Hi, bnice; I think I would start by charging and testing the battery, then the charging system. Low voltage can cause all kinds of 'weird' symptoms. Can't remember what is the voltage threshold for the computer, but I think the minimum would be around 9-10V. If the voltage is, say, at the low threshold and you add anymore draw, the computer runs home to mama. Have you tried scanning the PCM for any stored codes?
Ok, so I have a 96 chevy pick up. That has been causing me a few problems lately. (I believe its because the ole lady doesnt know how to drive it) but anywho, I had the transmission rebuilt at the end of July/2018, put a new wire cable on there as a result of the old one being tore up.
Truck ran fine but noticed and very subtle jerk in 1st & 2nd gear after, a long duration running at free way speeds. Still proceeded to drive it regularly and had no problem. But, last week after letting ole lady drive down to the airport to work. She stated to me that the truck was dead and wasn't starting, she tried jumping it and it started immediately. However upon putting in drive, the truck died. Jumped it again, went to put into drive and died again. She also says " there was/is this buzzing/ humming noise coming from down by the pedals. Had my friend/mechanic look at it, he claimed the problem was coming from the brake switch box. He changed the relays. And that stopped the humming noise. (She also felt the need to just tell me that while they were working and trying to figure out the problem, they noticed everytime he pushed on brake pedal, the lights inside the cab would come on as well as back brake lights.)
Apparently he then put it back together. And she got in and drove it home. Now upon entering our humble abode, she threw it in reverse, backed in then went to throw it back in park and it died upon shifting it back into park. So there it sits and remains until I can figure out what the issue. Any help would be extremely appreciative. Thank you for reading. Did not intend for this to be so long but, figured better details, greater chances of success hidden within them.