Hoping for some input before I throw money at this.
Background: I've had a cluster of intermittent electrical faults. They don't all fire at once — it's almost like the BCM is cycling through them. Removing fuses doesn't stop it, and I can't find any shorts. The symptoms so far:
- Van unlocking itself and setting the alarm off (most persistent and annoying)
- Parking assist unavailable
- Hill assist unavailable
- Fuel gauge not stable
- Central locking constantly locking/unlocking while driving
- Battery draining from the van constantly unlocking and trying to arm the alarm
UPDATE – latest and where I'm stuck:
An auto electrician has been through it. He found some wires near the fuel filter rubbing on the chassis and repaired those, but the issues are still happening. Also added a new earth at top of engine.
It's now getting worse and the van is becoming unresponsive. It'll start and do its usual weirdness, but when you stop the engine and lock the doors, the alarm goes off, then the key goes completely dead — you can't start it. The only fix is to disconnect the battery and leave it a good hour before it'll start again. The auto electrician reckons this is the BCM dropping into a failsafe/lockdown mode.
To rule things out, I've now got it stripped right back:
- Both driver and passenger doors completely unplugged
- Wiring harness to the rear of the van disconnected
- A lead by the AdBlue tank that had corrosion — disconnected
- Wiring to the exhaust/cat — disconnected
- Tried starting with no fuses in the BCM at all (starts, no dash obviously, but the same fault still occurs)
I'm reluctant to just fit a new BCM: if there's an underlying short or supply/earth fault, I'll have wasted the money and it'll do the same thing again. At this point I don't feel safe driving it.
Has anyone seen this failsafe/lockdown behaviour on a Relay/Boxer/Ducato, and what was the root cause? Any pointers on confirming a BCM-to-ECU comms loss without full dealer kit would be much appreciated.
