U0137 Code – Lost Communication With Trailer Brake Control Module

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Fault Code Description

The U0137 Diagnostic Trouble Code (DTC) indicates that one or more control modules have lost communication with the Trailer Brake Control Module (TBCM) over the Controller Area Network (CAN) bus. The Trailer Brake Control Module manages the operation of the electronic trailer braking system, ensuring proper brake force is applied to the trailer during towing. When communication is interrupted, the towing system may be disabled and the U0137 code will be stored.

Symptoms

  • Check Engine Light or trailer brake warning light illuminated.
  • "Service Trailer Brake System" message displayed.
  • Trailer brakes fail to operate correctly.
  • Reduced towing stability and braking performance.
  • Additional CAN communication DTCs may be stored.

Common Causes

  • Open or short circuit in CAN High or CAN Low wiring.
  • Blown fuse supplying the Trailer Brake Control Module.
  • Poor battery voltage, power supply, or ground connection.
  • Loose, damaged, or corroded electrical connectors.
  • Faulty Trailer Brake Control Module.
  • Incorrect module programming after replacement.

Severity

Severity: Moderate to High. Normal vehicle driving may not be affected, but trailer braking performance can be reduced or completely disabled. If towing a trailer, the issue should be repaired immediately to maintain safe braking.

Average Repair Cost

  • CAN bus wiring repair: $100–$350
  • Power or ground circuit repair: $80–$250
  • Connector cleaning or replacement: $50–$200
  • Fuse replacement: $10–$50
  • Trailer Brake Control Module programming: $100–$300
  • Trailer Brake Control Module replacement: $300–$900+

Diagnosis

  1. Scan all vehicle modules for stored DTCs.
  2. Inspect the Trailer Brake Control Module fuse.
  3. Verify battery voltage, power, and ground circuits.
  4. Inspect CAN High and CAN Low wiring.
  5. Check connectors for corrosion or loose terminals.
  6. Verify communication using a professional scan tool.
  7. Reprogram or replace the Trailer Brake Control Module if necessary.

Common Repairs

  • Repair damaged CAN bus wiring.
  • Replace blown fuses.
  • Repair power or ground circuits.
  • Clean or replace damaged electrical connectors.
  • Reprogram the Trailer Brake Control Module.
  • Replace the Trailer Brake Control Module if confirmed faulty.

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