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Entering Self-Diagnostics

Vehicle is equipped with an Assembly Line Data Link (ALDL) diagnostic connector, located in passenger compartment.

The ALDL connector is grounded by connecting a jumper wire between terminals "A" (ground) and "B" (diagnostic terminal). See Fig 1 . If the diagnostic terminal is grounded with the ignition switch on and engine off, system will enter diagnostic mode. If the diagnostic terminal is grounded when the engine is running, Key On Engine Running (KOER), system will enter field service mode.

Fig 1: Identifying ALDL Diagnostic Connector Terminals
G94607Courtesy of GENERAL MOTORS CORP.