ERR3 AFAIK is a failure of the load mechanism.
I have found what MAY be the problem...
Removed the radio, the Front face is held in place with a small screw on the underside and a series of plastic clips.
Undo the screw, prise the clips and remove the face.
There is an switch behind the face directly behind the 'LOAD' button.
On the unit I found with this fault, the switch was broken, presumably from heavy-handed disc insertion.
soldering together the switch contacts or adding some sort of switch MAY get the unit working again.
kukimonster, January 2009