Network, generic

U064D Lost Communication With Trailer Brake Control Switch

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Trucks with a factory trailer brake controller carry a dash switch with gain buttons and a manual slider that lets the driver apply only the trailer brakes. On current designs this switch is a small electronic unit that reports to the brake controller, which is why GM's 2024 campaign N242442100 for the 2022 Silverado and Sierra pairs a new switch with reprogramming of the cluster and the brake module. U064D marks a broken data link to that switch. No maker documents this code in public; GM logs switch faults as C159C, and in PIT5948B and campaign N222384930 a defective switch brought up the Service Trailer Brake warning and disabled trailer braking for that key cycle. The whole controller module silent is U0137, bad data from it U0438. Brake the trailer only with caution until fixed.

Likely causes

Trailer brake control switch electronics failed
Switch connector behind the dash trim loose or not seated
Damaged data or supply wire to the switch
Brake or cluster software not matched to a replaced switch

Symptoms

  • Service trailer brake message in the cluster
  • Gain buttons and manual slider have no effect
  • Electric trailer brakes not applied when braking

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–400
Time0.3–1.5 h

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

Parts involved

trailer brake control switchvehicle bus wiring

Related codes

U0137U0438

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, en.wikipedia.org.