Limp home mode limited throttle P0638 code

The car in question is 2014 hyundai elantra 2.0 litre GDI Engine with push button start system and with automatic transmission. Throttle body has been replaced for this code P0638 but no fixed. Have done 10 seconds key on and key off relearn but the code still pops up. and the car has limited throttle i hav tested wiring to the motor and connectors at the pcm for corrosssion and etc but find nothing. I am going towards pcm any thoughts. Note here i can have the car to drive fine and not set a code when i turn on the key and live it for few seconds(10) but when i turn on the key and immidiately start the car right away, the car will set the code and it will be in a limp home mode. SO i am thinking this is a pcm not able to retain what it learn which is why anytime i turn on the key i need to relarn it again before the code will not set. Simply put every key on, living the car few seconds everything is fine. BUT KEY ON, starting the car right away is when the code will set(P0638) and limited power.

does the ecm open and close the motor when you turn the key on?

what about tps?

unfortantly keep in my you MIGHT have gotten a bad part?

have you "load test" the wiring?

thank you my friend. Pcm was controlling the motor and i have also load tested the wiring.
long story short i replaced the pcm with used one and it fixed the vehicle.
the code did not come back and the car drives fine.

interesting.

you dont have any testing methods for the pcm failure?

or you just replaced it?
i would like to know exactly what signal it wasnt happy with?

congrats on your fix

I think it was a relearn issue. The pcm has to learn the motor but in this case it has failed to learn it. SI says the code can set if relearn is not done and i follow the procedure but it did not learn. but it is fine if you allow the key on for few seconds before starting the engine.