I had this error when I put the CD's in upside-down. Also it should give you the message if the CD cartridge doesn't engage fully. I do know this from a recent modification: un-plug the harness (on the front side of the changer) then re-insert it...this will basically reset the unit. It has power at all times, so unless the harness is disconnected, or the battery is disconnected it won't re-calibrate. Try this if you don't find anything else obvious...it just may work!