GM Service Manual Online
For 1990-2009 cars only

All DTCs can be displayed by using one of the following methods:

    â€¢ A scan tool
    â€¢ The On-Board Service Diagnostic (OBSD)

Most of the diagnostic tables will refer to the scan tool for diagnostic support. For details on using the OBSD to display and/or clear DTCs, refer to OBSD Procedure.