Have a 1995 Cadillac SLS. Long story but replaced ECM with unit from a car in wrecking yard. Service tech told me before hand that upon plugging in his computer it said that my alternator was problem and reason that car died. Replaced alternator still problem. Replaced ECM and battery still not getting charge after 15 minutes of running it quits charging. Alternator rechecked and it is good. Question is what onboard computer or just what tells the alternator to turn on and start charging and to run the car? Thank you in advance for any ideas.
Have seen these problems all too often and goes back to the fact that many mechanics calling themselves mechanics should not be allowed to touch a car. If you haven't yet burned up the ECM, (again) the problem most likely is a bad body ground in the engine area.
just a couple weeks ago was dealing with a guy that had a new alternator, new ECM, new gauge cluster, and battery put in at different times just like you. The battery was destroyed by a surge as was the gauge unit and ECM. The negative ground to the frame was repositioned a foot and that solved all the problems. $1,300 later the 5 minute fix was the repair.