Network, generic

U0438 Invalid Data Received From Trailer Brake Control Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Receiving module (instrument cluster) wrongly configured
Loose or wrongly tightened body ground
Internal fault of the trailer brake control module

Symptoms

  • Trailer brake system fault message
  • Trailer brake gain cannot be set or trailer brakes inactive
  • Further network warnings in the cluster

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€40–600
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

trailer brake modulecan bus wiring

Related codes

U0137U0417U064D

References: static.nhtsa.gov, static.nhtsa.gov, saabwisonline.com.