How much does it cost to fix P0122?

DIY repair typically costs $35–$150 for parts. Professional repair runs $120–$450 including parts and labor.

P0122

Powertrain

Moderate

Throttle/Pedal Position Sensor/Switch A Circuit Low Input

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OBD2 code P0122 indicates that your vehicle's engine control module (ECM) has detected an abnormally low voltage signal from the Throttle Position Sensor (TPS) or Accelerator Pedal Position Sensor Circuit A. The TPS is a critical component that monitors the position of your throttle plate and communicates this information to the ECM, which uses it to calculate proper fuel delivery, ignition timing, and transmission shifting. When the voltage signal falls below the manufacturer's specified minimum threshold (typically below 0.17-0.20 volts), the ECM triggers code P0122 and illuminates the Check Engine Light.

This code matters because your engine relies on accurate throttle position data for optimal performance and fuel efficiency. When the ECM receives incorrect low-voltage readings, it cannot properly manage the air-fuel mixture, which can lead to poor acceleration, stalling, rough idling, and activation of "limp mode"—a protective state that limits engine power to prevent damage. In limp mode, your vehicle may feel sluggish and may not accelerate beyond 2,500-3,000 RPM, making highway driving difficult or unsafe.

If you're experiencing P0122, you should address it within the week. While not typically an emergency that requires immediate towing, driving with this code can cause poor fuel economy, catalytic converter damage from improper combustion, and potentially leave you stranded if the engine stalls at an inopportune time. The most common fix is replacing the throttle position sensor, which costs between $35-150 for DIY repairs or $120-450 at a professional shop. Before replacing parts, inspect the TPS connector for corrosion and check the wiring harness for damage, as these simpler issues account for about 30% of P0122 cases and can often be repaired inexpensively.

Severity

Moderate — Address SoonThis Week

Symptoms

•Check Engine Light illuminated
•Poor acceleration or lack of throttle response
•Engine stalling or rough idle
•Vehicle stuck in limp mode with reduced power
•Erratic or surging idle speed
•Difficulty starting the engine

Likely Causes

Faulty throttle position sensor (TPS)45%

The TPS itself may have failed internally, producing voltage readings below the normal operating range. This is the most common cause of P0122 codes.

Damaged or corroded wiring/connectors in TPS circuit30%

Corroded pins, broken wires, or loose connections can cause low voltage signals to reach the ECM, triggering this code even when the sensor is functioning properly.

Short circuit to ground in TPS wiring harness15%

If the signal wire is shorted to ground anywhere in the harness, it will pull the voltage reading down below specifications, causing the ECM to register a low input fault.

Failed or failing engine control module (ECM)7%

In rare cases, the ECM's internal circuitry for reading TPS signals may malfunction, incorrectly interpreting normal voltage as too low.

Low voltage from vehicle electrical system3%

A failing battery, bad alternator, or poor ground connections can cause insufficient voltage supply to the TPS, resulting in abnormally low signal readings.