Thank for the quick responses. Yes, the door panels have been off but they have both been refitted by me and I am sure that the speaker cables are connected. The speakers are sceured in the doors and only one has ever been removed to test it when the problem first arose, the speaker works fine so on to the BM54.

Thank you for the pointer BB, any chance that anyone could describe what the part looks like so that I can locate it and secondly, is it simply a case of swapping it for a new one or can it be either bypassed or repaired?