GM Service Manual Online
For 1990-2009 cars only

A Diagnostic Starting Point

Begin the system diagnosis with the A Powertrain On-Board Diagnostic (OBD) System Check. The Powertrain OBD System Check will provide the following information:

    • The identification of the control module(s) that command the system.
    • The ability of the control module(s) to communicate through the serial data circuit.
    • The identification of any stored diagnostic trouble codes (DTCs), and DTC statuses.

The use of the Powertrain OBD System Check will identify the correct procedure, and the location of the procedure to properly diagnose the system.