2004 tahoe alarm loses programming

I have a 2004 tahoe Z71. Just took delivery last week. Been back to the shop 3 times. They are telling me that the keys have lost their programming. The truck will start and run great for 3-4 times. Then the next time out it will turn over but not fire. Got it back today and they said they have it fixed. Took it out and went to 2 stops. 3rd stop it started but the alarm pad lock with the little car light stayed on. We went immediately back to the dealer.   It's a fine truck. The keys do not have a chip so they can't lose the programming. The Carfax they finally gave my says there was an aftermarket alarm removed and a wiring harness replaced. What to do?

there's no programming for those keys to lose. might want to take it to somebody competant.... but if you want to know what to do when it just cranks on you leave the key in the run position for 15 minutes then turn the key back and start it. that's likely all the morons have been doing, and not actually looked into the problem. dealerships aren't exactly the best at troubleshooting. they'll likely just throw parts at it until it's fixed. possibly at you expense...A DMM is a beautiful thing.

MECP Advanced Installer Certified.

Thank you for the help. I found the service manager and advised that they were about to get a truck back that I really, really liked but I'm not going to have my wife stranded because they continue to kick the can down the road. I'll get it back tomorrow, then we'll see