Traction Control Light – the traction control light (TCS) and anti-lock brake systems (ABS) lights are illuminating.
The subject vehicle for this week’s article is a 2004 Cadillac Escalade ESV with a 6.0 Liter (366.15 C.I.D.), automatic transmission, and 58,995 miles (94,943 KM) on the vehicle odometer. The customer complaint is the traction control light (TCS) and anti-lock brake systems (ABS) lights are illuminating. The vehicle was given to a trainee who had just been hired. The trainee decided to install a scan tool for the test drive. The trainee connected the scan tool to the on-board diagnostic connector (OBDII connector) to perform a Key-On-Engine-Off (KOEO) test to scan for codes. The scan tool would not communicate with the vehicle. The trainee then, verified that the scan tool had been programmed correctly for the vehicle he is working on. The trainee verified the scan tool was programmed correctly; the trainee decided it must be the scan tool malfunctioning. The trainee decided to use a different scan tool to see if it would communicate with the vehicle. The second scan tool would not communicate with the vehicle; the trainee verified he had programmed the scan tool correctly. The scan tool was programmed correctly for the vehicle and this scan tool would not communicate with the vehicle on-board diagnostic system ether. The trainee decided to test drive the vehicle without a scan tool monitoring the suspected systems. The traction control and anti-lock brake systems warning lights were illuminating during the test drive. The trainee then proceeded to perform a visual inspection of the ABS system and TCS system components. The trainee found no damaged wires or components. The trainee then decided to check the wheel speed sensors with his meter. After checking the wheel speed sensors and finding them to be within manufacturers’ specifications the trainee ask his mentor for help. The mentor asks the trainee if he had retrieved any codes for the vehicle. The trainee replied that he could not get ether of the shops scan tools to communicate with the vehicle. The mentor then asked if he checked for any Technical Service Bulletins (TSBs) that matched the customer complaint. The trainee answered “no”. The mentor instructed the trainee to look up TSBs and then get one of the shop scan tools and he would assist him at the vehicle. There were no technical service bulletins that matched the customer complaint. The mentor joined the trainee at the vehicle and assisted the trainee in connecting the scan tool. The scan tool would not communicate. The mentor pointed out to the trainee that the scan tool was operating on its battery and not being powered by the vehicle. The mentor then had the trainee test PIN 16 on the OBDII connector for power. There was no power at PIN 16. The trainee looked up the wiring schematic that showed how PIN 16 gets power on this vehicle. A quick check of the cigarette lighter fuse which was the circuit protection was found to be faulty (blown). A new fuse was installed. The scan tool was connected and this time the tool communicated with the OBDII diagnostic system. A diagnostic trouble code (DTC) C0455 Front Steering Position Sensor Circuit was retrieved from the vehicle. The trainee then look up the details of the diagnostic trouble code and found that this fault could be set if the vehicle had an alignment recently and the system was not properly relearned to the alignment. The shop record showed no alignments had been done at their shop. The mentor then contacted the customer and asked if he had an alignment done. The customer stated he did have an alignment done a few weeks ago. The mentor then asked when the lights started illuminating. The customer stated shortly after the alignment. The mentor then request authorization to perform a relearn of the electronic steering system from the customer. The customer authorized the procedure. The trainee and mentor worked together and followed the manufacturers’ procedures for relearning the system. The trainee reexamined the customer complaint and based on what he had found and repaired concluded that he should have asked for assistance when the scan tool did not communicate with the vehicle. The vehicle was driven to verify the repair. Both the TCS and ABS lights no longer illuminated. Conclusion: The trainee should have asked for assistance when the scan tool failed to communicate with the vehicle. This would have saved a lot of time. Performing test in the “blind” on a system that you think is causing the system warning light to illuminate is not a good practice. Resolving the scan tool communication problem allowed for the retrieval of the diagnostic codes which lead to a proper repair! The trainee now knows that an improperly done wheel alignment can cause TCS and ABS warning lights to illuminate.