Check engine light on. P2138 code

Hi today i was driving to work and it was raining pretty heavily and when i got to work, EPC light came on. When I turned the car on after work, the check engine light was also on and the car was slowww....I got home, scanned it, got p2138 code. It looks like it might be the gas pedal or throttle body sensor? The throttle body looks brand new, previous owner replaced it. I did an oil change yesterday if it matters. Anyone had similar issue? my audi is 2001 a4.