Q: I have a nostart with codes p0883 and p0700 after engine replacment.

My brother recently got his jeep out of the shop for a engine replacement. after a short drive it shut off and would restart but only stay started for a short time. Originally we had a few code stating we had low voltage. I found that the shop didn't attach the braided ground strap to the firewall. They Also failed to ground the battery the the frame of the vehicle. Instead, they had it grounded to a mounting bolt on the alternator. I fixed these two issues and cleaned up the other grounds while i was at it. This unfortunately didn't fix the issue. It still wont start, and if i manage to get it started it will die out after a few seconds like before. I am also getting different codes now. I have a p0883 and p0700. Not sure where else there could be a problem. What could be throwing these codes and what else do i need to do to get it running?

My car has an automatic transmission.