I recently swapped out a motor from a 2003 Mustang to a 1999 Mustang. I swapped the entire wiring harness, one piece, for the motor and tranny. I also swapped the harness for the computer and the computer. The car will not start with the new computer even though I swapped out the key. The problem with the old computer was that the temp gauge went backwards and the A/C didn't work. Anyone have any suggestions?