U0438 code meaning
Invalid Data Received From Trailer Brake Control Module
What U0438 means
U0438 names the trailer brake control module, which applies the electric brakes of a towed trailer in step with the vehicle's braking; park brake data has a code of its own, U0417. Ford uses U0438 explicitly: SSM 52184 connects U0438:82 stored by the cluster of some 2023 F-150 PowerBoost hybrids, built from 24 to 26 October 2022, with a Trailer Brake System Fault message caused by the cluster configuration, which is re-run with the dealer tool. SSM 53980 for 2023-25 Super Duty blames U0438 together with other network codes on an incorrectly tightened ground G201 (8 ± 1.2 Nm). Saab's 2011 9-5 list knows subtype 71. The driver sees a trailer brake warning and gain control may not work. U0137 is lost contact.
U0438 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0438
- Trailer brake system fault message
- Trailer brake gain cannot be set or trailer brakes inactive
- Further network warnings in the cluster
Common causes of U0438
- Most likelyReceiving module (instrument cluster) wrongly configured
- PossibleLoose or wrongly tightened body ground
- Less likelyInternal fault of the trailer brake control module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Trailer brake moduleCAN bus wiring
What each part of U0438 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 38 | The exact fault in that area. |
What to do next
- Note U0438 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0438
What does U0438 mean?
U0438 means "Invalid Data Received From Trailer Brake Control Module". U0438 names the trailer brake control module, which applies the electric brakes of a towed trailer in step with the vehicle's braking; park brake data has a code of its own, U0417. It is a generic code, so it means the same on every make.
Is it safe to drive with U0438?
U0438 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U0438 fail an emissions test?
U0438 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0438 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2 hours of work. This is a job for a workshop.
Will U0438 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.