U029200 on Audi: Lost Communication With Drive Motor Control Module "B" (Unauthorized)
Diagnostic trouble code U029200 on Audi vehicles — what it means, the common
causes, and how to confirm the real fault before replacing parts.
What does U029200 mean?
U029200 indicates: Lost Communication With Drive Motor Control Module "B" (Unauthorized).
This relates to the Network / communication system.
Common causes of U029200
Control module disconnected from the CAN bus at least twice (bus OFF condition)
Fatal errors detected in the affected control module exceeding the internal error counter threshold
Message time-out due to at least 10 consecutive messages not received
Interruption of the fiber-optic cable (if on MOST bus)
Faulty voltage supply of the transmitter or receiver control module
Faulty transmitter or receiver control module
What to check (live data)
CAN bus message cycle time (delays indicate missing messages; threshold is 10 missed messages triggering time-out)
Internal error counter (threshold equivalent to max. 32 repeated messages)
Bus OFF event count (malfunction stored after at least 2 bus OFF events without intermediate communication)
Parts often involved in U029200
Drive Motor Control Module B
CAN bus wiring
Fiber-optic cable (if applicable)
Data Bus On Board Diagnostic Interface J533 (if applicable)
Don't replace parts until the root cause is confirmed — many of these codes are caused by wiring, a connector or an upstream fault, not the part itself.
Get the confirmed root cause for U029200 — on YOUR vehicle
A code is a symptom, not a diagnosis. AutoDX Pro cross-checks several
independent assessments, pinpoints the actual root cause, gives you the
exact tests to confirm it, and shows the parts — only after the cause is
confirmed. Reads your scan-tool photo and decodes your VIN with open
recalls.
U029200 is a diagnostic trouble code: Lost Communication With Drive Motor Control Module "B" (Unauthorized).
What are the common causes of U029200 on an Audi?
Common causes include: Control module disconnected from the CAN bus at least twice (bus OFF condition), Fatal errors detected in the affected control module exceeding the internal error counter threshold, Message time-out due to at least 10 consecutive messages not received, Interruption of the fiber-optic cable (if on MOST bus). The exact cause depends on the vehicle — confirm it before replacing parts.
Can I keep driving an Audi with U029200?
It depends on the fault and your symptoms. Some causes are minor, others can damage components or affect safety. Get the root cause confirmed before deciding.
How do I fix U029200 on an Audi?
Confirm the actual root cause with targeted tests first, then replace only the part that's at fault. AutoDX Pro gives you the root cause, the exact tests, and the parts for U029200 on your specific Audi.