Test Description

The numbers below refer to the step numbers on the diagnostic table. See Fig 1.

1. 2
   
   Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 3
   
   The symptom list in Symptoms will determine the correct diagnostic procedure to use.
3. 4
   
   The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.
4. 6
   
   At this point you have determined all DTCs applicable to the Body Rear End system. Refer to SYMPTOMS - BODY REAR END  for further Body Rear End diagnosis. Any other codes displayed from the listed modules do not apply to Body Rear End and should be diagnosed in their applicable section.
Fig 1: Diagnostic System Check - Body Rear End Table
Courtesy of GENERAL MOTORS CORP.