Accelerator pedal has to be pressed down to make car move

Question

Has happened twice. Check Engine light came on and the accelerator had to be pressed way down to move.

First time it happened in extreme cold condition and immediately on ignition. Took to the dealer while the check engine light was on. They reported ECM has to be replaced. The check engine light was off when I picked it up and it drove fine for about a week.

Second time it happened while driving in rainy conditions. Next morning Check Engine light was off. The accelerator worked fine. The code read by auto mechanic was for throttle position sensor. P2118 or P2121. Mechanic says if it happens again will replace throttle position sensor.

Please advise.