DTC U0001 Set Current or History - keywords code communication ECM engine lamp light PCM service SES

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

DTC U0001 set as a current or history code. There is no service information on this DTC. The U0001 will set when there is an open, short to ground or voltage on the high speed LAN communications data line.

Follow eSI Document ID # 1486714 Scan Tool Does Not Communicate with High Speed GMLAN Device.

Note: For the 2005 SSR there is a PCM calibration in TIS for "New Software With Diagnostic Enhancements For DTC U0001". This calibration will NOT eliminate the code. This calibration only changes the criteria for the code to set.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.