XC40 Door Lock Failure

Sounds familiar! I had a similar issue with my old Peugeot 308. The symptoms were almost identical – central locking went haywire on one door. In my case, it turned out to be a corroded connector in the wiring harness that feeds the door sensor. It's like a kink in the garden hose, stopping the signal from getting through.

Interesting. Where exactly was the corroded connector located on your Peugeot? Was it difficult to access and diagnose?

On the Peugeot, it was inside the rubber boot where the wiring harness passes from the body into the door. A real pain to get to! I spent ages fiddling with it. Given the symptoms and the probable cause, I think you should consider visiting a trusted workshop. My repair bill was very similar to your probable repair costs.

Thanks for the helpful information! I took it to my local mechanic, and it turned out to be a defective plug connection, just as suspected. 95€ later, and the door locks are working perfectly again.