This bulletin applies to 2011 Cadillac DTS models. Some customers may complain about door locks cycling while driving, an intermittent no-start, a Service Stabilitrak DIC message and the speedometer and tachometer freezing while driving.
Along with these complaints, DTC U0140 00 and/or U0073 71 may be stored as a history code in any GMLAN High Speed module.
If the data circuits (2500 and 2501) have experienced an intermittent short to ground or short to each other two times within a period of less than 1 second and then go back to normal, the BCM may appear to be off-line on the high speed bus. This intermittent scenario should not cause other modules to lose communication.
If this happens, the BCM will not start communicating with other modules again until the key is out of the ignition ands the BCM has timed out (about 20 minutes). Typically, the complaint will be intermittent and usually occurs when driving over bumps or rough roads.
If DTC U0140 00 or U0073 71 is set only as a history code in any of the high speed modules, refer to “Testing for Electrical Intermittents” in the service manual to reset the DTC and diagnose the location of the fault.