GM Service Manual Online
For 1990-2009 cars only

Begin the system diagnosis with Diagnostic System Check - Vehicle in Vehicle DTC Information. The system check will provide the following information:

    â€¢ The identification of the control modules which command the system
    â€¢ The ability of the control modules to communicate through the serial data circuit
    â€¢ The identification of any stored DTCs and their status

The use of the system check will identify the correct procedure for diagnosing the system and where the procedure is located.