Lost Communication With Trailer Brake Control Module
What does U0127 mean?
The U0127 code means the vehicle's onboard diagnostic system has detected: Lost Communication With Trailer Brake Control Module. This is a moderate severity code.
Common Symptoms
- Trailer brake warning light on
- Integrated trailer brake controller not functioning
- No trailer brake output detected
- Trailer sway control system disabled
- Check trailer wiring message on dash
Probable Causes (Ranked by Likelihood)
- Failed integrated trailer brake control module Very High
- Damaged wiring at trailer connector High
- Corroded trailer plug or vehicle receptacle Moderate
- Blown trailer brake controller fuse Moderate
- Aftermarket trailer brake controller interference Low
Step-by-Step Diagnostic Procedure
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Check the trailer brake controller fuse in the under-hood fuse box
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Scan for DTCs in the trailer module and body control module
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Inspect the trailer plug receptacle for corrosion or bent pins
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Verify power supply and ground at the trailer brake module
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Check for aftermarket trailer brake controllers that may conflict
Frequently Asked Questions
Can I drive with code U0127?
You can drive the vehicle itself, but do not tow a trailer without functioning trailer brakes. The integrated trailer brake controller will not apply the trailer brakes during stops.
What causes U0127?
The most common cause is a failed integrated trailer brake control module or corroded wiring at the trailer plug. A blown fuse is also a frequent and easy-to-fix cause.
Can I use an aftermarket brake controller instead?
If the integrated module has failed, an aftermarket trailer brake controller can be used as an alternative. However, it will not integrate with the vehicle stability and trailer sway control systems.