I feel your pain. Mine ('89 idi) had/has the same issue with the tach. Tach reading 0, tranny won't work. Tach reading, tranny shifts great. I replaced the ECM with a rebuilt one. Not much better until one day the wife hit the dash console hard ( on purpose while she was cleaning ) and the tach started to work. It's got to be a bad connection or ground wire in there. Somewhere. I haven't had time to pull it all apart and if it quits ( rarely anymore) it will start working again pretty quick.
Thanks, GNATHV, for the diagram!
P.S. I really hate wiring issues...
Thanks, GNATHV, for the diagram!
P.S. I really hate wiring issues...