Network, generic

U029B Lost Communication With Drive Motor Control Module C

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Fuse, low-voltage supply or ground of module C faulty
Damaged or corroded bus wiring or connector at the drive unit
Software fault or interrupted programming of module C
Drive motor control module C internally failed

Symptoms

  • Reduced power warning, one motor disabled
  • Torque vectoring or all-wheel-drive functions unavailable
  • Drive system warning in the cluster

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–6,000
Time1–6 h

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

Parts involved

drive motor control module cvehicle bus wiring

Related codes

U029CU0292U059C

References: law.cornell.edu, en.wikipedia.org, en.wikipedia.org.