Had my front pads replaced by an audi dealer last week (they were about 90% worn, but no warning light was on) and now a week later my brake warning light has come on! Rang the dealer and they can't fit me in for a fortnight! Am I right in thinking only the front brakes have a sensor (i.e. its not the car telling me the back ones need doing?) Would worn discs cause this iight to come on? finally, is it safe to drive around for a couple of weeks with the warning light on? (There's no noise when braking, although there was a slight crunch when reversing slowly yesterday).