Hi hammerpete here . I'm working on a 1990 buick reatta 3.8l auto with a check engine lite on for a code 56 quad driver b . I can not find any info on this , some say a bad ecm , but from what i've found out so far is the these 4 drivers check the statis of 4 differant circuits be it milli amps or ohms for stuff like delay head lites, radio when the key is turned off.. I don't want to replace the ecm and not fix the problem, thats a waste of the customers money. He wants to sell this car but it will not pass smog in california because of this stupid code which has nothing to do with smog.any help would be much appeciated