GM/Detroit 6.5L ENGINE CONTROLS – Data Link Connector Diagnosis

Refer to Power, Ground, MIL and DLC.
Circuit Description
There should always be a malfunction indicator lamp (MIL) when the ignition is ON and the engine is OFF. Battery ignition voltage is supplied to the lamp.
The PCM will ti ‘rn the lamp ON by grounding the ignition feed circuit.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. This step verifies if the problem is in the scan tooor the vehicle.
6. This step will check the ground circuits at the DLC connector.
9. The step will check for the battery and ignition feeds to the PCM.


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