For what it's worth, I needed the code reset on my 87 Grand Prix. Took in into the dealer who hooked up a machine to the unit and it took all of ten seconds and no charge...

You might also want to see if the unit has a fuse on the back. I've heard when they start to go (my fuse didn't like having the power cut and then reconnected) you can have random problems (ala the 7 not working?)

John

87 420SEL
00 C230K
00 A4 2.8Q