The error code list is also in the user manual, but the error message you mention is not listed there.
I am only a hapless dilettante, but I do not think that "dusting" contacts is enough... There might be a strong oxidation on them. When I was rescuing my non-booting EIII, I used a cotton swab damped with a contact cleaner. It quickly became black with dirt!
Please, keep in mind, I cannot guarantee the procedure is technically correct, but it helped to me... At least I believe so...
Be extremely careful when manipulating with anything inside the unit! Above all, follow the "anti-static" rules, and MAKE SURE YOU DO NOT EXCHANGE POSITIONS OF THE RIBBON CABLES GOING TO OUTPUTS ! YOU WOULD BURN CIRCUITS !