OBD Guide

C111B

Trailer Brake Power Control Module System Voltage Voltage Below Threshold

C111B is an OBD-II diagnostic trouble code meaning: Trailer Brake Power Control Module System Voltage Voltage Below Threshold. Common causes: battery or alternator problems, damaged wiring harness. Estimated repair cost: $56–167.

Severity
⚠️ Medium
Can you drive?
Limited driving only, diagnose soon
Approx. repair cost
$56–167 (est.)

Symptoms

  • Trailer brakes do not work
  • The brake system fault indicator lights up
  • Reduced trailer braking performance

Causes

  • Battery or alternator problems
  • Damaged wiring harness
  • Trailer brake control module malfunction
  • Short circuit in the circuit
  • Poor contact in connectors

How to Fix

  1. Check the voltage on the battery and generator
  2. Inspect the wiring harness for damage
  3. Check the control module connectors for oxidation or poor contact.
  4. Test the trailer brake control module
  5. Replace faulty components

Related codes

FAQ

What does the C111B code mean?

C111B is an OBD-II diagnostic trouble code that indicates: Trailer Brake Power Control Module System Voltage Voltage Below Threshold

What causes a C111B error code?

The most common causes of C111B include: Battery or alternator problems; Damaged wiring harness; Trailer brake control module malfunction; Short circuit in the circuit.

How do I fix a C111B diagnostic trouble code?

To fix C111B: Check the voltage on the battery and generator. Inspect the wiring harness for damage. Check the control module connectors for oxidation or poor contact.. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with C111B?

Limited driving only, diagnose soon

How much does it cost to fix C111B?

The estimated repair cost for C111B is $56–167. Actual cost depends on your vehicle, location, and labor rates.

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