My wife had a blazer that would do that crap....the passlock system is a piece of crap....what you can do is a search on bypassing the system. There is some great info about finding the right resistance and just soldering in a resister....I didn't get to that point with her blazer cause I sold it....btw the dealer wanted $400 to replace the ignition switch (passlock module).

Also, try undoing the battery cable ALL night on a weekend when you have time to really let that computer reset. Especially if you said the speedo was pegged out.

 

yeah, im leaving it disconnected all night, we`ll see what that does. i appreciate the info, ill look into it. thanks for the reply.

 

Had the bad running crazy gauges stuff with a blown alternator voltage regulator and blown MSD 6A. Do you get 13.6 volts accross the alt at fast idle?