Hi Everyone,

First time poster here. I uploaded a video for ease but in a nutshell the truck won't start unless the throttle plate is slightly open. Once the plate closes the truck turns off completely. I checked the TPS sensor and it reads perfectly but I don't know how to determine if it's the IAC valve or something else. Please let me know your thoughts on this. Thanks.

 

Getting a P0505 code??? That's IAC circuit. If the check engine lite ISN'T on, could try cleaning the throttle body.... Disconnect the battery, physically remove the throttle body, remove the IAC valve, and clean all the passages. Carb cleaner works pretty good, compressed air doesn't hurt either. Once you have it squeaky clean, reinstall everything, hook the battery back up, turn the ignition to On, (not start), count to 10, THEN start the engine. PCM should figure out idle pretty quick.