P2122 Throttle/Pedal Position Sensor/Switch D Circuit Low Input

P2122 means one accelerator-pedal position sensor circuit (sensor D) is reading a voltage below its normal range — the signal has dropped low, pointing at the pedal sensor or its wiring.

Code details

Generic OBD-II · P2

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not overlook the wiring; a chafed harness or corroded connector often causes low-input pedal codes rather than the sensor itself.

Symptoms of P2122

Reduced-power / limp mode.
Poor or non-responsive throttle.
A warning light on the dash.

Common causes of P2122

A failed accelerator-pedal position sensor.
A short-to-ground or open in the signal wire.
A corroded or damaged pedal connector.
A reference-voltage fault.

Useful checks before replacing parts

Back-probe the pedal-sensor D signal and reference voltages.
Inspect the pedal connector and harness for damage or corrosion.
Confirm the sensor sweeps smoothly from rest to full travel.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.