Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. 4. 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. 5. The symptom list in Symptom will determine the correct diagnostic procedure to use.
3. 6. The presence of DTCs which begin with "U" indicate some other module is not communication. The specified procedure will complied all the available information before tests are performed.
   Fig 1: Diagnostic System Check - Engine Electrical (1 Of 2)

   Courtesy of GENERAL MOTORS CORP.

Fig 2: Diagnostic System Check - Engine Electrical (2 Of 2)

Courtesy of GENERAL MOTORS CORP.