Could be the RS module or anything it depends on to make sure it is safe to RS.

 

Do you have a grey key or a black key. Grey key means you have a factory installed security system that requires a over ride kit. The grey key has a small chip inside that links to the ignition when you start it with the key. Just a thought.

 

This is a factory RS.

From what it sounds like is it's not getting a signal that the truck has started. Sounds like the starter continues to run after the truck starts. Then it shuts the whole thing off and retries. Again not getting a signal that it's started.