99 chevy silverado 5.3 Z71 loaded - bought 99 silverado z71 5.3 with an aftermarket auto start already installed. worked fine and still does, however it has recently left me ...

bought 99 silverado z71 5.3 with an aftermarket auto start already installed. worked fine and still does, however it has recently left me stranded a few times when neither the auto start nor the key would start the truck. it turns over and shuts right off.like its the factory security. i do not use the door lock key fob and rarely use the auto start. i have recently installed a plow and a new battery. plow works fine, lights etc. but didnt have an issue with starting until a couple weeks after plow install. ( havent had to use plow yet either. ) key does not open passenger door and driver handle was changed or repaired. key works in driver door. left truck set overnight..started no problem for a couple weeks then did it again. same thing , left it 8 hrs....started fine. Security light comes on and stays on sometimes. any help appreciated. i would not be opposed to eliminating auto start and security altogether . Thank you.

I sounds like you have a problem with the aftermarket parts. Get with the manufacturer of the system and see if you can get a wiring diagram for it. You can then check to see where the problem is.