“Throttle fault” can refer to the driver’s pedal, the throttle assembly or the information passed between them and the ECU. A shortened code-reader description can blur those distinctions. Start by saving the complete P0121 entry and the engine identification.
Identify the component named by the vehicle
HELLA’s code reference places P0121 in throttle/pedal position circuit plausibility. Its component guide explains that a throttle potentiometer reports opening angle to the engine controller. Code reference and throttle-position explanation.
The actual sensing technology and arrangement vary. The generic wording is not enough to choose a part or a connector pin for testing.
Describe the response precisely
Does the car hesitate, idle poorly, limit power or stop responding to the pedal? Record whether it happens immediately after starting or after warming up. Include any throttle cleaning, replacement, battery disconnection or attempted adaptation in the history.
Garages can help by labelling pedal and throttle readings separately and retaining any requested-versus-observed position data. A screenshot of two percentages without their channel names is hard to assess. State whether the symptom occurred during the recording.
Avoid turning adaptation into a guess
An adaptation procedure should follow the correct vehicle instructions and its prerequisites. Record any failed procedure and its message instead of repeatedly running it. If accelerator response is unpredictable, arrange assistance rather than continuing to drive.
Discuss the findings with AXION. We can agree whether the next step needs the vehicle or whether a supported ECU assessment is appropriate.
Reviewed September 2026. Use the complete manufacturer-specific fault description and vehicle repair information.