A fault code doesn’t yet mean the unit or sensor itself is faulty: often it’s the plug and connector leading to it.
Possible causes
- Power or ground of this control unit (fuse)
- CAN bus connector or wire
- The control unit itself
- Low battery voltage
What you can do yourself
- Check the 12 V battery and terminals: at low voltage control units lose communication.
- Check this control unit’s fuse.
- Diagnosis with a scan tool that can access all control units is needed.
Stop and don’t drive on if:
- The instrument panel went dark or many warning lights came on at once
- Power steering is gone or the brakes don’t work as usual
OOleg’s tip: check the connector
Often the cause is simple — there is no contact in the connector (plug). Look at the connector from the back: remove the rubber seal and you will see whether a wire is corroded or has come off completely. Corrosion shows up as green deposits. Ideally, gently pull each wire towards you one at a time: a sound wire stays in place, while a corroded one simply comes off — it needs to be repaired.
Unplug and inspect connectors with the ignition off.
OA case from Oleg’s practice
- Range Rover 2015 Doesn’t detect the key and won’t start. We switched the ignition on by holding the key against the mark under the steering column. The fuses are intact, but the BCM doesn’t communicate (U0140) — next, check its power, ground and wiring. How it went ↗
On Oleg’s website:Car wiring repair ↗
The explanation comes from the error code reference in the AvtoElektrik PRO app.