P0121: Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance
Do not keep driving
Expect hesitation at particular pedal positions, or a limp mode. Ask for the throttle sweep to be observed on live data — a dead spot is obvious there and invisible to a static test.
What this code means
The throttle position signal is electrically valid but does not behave correctly — it may skip, stick, or fail to agree with the second sensor that most drive-by-wire systems carry for redundancy. Worn resistive tracks inside older potentiometer-type sensors produce a characteristic dead spot at a particular throttle opening, which shows up on live data as a flat step in an otherwise smooth sweep.
Likely causes
Start here
- Faulty throttle position sensor · moderate
- Worn throttle position sensor track · moderate
- Carbon deposits in the throttle body · easy
Less common
- Binding throttle plate or linkage · moderate
- Faulty accelerator pedal position sensor · moderate
- Throttle or pedal relearn procedure not carried out · easy
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
Sign in or create an account to add what you found about P0121.