Code Definition

P0122 — Throttle / Pedal Position Sensor / Switch A Circuit Low Input

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0122

P0122 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0122 is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0122 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The throttle or pedal position sensor A is a potentiometer or hall effect device supplied with a 5V reference from the ECM, returning a signal voltage proportional to throttle plate or accelerator pedal position. P0122 sets when the ECM measures sensor A signal voltage below the minimum threshold for a calibrated period, typically under around 0.2V, which is lower than the sensor can legitimately produce even at fully closed throttle. The realistic causes are a signal wire shorted to ground, a lost or collapsed 5V reference supply, an internally failed sensor, or contamination bridging the con...

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