GM Service Manual Online
For 1990-2009 cars only

Begin the system diagnosis with Diagnostic System Check - Vehicle. This procedure provides the following information:

    • The identification of the control modules which command the system
    • The ability of the control modules to communicate through the serial data circuit
    • The identification of any stored diagnostic trouble codes (DTCs) and the codes' statuses

The Diagnostic System Check identifies the correct procedure for diagnosing the system and indicates where that procedure is located.