P2128 means Throttle/Pedal Position Sensor/Switch E Circuit High Input. The accelerator pedal position sensor E circuit, one of the sensors in the gas pedal assembly, is reading higher voltage than expected. 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 P2128 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.
P2128 symptoms
- Reduced power or limp mode
- Engine only idles on some vehicles
- Check engine light
Common causes of P2128
- Open ground or signal circuit
- Signal shorted to voltage
- Failed pedal assembly
How to diagnose P2128
- Compare the pedal sensor readings on a scan tool as you press the pedal
- Check the pedal connector for damage
- Check reference voltage and ground
Can you drive with P2128?
Use caution; throttle response may be limited.
P2128 tips
Pedal sensor codes often come with D/E correlation codes; the fix is usually the pedal assembly or its wiring rather than the throttle body.
Will P2128 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 P2128 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 |
|---|---|
| P2122 | Throttle/Pedal Position Sensor/Switch D Circuit Low Input |
| P2138 | Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation |
| P2127 | Throttle/Pedal Position Sensor/Switch E Circuit Low 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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