P0123 Throttle Position Sensor/Switch A Circuit High Input: What You Need To Know


Your vehicle is an incredible machine made up of numerous sensors and switches. Each plays a critical role in ensuring that your drive is smooth, safe, and efficient. One such key component is the Throttle Position Sensor. But what happens when something goes wrong with it, like a P0123 error code? Let’s delve into the details.

What is a Throttle Position Sensor?

The Throttle Position Sensor (TPS) is a vital sensor that feeds information to your vehicle’s engine control unit (ECU). It relays data about the position of the throttle in an internal combustion engine, crucial for the proper mixing of air and fuel.

car vertical

Role of the Throttle Position Sensor 

The TPS is key in determining the amount of air entering the engine. As you press or release the accelerator pedal, the TPS sends a corresponding signal to the ECU.

What does the ‘A’ circuit mean?

In the context of the P0123 code, the ‘A’ circuit refers to a particular circuit in the TPS.

Understanding Error Code P0123

P0123 is a generic diagnostic trouble code that indicates a problem with the throttle/pedal position sensor/switch “A” circuit high input.

What does a High Input in the ‘A’ Circuit signify? 

A high input in the ‘A’ circuit means the voltage input to the ECU from the TPS is abnormally high, signaling a potential issue.

Causes of P0123 Error Code

Several issues can trigger the P0123 error code, including a faulty TPS, damaged wiring, or even a faulty ECU.

Symptoms of P0123 Error Code

Common symptoms of the P0123 error code include an unstable engine idle, poor fuel economy, and difficulty in acceleration.

Fixing the P0123 Error Code

Once the issue is diagnosed, it can be resolved by replacing the faulty TPS, repairing or replacing the damaged wiring, or replacing a faulty ECU.

Preventing P0123 Error Code 

Preventing P0123 largely involves regular maintenance of your vehicle, including frequent checks and inspections of the throttle position sensor and associated wiring.


Understanding and resolving the P0123 error code is crucial to maintaining your vehicle’s performance. Always seek professional help if you’re unsure about diagnosing or fixing this issue.


  1. What does P0123 mean in terms of my vehicle’s performance? P0123 indicates a potential issue with your vehicle’s Throttle Position Sensor, which can impact your vehicle’s performance, including unstable idling and poor fuel economy.
  2. Can I drive my car with a P0123 code? While it may not immediately stop your vehicle from running, driving with a P0123 code is not recommended as it could lead to more serious engine issues over time.
  3. How much does it cost to fix a P0123 code? The cost to fix a P0123 code largely depends on the underlying cause. It could range from $50 for a new sensor to several hundred dollars if the ECU needs to be replaced.