Could be a few things, reset it and leave it a few days then see if the code comes back.
If it does come back it could be a camshaft angle sensor issue but it could also be a stretched timing chain causing the camshafts to be slightly out of alignment with each other, that results in one being more retarded than it should be which is then picked up by the sensors and logged in the ECU as a retarded code.
The reason I say try clearing it is that sometimes you can get a code thrown up randomly when starting the engine.
Has your engine management light come on at all ? when the car is cold and you first start it can you hear any ticking/tapping coming from one side of the engine when your standing outside the car ?
there is a service light on and it is saying the rear pads but I have just replaced the rear discs and pads do I have to take it to BMW to get rid of the light