I have a 1990 Beretta GTZ. 2.3l quad 4 engine. The "service engine soon" light comes on and stays on. Car does start. Hooked a jumper wire to the A and B terminals to pull the codes and I get nothing. The light just stay on. I checked the ground on the A terminal and it is good. Don't know if this makes any difference but the cooling fan alway comes on, even even with AC turned off, defroster turned off, etc. Is the ECM/PCM toast? It idles pretty high. Disconnecting the battery does not turn off the light. Help!