I have a 2008 Tahoe LS with factory remote start. It will not start after vehicle has sat for any period of time. No active CE lights. If I insert the key and turn to the on position then remove the key and engage the remote starter it will work. I do have an aftermarket radio in my truck. I put the Tech 2 on the truck and I do get a U0184 associated with the radio but nothing else. Has anyone seen this before? Ideas?

 

I would clean the connectors on the related modules as possibly power or serial data is getting lost. '08 to '12 GM vehicles had lots of fretting corrosion issues in module connectors so I myself would use a good electronic cleaner / lube and go from there.
Lots of complex issues like are doors being locked being sensed, trans in park, lots of parameters the system looks at.

 

Suggest you have someone with a capable scan tool run a health check on the modules in the vehicle which includes the radio.
Depending on what result is obtained , we go from there..