GM Service Manual Online
For 1990-2009 cars only

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

    • The identification of the control module which commands the system
    • The ability of the control module or modules to communicate through the serial data circuit
    • The identification and status of stored diagnostic trouble codes  (DTCs)

The use of Diagnostic System Check - Vehicle identifies the correct procedure for diagnosing the system and where the procedure is located.

Symptoms

When it has been determined through Diagnostic System Check - Vehicle that no DTCs are present, begin symptom diagnosis by reviewing Functional Test . This helps you determine if the condition described by the customer is normal or if a condition exists. If it is determined that a condition exists, identify the condition by referring to Symptoms - Automatic Transmission . Symptoms - Automatic Transmission provides common diagnostic categories which relate directly to diagnostic information and procedures.