P0122 Code: Throttle Position Sensor Low Input — Causes, Symptoms and How to Fix

The P0122 trouble code indicates that the engine control module (ECM) has detected a low voltage signal from the Throttle Position Sensor (TPS).

The TPS monitors the position of the throttle plate and tells the engine computer how much the driver is pressing the accelerator.

When the signal voltage drops below the expected range, the ECU stores the code:

P0122 — Throttle Position Sensor Circuit Low Input.

This issue can affect engine performance, throttle response, and acceleration.

🔎 What Does Code P0122 Mean?

Modern vehicles use an electronic throttle control system to manage airflow into the engine.

The Throttle Position Sensor (TPS) measures the angle of the throttle plate and sends voltage signals to the ECU.

Typical TPS voltage range:

• 0.5V at idle

• 4.5V at full throttle

If the ECU detects a voltage that is too low or outside the normal range, it triggers the P0122 code.

⚠️ Common Symptoms of P0122

Drivers may notice several symptoms when this code appears.

Typical symptoms include:

• Check Engine Light

• poor throttle response

• hesitation during acceleration

• reduced engine power

• engine stalling in some cases

• vehicle entering limp mode

In some vehicles, the car may accelerate very slowly or not respond properly to the gas pedal.

🔧 Most Common Causes of P0122

Several issues can trigger the P0122 code.

1️⃣ Faulty Throttle Position Sensor

The TPS may wear out over time or fail due to internal electrical problems.

This is the most common cause of the P0122 code.

2️⃣ Damaged Wiring or Connector

Broken wires or corroded connectors can reduce voltage in the TPS circuit.

This may cause the ECU to detect a low input signal.

3️⃣ Dirty Throttle Body

Carbon buildup inside the throttle body can interfere with the throttle plate movement and affect TPS readings.

4️⃣ Faulty Electronic Throttle Body

In some vehicles the TPS is integrated into the electronic throttle body assembly.

If the throttle motor or sensor fails, the entire throttle body may need replacement.

💰 P0122 Repair Cost

Repair costs depend on the cause of the problem.

Typical repair costs include:

In many cases, simply cleaning the throttle body or replacing the TPS sensor fixes the issue.

🚗 Can You Drive With Code P0122?

The vehicle may still be drivable, but it is not recommended to ignore the problem.

Driving with a faulty TPS can cause:

⚠ poor acceleration
⚠ unstable engine performance
⚠ sudden loss of power
⚠ limp mode activation

It’s best to diagnose and repair the issue as soon as possible.

🔎 How Mechanics Diagnose P0122

Professional diagnosis usually includes:

✔ scanning live TPS voltage data
✔ inspecting wiring and connectors
✔ testing TPS voltage with a multimeter
✔ inspecting throttle body operation

Sometimes mechanics also perform a throttle body relearn procedure after replacing the sensor.

🏁 Final Thoughts

The P0122 code indicates a low input signal from the throttle position sensor.

Common causes include:

• faulty TPS sensor

• wiring problems

• dirty throttle body

• faulty electronic throttle body

Fortunately, the issue is usually relatively easy and inexpensive to repair when diagnosed early.

Fixing the problem quickly can restore proper throttle response and engine performance.