GM Service Manual Online
For 1990-2009 cars only

Begin the system diagnosis with Diagnostic System Check - Alternative Fuels (Engine Controls) . The Diagnostic System Check-Engine Controls 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 the codes' statuses

The use of the Diagnostic System Check-Engine Controls will identify the correct procedure for diagnosing the system and where the procedure is located.