U0138 Code – Lost Communication With All Terrain Control Module

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Fault Code Description

The U0138 Diagnostic Trouble Code (DTC) indicates that one or more control modules have lost communication with the All Terrain Control Module (ATCM) over the Controller Area Network (CAN) bus. The All Terrain Control Module manages selectable terrain modes such as Snow, Mud, Sand, Rock, and other off-road driving settings by coordinating multiple vehicle systems. When communication is interrupted, the terrain management system may be disabled and the U0138 code will be stored.

Symptoms

  • Check Engine Light or terrain system warning light illuminated.
  • Terrain Management System unavailable message.
  • Selected drive modes cannot be changed.
  • Reduced off-road 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 All Terrain Control Module.
  • Poor battery voltage, power supply, or ground connection.
  • Loose, damaged, or corroded electrical connectors.
  • Faulty All Terrain Control Module.
  • Incorrect module programming after replacement.

Severity

Severity: Moderate. The vehicle is usually safe to drive on normal roads, but terrain management functions and off-road driving modes may be unavailable, reducing traction and vehicle capability in challenging conditions.

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
  • All Terrain Control Module programming: $100–$300
  • All Terrain Control Module replacement: $400–$1,200+

Diagnosis

  1. Scan all vehicle modules for stored DTCs.
  2. Inspect the All Terrain 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 All Terrain 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 All Terrain Control Module.
  • Replace the All Terrain Control Module if confirmed faulty.

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