U0101 — Lost communication with transmission control module (TCM)
Reference detail for fault code U0101 on the 0DR transmission.
What U0101 indicates
The 0DR transmission control unit stores U0101 when it detects the following condition: Lost communication with transmission control module (TCM). The fault concerns data communication between the transmission control unit and other control units on the powertrain CAN bus. The code is stored when messages are missing or corrupted, or the bus hardware reports an error. A stored code does not by itself prove that a part has failed. Before replacing anything, check the live data, wiring, connectors, power supply and fluid condition, and confirm the fault on the vehicle.
Symptoms
- Gear display missing or flashing
- Emergency mode
- Several control units reporting communication faults
- Transmission not reachable with the diagnostic tester
Possible causes
- Wiring or connector fault on the CAN bus
- Power supply or ground fault at the control unit
- Faulty transmission control unit
- Fault in another control unit on the same bus
Related components
Powertrain CAN bus · Transmission control unit (TCU) · Connectors and wiring
| Fault code | U0101 |
|---|---|
| Transmission | 0DR (Automatic transmission (Tiptronic)) |
| Factory code | 0DR (AL550) |
| Category | Communication |
| Status | Documented — review advised |
This code is documented but not independently confirmed. Confirm it against the specific vehicle before ordering any part.
Generic OBD-II transmission code (SAE J2012). The meaning is standard; the cause on this transmission should be confirmed by diagnosis.
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