Starting Problems

[cangod]

2003 Sierra ... Truck starts and stalls immediately. When I use my command start sometimes the lights blink and horn starts honking, I noticed anti theft light is on.Happens about once a week , any suggestions? was told it might be a problem with command start

[bobcat5544]

The trucks theft detrunt system is shuting down the truck. If the command start is after market then it probaley is the cuase, but I wont rule out the ignition lock cylinder