Cadillac Repair: electrical problems, northstar engine, ground circuits

Question
I have a 99 seville v8 northstar engine. Started having all kinds of codes battery not charging ,service air bag,traction control needs service,charging system needs service, checked charging voltage got 15 volts plus door locks dont unlock when put in park also windows wont come down when the car is running, seats stop working also, but sometimes when i start it there are no codes and everything works fine, put a new battery in, no change, as the first code i got was battery not charging. The battery was no good had it checked,thats why i replaced it.Im at a loss can you steer me in the right direction?

Answer
Hi Michael,
 
        Sounds like you might have a ground problem. If anything was worked on in the car recently before this problem started I would definitely check to make sure that everything was tightened up in that area.

        For some reason with the Northstar engine where the negative/black battery cable attaches to the engine on the RF of the block it has a tendency to loosen up and then strange things start to happen. Otherwise you will need to get a wireing diagram and terminal locations and start traceing the ground circuits that are affected. Since I don't have a shop manual available the best I can say is to remove the panels below the steering column and the panel under the dash just in front of the door on the drivers side to see if any of the ground terminals are loose and tighten up and bolts/screws that are and the problem may be fixed. Bill