Understanding the P0122 Throttle Position Sensor/Switch A Circuit Low Input

Introduction to P0122 Code

Do you know that feeling of dread when your vehicle’s check engine light comes on? It’s like your car is telling you, “Hey, something’s not right here.” But what could it be? One potential culprit could be a P0122 code – a problem with your Throttle Position Sensor (TPS). But what does that mean, and how can you fix it?

What is a Throttle Position Sensor?

Imagine this: You’re a puppet master, and your car is the puppet. Every time you press the gas pedal, you pull a string that controls how much fuel your car uses. This string is, in essence, your Throttle Position Sensor. It’s a critical piece of your engine management system that monitors the air intake of your engine.

How the Throttle Position Sensor Works

Think of the Throttle Position Sensor as the middleman. When you press the gas pedal, it sends a signal to your car’s engine management system, telling it how hard you’re pressing down. This information helps your engine determine the right amount of fuel to inject at any given moment. When this sensor fails or sends incorrect data – which is what the P0122 code indicates – it can create a multitude of problems.

Identifying a P0122 Code

Common Symptoms

How can you tell if you’ve got a P0122 code problem on your hands? There are several telltale signs. Your car might feel like it’s lacking power or having difficulty accelerating. You may notice that your fuel economy isn’t what it used to be. And of course, that dreaded check engine light will likely be on.

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Possible Causes

So, what could be causing a P0122 code? It could be a faulty Throttle Position Sensor, a problem with the sensor’s wiring, or even an issue with the engine control module itself.

Diagnosing and Fixing a P0122 Code

Initial Diagnosis

To confirm that you indeed have a P0122 code problem, you’ll need a device called an OBD-II scanner. This tool will allow you to read the error code from your car’s computer.

Tools You Might Need

Apart from an OBD-II scanner, you might also need a digital multimeter to check the voltage output from the Throttle Position Sensor. Remember, safety first! So, always have your protective equipment on hand, such as gloves and safety glasses.

Step-by-Step Diagnostic Process

First, use your OBD-II scanner to confirm the P0122 code.

After confirming the P0122 code, you’ll want to inspect the Throttle Position Sensor and its wiring visually. Look for any obvious signs of damage or wear. If you don’t see any, you can use your multimeter to check the sensor’s voltage. If the voltage is lower than it should be (hence the “circuit low input” part of the P0122 code), you’ve found your problem.

Fixing the Issue

Once you’ve confirmed that the Throttle Position Sensor is the issue, you can replace it. Depending on your vehicle, this might be a relatively straightforward process, or it could be a bit more complicated. Always consult your vehicle’s service manual for exact procedures.

When to Seek Professional Help

If you’re not comfortable diagnosing or fixing this issue yourself, or if the problem persists after you’ve replaced the sensor, it’s time to seek professional help. A certified mechanic can help you diagnose and fix the problem.

Preventing Future P0122 Codes

Regular Maintenance Tips

One of the best ways to prevent a P0122 code is regular maintenance. This includes routine checks of your vehicle’s electrical system and replacing worn-out components before they cause problems.

Importance of Early Detection

Early detection is crucial when it comes to preventing P0122 and other codes. The sooner you can identify and fix a problem, the less damage it will cause in the long run.


Dealing with a P0122 code might seem intimidating, but it doesn’t have to be. With a bit of knowledge, some basic tools, and a proactive approach to vehicle maintenance, you can ensure that your car stays in tip-top shape.


  1. What does a P0122 code mean? A P0122 code means there’s a problem with the Throttle Position Sensor’s circuit, specifically a low input signal.
  2. Can I drive with a P0122 code? While it might not immediately harm your vehicle, driving with a P0122 code can lead to decreased fuel efficiency and performance. It’s best to address the problem as soon as possible.
  3. What causes a P0122 code? Possible causes include a faulty Throttle Position Sensor, wiring problems, or issues with the engine control module.
  4. How do I fix a P0122 code? Fixing a P0122 code usually involves replacing the Throttle Position Sensor. However, if the sensor isn’t the problem, further diagnosis might be necessary.
  5. Can a P0122 code reappear after it’s been fixed? If the underlying issue causing the P0122 code wasn’t correctly addressed, the code could reappear. Regular maintenance and early detection can help prevent this.