uh.........hmm. did you pull it from a fairly damaged foci? I could see it being broken, having its brains all shaken up in an accident..... I would say try one thing, and that's hook up the new IC, but disconnect the battery first (crap.....just a helpful hint from someone, if that's ok...negative first, then positive? dunno why I forgot

) anyway, do that, then press on your brake pedal till you lose any other power in the car...... or just leave it there for a couple hours or so. (probably not that long....) and hook up the IC, then reconnect the battery..... hopefully then it'll recognize the new tach when the car goes through its relearn process...... OH, and let it sit with the car on for a couple minutes......relearn process