MolaKule
Staff member
This past winter we had numerous intermittent StabiliTrack codes. Sometimes the steering wheel position sensor or wheel speed sensors and connectors can get flaky and throw these codes, but no fault was found with these.
GM had issued a TSB for this problem and reprogramming, but none of these codes made any sense.
The wife came hone Saturday after her trip to her mom's and said the '08 TrailBlazer had no AC, no PWR Windows, no guages, no radio.
I checked all of the pertinent fuses in both the Engine Compartment and those underneath the back seat and no blown fuses.
I hooked up my OBD-II scanner and no talky to the PCM, no codes.
I was fearing an Instrument Cluster and or CAN bus problem.
I unhooked the various Control Modules one-by-one.
It turned out that the OnStar module was partially shorting the CAN bus and pulling down voltages from the PCM.
Disconnected the OnStar module and wolla, everything worked again. Since we don't use it and never did, I did not replace it with a new $600.00 unit.
The CAN bus is great when you have various control modules scattered around the vehicle, but it only takes one module with a flaky CAN transceiver or cable fault to bring it down. When this happens, the PCM goes into its Default/Open-Loop mode so one can still drive the vehicle home or to the repair shop.
GM had issued a TSB for this problem and reprogramming, but none of these codes made any sense.
The wife came hone Saturday after her trip to her mom's and said the '08 TrailBlazer had no AC, no PWR Windows, no guages, no radio.
I checked all of the pertinent fuses in both the Engine Compartment and those underneath the back seat and no blown fuses.
I hooked up my OBD-II scanner and no talky to the PCM, no codes.
I was fearing an Instrument Cluster and or CAN bus problem.
I unhooked the various Control Modules one-by-one.
It turned out that the OnStar module was partially shorting the CAN bus and pulling down voltages from the PCM.
Disconnected the OnStar module and wolla, everything worked again. Since we don't use it and never did, I did not replace it with a new $600.00 unit.
The CAN bus is great when you have various control modules scattered around the vehicle, but it only takes one module with a flaky CAN transceiver or cable fault to bring it down. When this happens, the PCM goes into its Default/Open-Loop mode so one can still drive the vehicle home or to the repair shop.
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