B3891 Chevrolet Code - Trailer Fog Lamps Circuit
Quick Answer
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. Common causes include Faulty Trailer Fog Lamps, Trailer Fog Lamps harness is open or shorted, Trailer Fog Lamps circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- B3891 Chevrolet indicates Trailer Fog Lamps Circuit.
- Common causes
- Common causes include Faulty Trailer Fog Lamps, Trailer Fog Lamps harness is open or shorted, Trailer Fog Lamps circuit poor electrical connection.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code B3891 Chevrolet Description
What are the Possible Causes of the DTC B3891 Chevrolet?
- 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 to Fix the DTC B3891 Chevrolet?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
B3891 04 Trailer Fog Lamps Circuit Open
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the B3891 Chevrolet code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Frequently Asked Questions about B3891 Chevrolet Code
1. What does the OBDII code B3891 mean on a Chevrolet?
B3891 indicates an issue with the Trailer Fog Lamps Circuit, typically caused by a malfunction or open circuit in the trailer fog lamp wiring or related components.
2. What are the common symptoms of the B3891 code?
Symptoms include non-functioning trailer fog lamps, a warning light on the dashboard, or a stored fault code in the vehicle’s ECU.
3. What causes the B3891 code to appear?
Common causes include damaged or corroded wiring, a faulty trailer wiring harness, a defective fog lamp relay, or issues with the trailer control module.
4. Can a blown fuse cause the B3891 code?
Yes, a blown fuse in the trailer lamp circuit can trigger the B3891 code by disrupting the electrical connection.
5. How do you diagnose the B3891 code?
Start by inspecting the trailer wiring and connectors for damage or corrosion, check the fuse and relay for the fog lamp circuit, and test the continuity of the circuit using a multimeter.
6. Is it safe to drive with the B3891 code?
Yes, it is generally safe to drive, but the trailer fog lamps may not function, which could reduce visibility for other drivers in poor weather conditions.
7. How can you fix the B3891 code?
Repairs may include replacing damaged wiring, cleaning corroded connectors, replacing a blown fuse or faulty relay, or repairing the trailer control module if necessary.
8. Do you need to reprogram the ECU after fixing the B3891 code?
In most cases, reprogramming the ECU is not required. Clearing the code with an OBDII scanner after repairs is typically sufficient.
9. Can a faulty trailer cause the B3891 code?
Yes, if the trailer’s wiring or fog lamps are damaged or improperly connected, it can cause the B3891 code to appear.
10. How much does it cost to repair the B3891 code on a Chevrolet?
Repair costs vary but typically range from $50 to $200, depending on whether the issue involves simple wiring repairs or component replacements like a relay or module.
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