Test Description

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

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. Checks for DTCs for each module of the system.
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.

Fig 1: Diagnostic System Check - Navigation System

Courtesy of GENERAL MOTORS CORP.