Folks, I have a 1980 car with a GM Iron Duke 2.5 L and the C4 emission control system. I have a technical manual and have done some diagnostics. I need to get it to pass CA smog.
I have replaced the ECM with a rebuilt one from NAPA. I have also replaced the tachometer filter which had an intermittent problem. The problem now is that the car will not go into closed loop mode (engine warmed up, etc.) unless the test lead from the ECM is grounded. It reads a code 12 when that happens. The other symptom is that when I hook a dwell tach to the tachometer test lead in the wiring harness, the engine dies (ignition is grounded out). I think there is a ground wire missing somewhere, but I need help.
Reply to piper snipped-for-privacy@prodigy.net Skip the x.
Thanks