Review the 'Possible Causes' mentioned above and visually examine the corresponding wiring harness and connectors. Ensure to check for any damaged components and inspect the connector pins for signs of being broken, bent, pushed out, or corroded.
B3891 02 Trailer Fog Lamps Circuit Short to Ground
B3891 04 Trailer Fog Lamps Circuit Open
To diagnose the B3891 code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour.
The Trailer Lighting Control Module receives a serial data message from the Body Control Module (BCM) indicating that the vehicle rear fog lamp have been activated. The Trailer Lighting Control Module responds by applying battery voltage to the trailer fog lamp control circuit illuminating the trailer fog lamps. The Diagnostic Trouble Code (DTC) sets when the Trailer Lighting Control Module detects a short to ground or an open/high resistance in the trailer fog lamps control circuit.
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