Sorry for my hickology, When the temperature is around 30 degrees, the truck will crank but not start. the security light will flash on and off non stop. When the temperature warms up to 40 degrees or warmer the truck will start as soon as you turn the key. I have already changes out the cylinder head temperature sensor and the ambiant air sensor. Thanks for any help that you can give. I have had the truck hooked up the a Snap-on scanner and the tech said all the sensors were reading correct. No check engine light, no codes.

 

So we are all on the same page , when trying to start the engine we are cranking the engine,
When the engine starts running we generally say it fires up, it starts, or it runs or is running.
If we are trying to start the engine and it has not started to run on it's own , it cranks ,but doesn't start. If it isn't too much trouble could you please redo your question so someone slow like me could get a better idea of what you are asking? Thanks