2004 Cadillac DeVille 4.6L V8

This customer had been to the dealer for some random electrical problems. He decided not to have the dealer work on his car after a long conversation with the service writer. He called me to come out and look at his vehicle.  I did some basic diagnostics and found a few DTC’s in 6 modules. Most were communication problems on the Class 2 data buss. I did some voltage drop tests and found the electrical system had a 900 MV voltage drop on the ground side. After some circuit integrity work the voltage drop was brought down to 52MV.  100 MV is the expected limit on the main 12 volt power system. This resolved the abnormal electrical issues and the customer was very happy with the results. The dealer wanted to charge over $200 dollars to just look at it and claimed it might need a PCM.  More guesswork without knowing what is really happening. I also found the vehicle had an HVAC system code and the customer wasn’t sure if he wanted to fix it. After fixing his random electrical issues, he decided to have me fix the HVAC system fault also. The system had a DTC B0429. The IPM stored this DTC from the HVAC module and the controller couldn’t store a proper actuator module calibration. After some diagnostics, I found the actuator was not able to control the 3rd door for the rear A/C controller. This system has auto climate control with 3 zones. Drivers, passengers and rear seat. It was necessary to replace the temperature door actuator module and calibrate it to the system.  After all this electrical diagnosis and repair, the customer requested me to do a complete tune-up.  Happy customers are always the best customers. Don’t let guesswork diagnosis cost you unnecessarily.

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