B3891 - Trailer Fog Lamps Circuit

Repair Importance Level: 3/3
Repair Difficulty Level: 3/3    What is this?
Table of contents

B3891 Possible Causes

  • Faulty Trailer Fog Lamps
  • Trailer Fog Lamps harness is open or shorted
  • Trailer Fog Lamps circuit poor electrical connection
  • Faulty Trailer Lighting Control Module

How do I fix code B3891?

Check the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
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Tech Notes

B3891 02 Trailer Fog Lamps Circuit Short to Ground
B3891 04 Trailer Fog Lamps Circuit Open

Cost of diagnosing the B3891 code

Labor: 1.0

The cost of diagnosing the B3891 code is 1.0 hour of labor. The auto repair labor rates vary by location, your vehicle's make and model, and even your engine type. Most auto repairs shops charge between $75 and $150 per hour.

Possible Symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)

B3891 Description

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.
OBDII Code B3891 - Trailer Fog Lamps Circuit - AutoCodes.com

More Information

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