Jump Starter Relay, Starts then Dies. Can't Start Otherwise.
This will be long, but please bear with me. My son's 2007 Cobalt LT 2.2 blew its head head gasket, got hot, junked engine. Found a complete donor car, 2006 Cobalt. I know that the engines are different but replaced the engine, all harness's and computers from donor car.
OBD says no communication, car won't crank. I can get it to crank and run for about 5 seconds by removing the crank relay and jumping the terminals. Gauges don't register and the DIC says power steering and air bag. I have the 5v reference. i think i have checked everything I can find online, but sure I am missing something.
Any help would be greatly appreciated! I'm sure, or at least hopeful, that it is something simple I am overlooking.