HT4100 4.1, 4.5, 4.9 Discussion, Non GM parts=sick Cadillac?? in Cadillac Engine Technical Discussion; My 1992 Deville 4.9 most certainly suffers from electrical problems. The engine can, and has, run perfectly. Just not always. ...
My 1992 Deville 4.9 most certainly suffers from electrical problems. The engine can, and has, run perfectly. Just not always. We replaced many things, distributer, MAP sensor, ECM, etc etc.
The ECM came from our local parts place,not GM. We have since had cause to doubt the parts from this place. Is it possible for an ECM to be bad? Should we consider getting the ECM from the dealer? Will the ECM from the dealer be better? The price difference itself is questionable. I have a feeling my parts dealer was selling "If if sounds to be good to be true, it probably is" merchandise, as the prices were substanially lower.
I don't have my FSM handy but IIRC code 30 means that the ECM tries to bring the idle to the optimal range and yet it is unable to do so within a specified time limit. IIRC, the idle can either be too high or too low to trigger that code.
Basically it says that the ECM tried to adjust the ISC up or down to bring the rpms to the requested range but it was unable to do so.