I have a 2000 Grand Prix GT with 280,000 miles on it. I purchased a wreaked Grand Prix GT with 173,000 miles on it that was wreaked. I swapped the motors out and my 2000 Grand Prix ran fine for two days. I did not change computers but I did change the gauge cluster. It is now sitting in my driveway and turns over and wants to fire and everything but it wont start. I changed the computers thinking it could be that, but nothing. I then unhooked the battery and tried leaving it sit for 10 minutes to try resetting the security system, still nothing. I am currently lost at this point and could use some help. If you have any ideas, please post. Thanks, Brett