What does code U0140 mean?
Symptoms seen in the workshop
- The engine does not start, or starts and stalls after a few seconds (immobilizer)
- Immobilizer warning light or MIL on
- BCM-dependent functions without signal (brake, clutch, cruise control)
- U0140 stored in other modules too
Common causes of code U0140
- Engine swap with its ECU into another chassis without the original BCM
- Engine outside the vehicle: boat, kit car, test bench
- Faulty BCM, no power supply or very low battery
- BCM replaced but not coded or paired with the ECU
- Damaged CAN wiring or faulty gateway
Fix by ECU remapping
ECU remapping solution for engines that will run without their BCM:
1. IMMO OFF (calibration): deactivation of the immobilizer in the engine ECU, so that it starts without the BCM permission.
2. DTC OFF: deactivation of U0140 and associated codes: U0422, U0155 and U0167, depending on the vehicle architecture.
If the vehicle keeps its BCM and it stops communicating, diagnose it instead (power supply, coding, CAN wiring). IMMO OFF should only be used where regulations allow it and on vehicles of verified origin.
⚠️ Important: Disabling the DTC without the correct calibration of the related system (IMMO OFF + DTC OFF) is not a valid fix. Both the calibration maps and the diagnostic mask have to be modified.
