Lost Communication With All-Terrain Control Module
What does U0138 mean?
The U0138 code means the vehicle's onboard diagnostic system has detected: Lost Communication With All-Terrain Control Module. This is a moderate severity code.
Common Symptoms
- Terrain management system warning light on
- Terrain mode selection not working
- Vehicle stuck in one drive mode
- Hill descent control not available
- Crawl control or off-road systems disabled
Probable Causes (Ranked by Likelihood)
- Failed all-terrain control module Very High
- Damaged CAN bus wiring to terrain module High
- Terrain mode selector switch failure Moderate
- Corroded connector at terrain control module Moderate
- Module software issue requiring update Low
Step-by-Step Diagnostic Procedure
-
Scan for DTCs in all drivetrain and chassis modules
-
Check CAN bus wiring and connector at the terrain control module
-
Verify power supply and ground at the module
-
Test the terrain mode selector switch for proper operation
-
Check for available software updates for the terrain module
Frequently Asked Questions
Can I drive with code U0138?
You can drive short distances on paved roads. The all-terrain control features including terrain modes and hill descent control will not be available. Avoid off-road driving.
What causes U0138?
A failed all-terrain control module is the most common cause. These modules manage the terrain response system, hill descent, and crawl control features.
Will the vehicle still work in 4WD?
Basic 4WD functionality may still work through the transfer case, but the advanced terrain management features will be disabled. The vehicle may default to a standard drive mode.