Code P2101 - Throttle Actuator Motor

Check engine code was P2101. Car would have instances of no throttle while driving. Consequently I replaced the Throttle motor with a new motor. I am not sure if I needed to do a complete relearn procedure. Nevertheless I performed three relearn procedures I found on the web after I installed the throttle motor. The car ran flawlessly. However, after driving some 50 miles, the car again had no throttle. I turned it off, and started it and it was good again.

I have Two questions. (1) Is and was a relearn procedure necessary after installing a new motor. (2) If a relearn procedure is necessary, what is the correct and proper procedure?

Thanks for any help you may offer! John