Hello and thanks for your question in the autoaid community.
This faultcode means: P0121 - TP Sensor Circuit Insufficient Activity
Look for the Pins and wires at the throttle pedal, maybe there is the fault.
Plug off and on for new contact of the Pins.
When there is no fault shown, look into the is values of the Control unit, there must be shown if there is already activ and correct.