Hi, after more than 20 years of Audi's our latest is a 2009 A3 quattro. I know the 4x4 transfer box quattro system needs periodic servicing, can anybody tell me what needs doing. I do not have a manual for this car.

Also, the central lock on drivers door more often than not does not unlock on remote and needs the key to open it. If listen to the door closely the solenoid can be heard operating though, so I do not think it is electrical. Is there a common issue to find causes this symptom?