2004 Buick LeSabre+GM-U7

Remote start in this Buick for about a year now and everything worked great. Used the GM-U7 module that did the locks,trunk and the Passkey 3. Now all of a sudden when you remote start the car, it starts and the about three seconds later the security light flashes and the car shuts off. On the module the led light comes on when it goes into remote start so I assume the module is working. I tried another module and the same thing happens. Any ideas on this Passkey system??????