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Entering Self-Diagnostics

The vehicle is equipped with an Assembly Line Data Link (ALDL) diagnostic connector. This connector is located in the passenger compartment. If the diagnostic terminal is grounded with the Key On and Engine Off (KOEO) the system will enter the Diagnostic Mode. If the diagnostic terminal is grounded when the engine is running, Key On Engine Running (KOER), the system will enter Field Service Mode.

Fig 1: Assembly Line Data Link (ALDL) Diagnostic Connector
G94607Courtesy of GENERAL MOTORS CORP.