Since I reconnected my ECU after checking for oil, my speed-detected automatic door locking doesn't work, and also the rear parking sensors have now got a problem. When the car is put in to reverse, the warning alarm makes a constant tone for about 4 seconds, and then goes off, and the rear sensors themselves no longer work.

Any ideas?

No idea what caused these problems, but they have both started working again. All I did do was disconnect and reconnect the leads on the parking sensor unit behind the rear light cluster. Whether this had anything to do with them starting working again us anyone's guess.