U064D code meaning
Lost Communication With Trailer Brake Control Switch
What U064D means
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.
U064D at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U064D
- Service trailer brake message in the cluster
- Gain buttons and manual slider have no effect
- Electric trailer brakes not applied when braking
Common causes of U064D
- Most likelyTrailer brake control switch electronics failed
- PossibleSwitch connector behind the dash trim loose or not seated
- Less likelyDamaged data or supply wire to the switch
- Less likelyBrake or cluster software not matched to a replaced switch
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Trailer brake control switchVehicle bus wiring
What each part of U064D means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4D | The exact fault in that area. |
What to do next
- Note U064D 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 U064D
What does U064D mean?
U064D means "Lost Communication With Trailer Brake Control Switch". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U064D?
U064D does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U064D fail an emissions test?
U064D 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 U064D to fix?
Difficulty: medium. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U064D clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.