Without Scan Tool

PROCEDURE
To display diagnostic trouble codes, use a Tech 1 scan tool. Grounding the Data Link Connector (DLC) will NOT flash Diagnostic Trouble Codes (DTCs), but will enable most outputs when the ignition is "ON" with engine "OFF". Grounding the DLC while the engine is running will cause the Malfunction Indicator Lamp (MIL) to flash to indicate "Open" or "Closed Loop". This is referred to as the "Field service Mode".