[moltuae]

Originally Posted by MikkiJayne

The door switches are being bypassed by the interior light bulbs, so door open = 0Ω, door closed = 6Ω. As far as the cluster is concerned, 6Ω is the same as 0 so it thinks the other doors are open when they're not. The challenge is finding the stimulus that causes this to happen as it is not consistent.

There were wire taps all over the place under the dash. None near the central locking module, but there is one in the relay box which I'm going to investigate today.

There was some aftermarket footwell lighting which would come on and off seemingly at random which used a Raspberry Pi-grade latching circuit and a foglight switch The Pi-grade board is not automotive rated and so didn't cope well with fluctuating voltages etc and I found with the engine not running it would turn on and off if you moved the passenger seat backrest Not the driver's seat mind, or any of the other seat controls. Just the passenger seat backrest. No idea what weird effects that was having on the rest of the car's electronics, but it was also wired in with scotchlocks so its also gone.

Judging by that info and Vera's description of how the fault developed, it sounds to me like some after-market device has been tapped into the interior lighting circuit (to detect an open door) and that device has failed (or perhaps just lost power), causing the circuit to be pulled to earth at that junction.

My guess would be the 6Ω you are seeing is the combined resistance of the bulbs between the door switch and the unwanted path to earth. Are you getting 6Ω at every door switch? Any variation between them might give a clue as to where the fault lies.