Hi all when I bought my 523 the air bag light was on and other things was not working so i went through loads of different things and narrowed it down to the little black box on thee back of the ignition switch and now I bought one it all works. If anyone who has an air bag light on and when you press the horn this is the fault or if your key just spins round hope this will help others and save you them huge bmw bills just to tell you they can not find a fault