help needed clk320 cab.

[james69m@hotmail.com]

have a clk cab 320, as soon as i switch on the ignition it comes up lamp failure. the reversing lights do not operate and the wing mirrors will not tilt down. very occasionally when i start i don't get this message and every thing works fine. just had it in the dealer, and they cleared the fault codes and it worked fine for a day. then half way home it beeped again. needless to say it no longer works again. i'm a mechanic and have checked every connection i can find, and nothing makes a difference except clearing the fault codes. can anyone help? or has anyone heard of this fault before. james69m@hotmail.com
cheers :-(