I am driving Audi A6, C5 2001, VIN:WAUZZZ4BZ1N126373, installed factory fitted Concert Plus (Radio, Cassette, CD Changer), Nokia Handset, Navigation. Under normal operation music is paused upon incoming call and answered hands free which means its routed through cars music system. Since last week "Telephone" is displayed continuosly on Head Unit, unable to switch between any other functions i.e Radio, CD or cassette. The head unit is taken out and checked by technician, no faults found but as soon as its connected back in car "Telephone" appears again. Its noticed that removing one of the jacks, the head unit works normally but I cant receive/answer incoming telefone calls hands free, instead telephone is working through handset. The electrician has checked all wirrings and didnt find any problems with it. Please advise how the factory fitted equipment is installed! i.e Concert Plus, Telephone & Navigation. Where can I find wirring layout for Music, Telefone & Navigation unit? Any suggestions will be much appreciated. Thanks