U029BLost Communication With Drive Motor Control Module C
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- Drive motor control module C is the inverter and controller of a third traction motor, so it only occurs on vehicles with three or four drive motors. Production examples are the tri-motor version of the GMC Hummer EV, which drives its rear axle with two motors, and Rivian's quad-motor R1T and R1S with one motor per wheel. U029B is stored when the propulsion or vehicle controller stops receiving any periodic messages from module C. Frames that still come but carry unusable values are U059C; U0292 and U029C cover the second and fourth motor controllers. Which motor gets letter C is the maker's decision, and no manufacturer documents U029B publicly. For hybrids, CARB 1968.2 demands that missing communication from digital inputs be detected. Expect that motor to be shut off and reduced power and traction.
- What you may notice
- Reduced power warning, one motor disabled
- Torque vectoring or all-wheel-drive functions unavailable
- Drive system warning in the cluster
- Likely causes
- PossibleFuse, low-voltage supply or ground of module C faulty
- PossibleDamaged or corroded bus wiring or connector at the drive unit
- PossibleSoftware fault or interrupted programming of module C
- RareDrive motor control module C internally failed
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €6,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.