Right my family car is an e39 2003 530d sport, at the mot it failed on a rear number plate light out. Now after checking the bulb and finding 0volts at the bulb holder. Quick google revealed common problems with the tailgate wiring. Right so I peeled back the wiring grommet to find broken wires, did I quick repair and the light works.

At the same time I found problems with the central locking not working intermittently, so I removed the tailgate wiring completely and rewired it longer with neat solder joints, everything was working fine, but the central locking glitched once today, which is infuriating! Now where else could this problem be coming from, googling takes me down a million possible faults! Is there a way of diagnosing central locking faults with a pc? Obd covers power train only I think??

Cheers