P2122 means Throttle/Pedal Position Sensor/Switch D Circuit Low Input. The signal from accelerator pedal position sensor D is lower than possible, usually an open circuit or short to ground. 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 P2122 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.
P2122 symptoms
- Reduced-power mode
- Poor or no throttle response
- Idle only on some vehicles
Common causes of P2122
- Failed accelerator pedal sensor
- Damaged wiring or connector at the pedal
- Shorted 5-volt reference
How to diagnose P2122
- Inspect the pedal connector and wiring
- Check reference voltage and ground
- Watch the sensor signal while pressing the pedal slowly
Can you drive with P2122?
Limited; repair promptly.
P2122 tips
Pedal sensor codes often appear with a matching P2138 correlation code. Because pedal sensors are built into the pedal assembly, a confirmed sensor fault means a new pedal assembly.
Will P2122 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 P2122 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 |
|---|---|
| P2138 | Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation |
| P0641 | Sensor Reference Voltage A Circuit/Open |
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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