Deceptive Diagnosis

DECEPTIVE DIAGNOSIS

Disclaimer of Warranties:

This manual contains test procedures and test information obtained by an ASE Master Technician with known good test equipment on real vehicles. Your tests may vary due to your test equipment or procedures. No warranty can be made from the ideas presented due to personal testing procedures, nor does the author or anyone connected with him or her assume any responsibilities or liabilities. The use of this manual is conditional on the acceptance of this disclaimer. If the terms of this disclaimer are not acceptable, please return this manual.

Automotive Video 6280 Arc Way Ft. Myers, FL 33966 1-800-71-TRAIN (1-800-718-7246) www.auto-video.com `çåíÉåí ~ìíÜçêÉÇ Ñçê ^ìíçãçíáîÉ sáÇÉç Äó eÉêáí~ÖÉ qÉÅÜåáÅ~ä ii`I `çÅÜê~åîáääÉI m^K `çéóêáÖÜíÉÇ « áå OMNP Äó ^ìíçãçíáîÉ sáÇÉçK kç éçêíáçå çÑ íÜáë ã~åì~ä ã~ó ÄÉ ÅçéáÉÇI ~äíÉêÉÇI çê êÉéêçÇìÅÉÇ ïáíÜçìí ïêáííÉå éÉêãáëëáçå çÑ íÜÉ ~ìíÜçêK

41202 DECEPTIVE DIAGNOSIS

DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

TABLE OF CONTENTS

INTRODUCTION ...... 2 CASE STUDY 2: 2010 CHEVROLET AVEO ...... 8 INFORMATION SOURCES ...... 2 CASE STUDY 3: 2008 CHEVROLET SILVERADO ...... 10 CASE STUDY 1: 2005 DODGE MAGNUM WAGON CASE STUDY 4: 2007 CHEVROLET AVALANCHE ...... 12 5.7L HEMI ...... 5 IN CONCLUSION ...... 24

1 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

INTRODUCTION

During this presentation we will be looking at four interesting case studies and discuss the fact that sometimes the books and charts do not lead you down the correct diagnostic path. This course will hammer home the fact that sometimes it is more important what the books don’t tell us than what they do tell us.

We will also be covering where to get information that goes beyond what we normally use such as Alldata, Motor and Mitchell as well as the OEM service websites.

All of this combined with the case studies should give a great example on how to diagnose problem vehicles “outside of the box” and help you eliminate deceptive diagnosis problems on vehicles that show up in your service bay.

INFORMATION SOURCES

As you know, there are a variety of technical information sources that we as technicians can draw knowledge from. The question that really needs to be answered is can we really have too much technical information? Obviously, the answer is absolutely not. The list of aftermarket repair information can include Motologic, Alldata, Motor, Identifix and the list goes on. One thing these sites and the others as well, have in common is the vast amount of valid diagnostic and repair information.

Other websites such as the International Automotive Technicians Network (iATN) are mainly focused around groups of technicians banded together to help one another solve automotive technical problems.

Lastly are the less conventional sources of automotive information such as YouTube Linked In and vehicle specialty forums such as nationalcorvetteowners.com where they specialize in the Chevrolet Corvette.

Even with all of these sources of information available the best source still remains the OEM information. For the most part, aftermarket websites are harvesting the information from the OEM websites and offering it together with other information from other manufacturers at a reduced cost. One of the advantages of this concept is the user will get multiple makes and models for a large amount of year coverage at a low cost. The main disadvantage is the timeliness of the information. OEM websites have the latest and greatest information available at any given time.

2 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

INFORMATION SOURCES

The best place to access the OEM information from the internet is http://oem1stop.com/. This site has links to all of the major manufacturers and the navigation could not be easier. As you can see in the illustration above, we have chosen Chevrolet from the main menu and a sub menu pops up giving us the ability to choose Mechanical, Collision or Hybrid & Electric information.

Tech Tip! If you have spent more than four hours diagnosing a problem vehicle using the aftermarket information, do yourself a favor and subscribe to the OEM information. The OEM source of information is more up to date and accurate and will save you time if you become mired in a vehicle you cannot figure out a hard to diagnose problem on the vehicle you are working on.

Even with the OEM information being the best you can get, there will still be errors and omissions within the vehicle information. This information will then disseminate down to the aftermarket information and be wrong within their product as well. The reasons for these errors vary due to human error and computer and systems errors as well.

A prime example of this is a 2008 Chevrolet Malibu with an A/C odor problem. The problem stems from moisture on the A/C evaporator core that does not dry. This causes a mold to grow on the evaporator and an odor to be ventilated into the passenger area of the car. There are several ways to combat this problem such as coating the evaporator with a substance that won’t allow mold to grow but there is also a process that can be enabled within the vehicles body control module called Afterblow.

3 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

INFORMATION SOURCES

The interesting point about this process is that within the service information, it is described vastly different as illustrated in the example below.

EXAMPLE 1: The afterblow function is not enabled from the factory. To enable this function the following must occur. As soon as the ignition is turned off, and all active process is complete, the controller is put into low power mode. A high voltage wakeup is generated on the low speed GMLAN by the BCM and the HVAC virtual network is activated. Embedded in the GMLAN message is afterblow control logic bit (Aftrblw_active).

The above example is nice if you want to know how the system works from a description and operation standpoint but doesn’t really tell us HOW to make it happen. Nowhere do we see any type of procedure or even the word scan tool.

Within the HVAC section of the service manual we see something totally different as illustrated by example 2 listed below

Example2: Afterblow is a feature that dries the evaporator core by operating the blower motor after the engine is turned off. This reduces the amount of microbial growth that can create undesirable odors. The vehicle does not come equipped with the afterblow feature turned on. If the afterblow feature is required due to an odor concern, it must be turned on by using the scan tool. This enable option of this feature can be found in the body control module.

4 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

CASE STUDY 1: 2005 DODGE MAGNUM WAGON 5.7L HEMI

Our first case study involves a 2005 Dodge Magnum with a 5.7L Hemi engine. The original customer complaint when the vehicle arrived at the service center was it had a severe misfire. Upon further inspection the technician found there were misfires on cylinders 1 & 7 and DTCs P0300, P0301 & P0307 were present.

As any good technician would do, the technician performed a compression test. The compression test revealed there was NO compression on the two cylinders with the misfire problem. Without performing a cylinder leak down test, the technician concludes there must be a leaking cylinder head gasket causing the fault. To confirm this diagnosis the technician used a piece of diagnostic equipment that detected carbon monoxide within the radiator and cooling system.

The technician removes the cylinder head, cleans the surfaces, replaces the cylinder head gasket and replaces the cylinder head. Once the repair has been completed the technician attempts to verify the repair but finds the original problem of the misfire was still present. The technician then removes the valve cover and cranks the engine and observes the rocker arms on cylinders 1 and 7 are not functioning.

When the technician dug a little bit further into the problem using the OEM service information he found the vehicle he was working on was equipped with a Multi Displacement System (MDS). Chrysler's Multi- Displacement System (MDS) is an automobile engine variable displacement technology. It debuted in 2004 on the 5.7 L modern Hemi V8. Like Mercedes-Benz's Active Cylinder Control, General Motors' Active Fuel Management, and Honda's Variable Cylinder Management, it deactivates four of the V8's cylinders when the throttle is closed or at steady speeds.

The 5.7L HEMI system utilizes a latching lifter, such that when the control system signals for a cylinder to become deactivated a solenoid opens and sends high pressure engine oil through a control gallery in the block that acts on a pin in the lifter to "un-latch" the lifter. Also packaged inside this special lifter is an extra spring called a lost motion spring, it's purpose is to keep the roller part of the lifter in contact with the cam and the push rod in place in the rocker arm.

A common failure of these systems is if the oil is not changed regularly, the oil control solenoids can become loaded with sludge or even break the screens. The technician changed the engine oil and filter and replaces all four control solenoids. Unfortunately, this did not fix the problem either. We now have the MDS system working fine but the original complaint of a severe misfire is still present.

After a lengthy test drive with the vehicle connected to a lab scope, the technician found the high side drivers controlling the MDS were staying intermittently ON when they should have been off. This malfunction caused cylinders 1 & 7 to be disabled when they should have been working correctly. This fault caused the PCM to report cylinders 1 & 7 misfiring which was the customer’s original complaint.

At this point the technician knows what the problem is but has no idea on what is causing it. It could be a bad transistor or faulty wiring or even a break in the wiring. The technician decided the best course of action was to cut the wire to the solenoid making sure it was not shorted to power. After cutting the wire, the technician made the determination that the PCM was at fault and replaced it.

Once the PCM was replaced he realized he had to reflash the PCM with the correct calibrations. He also realized since this was a CAN BUS equipped vehicle, the vehicle would have to “Relearn” certain things such as the Sentry Key Immobilizer Module (SKIM) antitheft system. Not only will the vehicle need the SKIM relearn, it will also need a throttle relearn.

5 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

CASE STUDY 1: 2005 DODGE MAGNUM WAGON 5.7L HEMI

LOW SIDE DRIVERS

HIGH SIDE DRIVERS

6 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

CASE STUDY 1: 2005 DODGE MAGNUM WAGON 5.7L HEMI

One other problem facing the technician at this point (as if he doesn’t have enough problems with this vehicle), he will be able to reflash the PCM for all of the items related to powertrain management such as throttle relearn with an aftermarket scan tool. For items such as the SKIM, he will need to use a factory scan tool as it is the only tool capable of reprogramming the BCM for this vehicle. Unlike Ford, GM and many other manufacturers you can reprogram any module using an aftermarket scan tool and a J2534 pass thru device, Chrysler requires you to use the factory scan tool.

Even though we have not programmed the SKIM code into the vehicle, the vehicle still starts and runs without illuminating the MIL but DTCs (P0633 & P1697) are stored in memory as expected. As we discussed earlier, the aftermarket scan tool would not allow us to reprogram the SKIM codes into the PCM but it would also not allow us to reprogram the vehicle mileage into the PCM only the factory scan tool would allow us to do it.

Once the SKIM codes were entered and the mileage reprogrammed using the factory scan tool, the problem was solved. The last thing we needed to do was to make sure a successful drive cycle was run and all of the monitors were set to ready.

The moral to this story is to know what advanced systems the vehicle you are working is equipped with and never give up. This seemed to be a simple misfire problem but was caused by multiple faults. This was a big job with many technicians involved as well as advanced diagnostic equipment including the factory scan tool.

7 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

CASE STUDY 2: 2010 CHEVROLET AVEO

Our next case study vehicle is a 2010 Chevrolet Aveo with a customer complaint was the car had been severely overheated. The first shop that worked on the vehicle thought a simple head gasket replacement would fix the vehicle. Once they removed the cylinder head they found the cylinder head was cracked. This shop did not have the time to work on the vehicle so they sublet the repair to another shop.

The next shop took delivery of the vehicle from a tow truck with the cylinder head and other related parts in the trunk. The second shop chose to replace the entire engine with a known good engine from a reputable salvage yard. Upon further inspection of the salvage yard engine the technician observed there was damage to the throttle body. Since there was no damage to the throttle body on the original engine, the technician swapped them out and continued the repair.

Once the repair was complete the technician started the vehicle and found the engine would only respond to the first wide open throttle (WOT) snap, set several DTCs, then have no throttle response whatsoever. After the DTCs set, the engine no longer had electronic throttle control response.

All of the DTCs were manufacturer specific. DTC P2105 TAC system forced engine shutdown was intermittent and only set part of the time. DTC P2106 throttle control system performance: throttle limitation active was obvious because when we pressed the accelerator pedal nothing would happen. DTC P2110 TAC system forced limited engine speed was enough for the engine to have limp in mode. Finally, DTC P161B control module torque performance is another engine performance issue. All of the DTCs certainly fit the profile of a problem of communication between the accelerator pedal and the throttle body in a vehicle equipped with a throttle by wire system.

The technician immediately thought there was something he missed in a step or two when replacing the engine. Could it be he left a sensor unplugged? Could it be he damaged a component or wire during the repair? Or could it be a problem with the PCM that was there before the engine was replaced?

After further inspection we noticed when the engine is running at idle after setting the DTCs, there is a power surge within the engine that occurs exactly every 30 seconds. This speed up and slow down of the engine was very systematic and on time like clockwork. A logical conclusion to this would be a computer causing the fault. The only things that can happen like clockwork are things that use a clock to function such as a computer. For whatever reason, every 30 seconds, the PCM commanded the engine rpm to increase (surge), then return to idle.

As we reviewed the scan tool PID data we notice the engine load percentage showed 100% while the vehicle was at idle. A normal 4 cylinder engine might have as high as 45% engine load at idle but not 100%.

8 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

CASE STUDY 2: 2010 CHEVROLET AVEO

At this point we went back to basic diagnostics and began unplugging the vehicles sensors and actuators to see if it made a difference in the engine performance. Why do we do this? We do this to see if the PCM will return a default signal to the engine if it does not see an accurate reading from the sensor we unplugged. If the engine runs better with the default signal than the signal from the sensor, we know we have at the very least localized in what is causing the fault.

As we moved from sensor to sensor we found the hose to the MAP sensor was rotted and broken. This is a classic example of a vacuum leak. What was the PCM seeing when the engine was running? Due to the vacuum leak it thought the throttle was pressed to the floor but is not correlating with the corresponding TPS voltage. This will cause the PCM to determine that the throttle is out of control resulting in no electronic throttle control commands being allowed. The PCM will only allow limited throttle response and rpm just enough for limp in mode.

The lesson learned from this case study: no matter how high tech the problem looks, do not overlook the basics.

NOTES

9 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

CASE STUDY 3: 2008 CHEVROLET SILVERADO

This next case study involves a 2008 Chevrolet Silverado where both of the vehicles key fobs are inoperative. The fleet operations service technician tested the key fobs at a local parts store and determined the fobs to be fine and has diagnosed the problem as a faulty Remote Keyless Entry (RKE) module.

Once the technician determines the problem to be the RKE module, he orders one from the dealer and replaces the defective module with the new one. After the replacement of the module the technician successfully performs the key fob learn procedure and returns the vehicle to active service.

Once the vehicle is returned to service, a new problem arises. We now have a TPMS warning message on the instrument panel where there was none prior to the repair. What is the connection between these two systems? Both of these systems work off of radio frequency (RF) and both of these systems work on the same module within the vehicle.

When the RKE module was replaced, it no longer recognized the signals being transmitted from the vehicles tire pressure sensors located within the wheel and tire assembly of the vehicle. The module knew the signal from the sensors should be there but did not recognize the signal being sent. Getting the RKE module to recognize the TPMS signal required a reflash of the RKE module that was replaced. Once the RKE module was reflashed, the key fobs work correctly and the TPMS signal is now recognized by the RKE module.

We thought this was the end of our problems but it was not. We now had a new problem? The new problem is the odometer has switched from reading miles to kilometers. After researching the vehicles owner’s manual and service manual we found no way of switching the reading back to miles. The next step was to search the GM TIS 2 Web and the SI 2000 for any and all TSBs that may be related to this problem. We still found nothing to help solve this problem.

At this point we are led to believe that we have done something during the repairs to cause this problem. One final thing we want to do before we start swapping out parts on the vehicle is to search the TIS 2 Web site to see if there are ANY calibrations related to the instrument cluster that might solve this problem for us.

10 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs

CASE STUDY 3: 2008 CHEVROLET SILVERADO

What we found did not help us one bit. It appears that we already have the latest calibration for the instrument cluster installed on the vehicle. Normally, you do not reflash any component on a vehicle with the same software calibration that is already installed on it. In fact, Ford Motor Company will not let you reflash a component with the same software calibration and neither will Toyota. Chrysler and GM are exceptions to this rule however.

From experience, we know that sometimes bits of data on a computer can become corrupt. Think about it, how many times have you had to reinstall a piece of software on your computer at home because of a virus, malware or a power surge? The computers on cars and trucks are no different. They can (and will) from time to time become corrupt with data or lose data all together.

At this point we had nothing to lose by reflashing the instrument cluster with the same software calibration that was already installed on it. We reflashed the instrument cluster that had somehow been affected by the reflashing of the RKE module, and it worked perfectly. We don’t know why the calibration became corrupted but it did and reflashing the cluster with the same calibration that was already stored within the component fixed the problem.

What is the lesson to be learned with this case study? When in doubt, reflash if you can. However, if there is no reason to flash a vehicle module, don’t do it.

NOTES

11 DECEPTIVE DIAGNOSIS Presented by Dave Hobbs