What it means
The vehicle bus reports loss of communication with drive motor control module C. Torque commands for this EV/hybrid traction motor cannot be coordinated, forcing the powertrain into a degraded mode.
At a glance
- Usually lights the warning light of the system that lost communication
- The engine or gearbox may go into limp mode
How it works
Drive motor control module C coordinates torque commands for traction motor C in a hybrid or electric powertrain. U029B sets when the vehicle network no longer receives the module's messages, preventing normal coordination and potentially forcing the powertrain into a degraded mode.
Common causes
Most likely first.
- Bus wiring open or shorted
- Module without power or ground
- Module failed
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Scan all modules and save freeze-frame and related drive-motor or network codes to determine whether module C alone has stopped communicating.
- Check the 12-V battery and scan-tool module status, since weak low-voltage supply can keep the motor controller offline.
- Inspect accessible connectors and low-voltage bus wiring at drive motor control module C for damage, corrosion, looseness, or heat marks.
- Check module C's power and ground circuits under load using vehicle wiring information and the manufacturer's specification.
- Test the communication wiring for opens, shorts, or poor connections; consider the module only after its power, ground, and bus circuits pass.
Common fixes
- Repair a loose or damaged connector at drive motor control module C.
- Repair an open, short, or poor connection in module C's bus wiring.
- Restore a faulty power or ground supply to module C.
- Replace drive motor control module C if its supplies and communication circuit are sound but it remains offline.
Can I keep driving?
Avoid driving if propulsion is reduced, unpredictable, or interrupted; loss of motor C coordination can leave the vehicle with limited power or cause it to stop. Arrange prompt diagnosis and do not work on high-voltage parts.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.