P0120 means Throttle/Pedal Position Sensor/Switch A Circuit. The computer has found a general fault in the throttle or pedal position sensor A circuit. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0120 means
Most vehicles built in the last two decades use electronic throttle control instead of a throttle cable: the accelerator pedal carries two or three position sensors, and the throttle body has a motor and two position sensors of its own. The computer compares the redundant sensors constantly, and any disagreement triggers reduced-power mode as a safety measure. Older engines with a throttle cable control idle with a separate idle air control valve.
P0120 symptoms
- Reduced power or limp mode
- Hesitation or surging
- Erratic idle
- Check engine light
Common causes of P0120
- Failed throttle position sensor
- Wiring or connector fault
- Reference voltage problem
- Throttle body fault on electronic throttles
How to diagnose P0120
- Watch the sensor reading on a scan tool through the full throttle range
- Check reference voltage and ground
- Inspect the connector
Can you drive with P0120?
Use caution; throttle response may be unpredictable.
P0120 tips
On electronic throttles, the throttle body and pedal both have position sensors; read the full code list to see which one is affected.
Will P0120 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0120 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0121 | Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance |
| P0122 | Throttle/Pedal Position Sensor/Switch A Circuit Low Input |
| P0123 | Throttle/Pedal Position Sensor/Switch A Circuit High Input |
Guides that help
When it is more than a sensor
Throttle and idle codes are fixed at the throttle body, the pedal, a sensor or a leak. If those check out and the engine still runs poorly, a compression test separates a control problem from a worn engine; compare engines by code on our engines page.
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