Truck engine shuts off without foot on pedal

Idle air control circuit or valve.

Clean throttle body, the butterfly valve is sticky with build up

I cleaned up the throttle body but the truck won’t crank up now

After cleaning valve, it takes a few cranks to start back up. Depends on how much throttle body cleaner you sprayed down there. Just keep cranking a few times

If this persists you might consider getting error codes from the OBDII port if your 2004 truck has one. (Below the dash.) If it is a throttle valve position detector fault or an accelerator pedal position detector fault the OBDII port can reveal this with its readout error code. Most likely though, the other guys are right about the throttle body cleaning which must be done properly or the crud gets into your intake.