How much does it cost to fix P2122?

DIY repair typically costs $50–$200 for parts. Professional repair runs $150–$500 including parts and labor.

P2122

Powertrain

Moderate

Throttle/Pedal Position Sensor/Switch "D" Circuit Low

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Code P2122 means that the engine's computer has detected an abnormally low voltage from the 'D' circuit of the throttle or accelerator pedal position sensor. Modern drive-by-wire vehicles use sensors in the gas pedal to tell the computer how far you're pressing it. The 'D' circuit is one of two redundant sensor circuits — when its voltage drops below approximately 0.17 volts, the PCM flags this code.

When this code triggers, the vehicle almost always enters limp mode as a safety precaution. You'll find that pressing the gas pedal produces little or no response, and the car may barely creep along. This is the computer protecting you from potential unintended acceleration by essentially ignoring the pedal input when it can't trust the sensor signal.

The most common fix is replacing the accelerator pedal position sensor, which is typically integrated into the pedal assembly itself. Before replacing parts, however, it's worth checking the wiring harness and connector for corrosion or damage — especially the connector at the pedal, which sits in the footwell where it can be exposed to moisture and kicked by occupants. This is generally a straightforward repair for a DIYer with basic tools, as the pedal assembly is accessible and usually held in by a few bolts.

Severity

Moderate — Address SoonThis Week

Symptoms

•Engine enters limp mode with very limited throttle response
•Accelerator pedal feels unresponsive or dead
•Vehicle barely accelerates above idle speed
•Check Engine Light is on
•Engine may stall at idle or low speeds

Likely Causes

Faulty accelerator pedal position sensor40%

The 'D' circuit is typically part of the accelerator pedal position (APP) sensor assembly. Internal wear or failure of this sensor causes it to output a voltage below the PCM's expected minimum threshold, usually under 0.17 volts.

Wiring or connector damage in the pedal circuit30%

Corroded connectors, chafed wires, or a loose harness connection between the pedal sensor and the PCM can create excessive resistance, dropping the signal voltage below the acceptable range.

Poor ground connection20%

A corroded or loose ground wire in the pedal position sensor circuit can cause the signal voltage to read abnormally low, especially in cold or humid conditions where corrosion is accelerated.

PCM internal circuit fault10%

In rare cases the PCM's internal pull-up resistor or analog-to-digital converter for the D circuit may fail, causing it to read an artificially low voltage even when the sensor is functioning correctly.