a torque input to the vehicle’s drivetrain.

The difference between the speeds of the impellor and turbine is called stall speed. Generally, stall speed is limited to 1,500-2,000 rpm to prevent overheating the transmission oil. Torque converter hydraulic “lock-up” occurs when oil velocity in the converter is high enough to keep the impellor and turbine rotating at nearly the same speed.

The stator, which is attached to the transmission front oil pump assembly, contains a one-way roller clutch assembly that locks the stator in place during acceleration and allows it to freewheel during deceleration. During acceleration, the impellor is rotating faster than the turbine. The stator redirects oil from the turbine into the faster-rotating impellor blades to multiply torque. During deceleration, the direction of oil flow in the converter reverses because the turbine becomes the driving component. The stator must then freewheel to allow the oil to reverse its direction of flow.

he most labor-intensive seal to replace on any engine is the rear main seal. There are no shortcuts or quick fixes if the seal has expired. On most modern engines, the seal’s failure is due to a condition inside the engine or a component connected to the back of the engine.

Solving why the seal failed in the first place is critical to preventing a labor-intensive comeback. Here are six questions you should be asking yourself before, during and after a rear main seal job.

Is it the rear main seal that is leaking?

It might not be. On most engines, oil leaks can occur above and below the rear main seal. It could be a leaking oil pressure sensor, oil pan gasket or galley plug near the seal that causes oil to come from the bell housing. Adding dye to the oil can help reveal where the oil is coming from.

Is the PCV system clogged or blocked?

Most rear main seals have a lip that rides on the shaft. The pressure inside the crankcase will push the lip onto the shaft. Too much pressure will eventually cause the lip to balloon and allow oil to pass. If the Positive Crankcase Ventilation (PCV) system is blocked, it will increase the pressures inside the crankshaft and push out the seal. Also, if the engine is supercharged or turbocharged, excessive blowby due to worn or damaged piston rings can cause increased crankcase pressure that can also damage the rear main seal.

What is the condition of the oil?

Most oils have chemicals in their additive packages that will condition the seals in the engine. If the oil is not changed regularly, it will cause the seal to degrade. The seal conditions are depleted over time along with buffers in the oil. The lip that rides on the crankshaft will become stiff and will not be able to seal itself against the crankshaft.

What is the condition of the crankshaft?

The condition of the surfaces that the rear main seal rides on is critical. Any imperfections or wear on the crankshaft can cause a leak. There are sleeve kits that can be installed on the crankshaft to restore the surface.

Did you follow the directions that came with the seal?

Some rear main seals need to be installed dry. These seals have a polytetrafluoroethylene (PTFE) coating on the lip seal that needs to be dry and seat to a dry surface on the crankshaft. The seal will transfer a layer of PTFE to the crankshaft surfaces that the lip will ride on. The transfer layer prevents wear while sealing better than a silicone or Viton material. If the seal is installed with a coating of oil, it will start to leak in a few miles.

Are there alignment issues?

If there are any alignment problems with the bell housing or input shaft of the transmission, they can cause stress on the rear main seal. Make sure you check the input shaft on a manual transmission for play. On vehicles with automatic transmissions, check the flex plate for lateral runout or damage.