GM Service Manual Online
For 1990-2009 cars only

Begin the system diagnosis with Powertrain On Board Diagnostic (OBD) System Check . The Powertrain On-Board Diagnostic (OBD) System Check will provide 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 their status.

The use of the Powertrain On-Board Diagnostic (OBD) System Check will identify the correct procedure for diagnosing the system and where the procedure is located.