U029C code meaning
Lost Communication With Drive Motor Control Module D
What U029C means
Letter D refers to the controller of a fourth drive motor, which presupposes individual-wheel drive. Rivian's quad-motor R1S is the familiar production case: each wheel gets its own frame-mounted Bosch motor, so torque can be split freely between all four corners at any time. U029C says module D has gone silent on the network. If it still sent frames with bad content, U059D would be stored instead; a silent third motor is U029B. No manufacturer documents U029C publicly, so which wheel letter D belongs to and how the car reacts are vehicle-specific. CARB 1968.2 obliges hybrid OBD systems to notice when a digital input stops communicating. A plausible response is to drop the silent motor, cap the torque on the other side so the car still runs straight, and warn of reduced power.
U029C at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U029C
- Reduced power and loss of torque vectoring
- Drive system warning in the cluster
- Uneven traction when accelerating
Common causes of U029C
- PossibleFuse, low-voltage supply or ground of module D faulty
- PossibleBus wiring near the wheel drive unit chafed or wet
- Less likelySoftware fault or failed update of module D
- Less likelyDrive motor control module D internally failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Drive motor control module dVehicle bus wiring
What each part of U029C means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 9C | The exact fault in that area. |
What to do next
- Note U029C 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 U029C
What does U029C mean?
U029C means "Lost Communication With Drive Motor Control Module D". Letter D refers to the controller of a fourth drive motor, which presupposes individual-wheel drive. It is a generic code, so it means the same on every make.
Is it safe to drive with U029C?
Drive gently and only to a workshop. With U029C the car can go into limp mode (reduced power) to protect itself.
Will U029C fail an emissions test?
U029C 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 U029C to fix?
Difficulty: workshop only. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will U029C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.