P0120: Throttle/Pedal Position Sensor/Switch A Circuit
Do not keep driving
Expect severely reduced power or a limp mode. Do not plan a long journey on this code — the failure mode is a car that will not accelerate when asked.
What this code means
A circuit fault in the primary throttle or accelerator pedal position sensor. On drive-by-wire vehicles there is no cable between pedal and throttle, so this signal is the only thing telling the engine what the driver wants. Losing it is treated as a safety matter: the module falls back to a redundant sensor if one is available, and otherwise drops to a limp mode that holds the throttle near idle regardless of pedal input.
Likely causes
Start here
- Faulty throttle position sensor · moderate
- Faulty accelerator pedal position sensor · moderate
- Corroded or loose connector · easy
Less common
- Failed sensor reference voltage supply · moderate
- Open circuit in sensor wiring · moderate
Rare
- Failed control module · specialist
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
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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.
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