U1400 — Powertrain data bus / communication fault (VAG-specific variant)
Reference detail for fault code U1400 on the DQ200 DSG transmission family.
What U1400 indicates
The DQ200 transmission control unit stores U1400 when it detects the following condition: Powertrain data bus / communication fault (VAG-specific variant). 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 | U1400 |
|---|---|
| Transmission | DQ200 (7-speed dry DSG) |
| Factory code | 0AM/0CW |
| Category | Communication |
| Status | Documented — review advised |
This code is documented but not independently confirmed. Confirm it against the specific vehicle before ordering any part.
Have this code on your vehicle?
Send us the code and the vehicle details and we will confirm the correct unit or part by email.
Related pages for the DQ200
DQ200 repair
Symptoms, mechatronic issues and what repair involves for this family.
DQ200 mechatronics
Replacement mechatronic unit and exchange options for this family.
DQ200 parts
Selected parts most often involved in repair for this family.
DQ200 fault codes
Every documented code for this family in one table.
Have a fault code to check?
Send us the code and the vehicle details and we will confirm the correct unit or part by email.