I have a 97, after I got a buddy to install a stereo I started having electrical problems and this same thing happened to my dic. I eventually pulled the deck out to find he had connected the wires with electrical tape and some had came off and all the bare wires were touching so I got that fixed and everything started to work right again I had to unhook the battery after that to the dic to work so I'm guessing it got short circuited. So I suggest you look for a any similar electrical gremlins fix them and reset the computer. Hopefully this helps.
