B166C
Left Trailer Tow Lamp Control Circuit High
B166C is an OBD-II diagnostic trouble code meaning: Left Trailer Tow Lamp Control Circuit High. Common causes: short circuit to positive in the control circuit, trailer lamp relay malfunction. Estimated repair cost: $22–111.
Symptoms
- Left trailer light flashing or not working
- Check Engine Light Is On
- Inability to activate trailer function
Causes
- Short circuit to positive in the control circuit
- Trailer lamp relay malfunction
- Wiring harness damage
- Problems with the trailer control unit
How to Fix
- Check the integrity of the wiring harness to the left trailer lamp
- Check control circuit relays and fuses
- Diagnose the trailer control unit for errors
- Replace damaged components
Related codes
FAQ
What does the B166C code mean?
B166C is an OBD-II diagnostic trouble code that indicates: Left Trailer Tow Lamp Control Circuit High
What causes a B166C error code?
The most common causes of B166C include: Short circuit to positive in the control circuit; Trailer lamp relay malfunction; Wiring harness damage; Problems with the trailer control unit.
How do I fix a B166C diagnostic trouble code?
To fix B166C: Check the integrity of the wiring harness to the left trailer lamp. Check control circuit relays and fuses. Diagnose the trailer control unit for errors. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with B166C?
Limited driving only, diagnose soon
How much does it cost to fix B166C?
The estimated repair cost for B166C is $22–111. Actual cost depends on your vehicle, location, and labor rates.
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