P0122 Code – Meaning, Causes, Symptoms (& How To Fix)

The Check Engine Light is something that no one likes to see, particularly when it seems the engine performance has been affected. With the P0122 code, you don’t have a lot of possible causes, so it can be easier to troubleshoot. 

This guide will explain the significance of the P0122 code. This guide will also explain the causes and the consequences of the problem, as well as the steps you can take to correct it. 

Definition of Code P0122

P0122 – Throttle Position Sensor/Switch A Circuit Low Input

What does the P0122 code mean?

If the input to your throttle position sensor/switch A circuit is lower than you expected, then this trouble code P0122 will be logged. The PCM is responsible for logging this code when the input doesn’t mean normal parameters. 

It is responsible for determining the position of your throttle. Most configurations have the sensor mounted on the throttle body. A DTC can also be used to indicate that the electronic throttle pedal is not working properly. This sensor is standard on all newer models. 

When the throttle position sensor detects a fuel/air ratio, it sends a signal to the computer. It’s also needed to run the emission system. 

P0122 Trouble Code Symptoms

It is possible for the symptoms to vary depending on what went wrong. The Check Engine Light will come on when the code P0122 is entered, but other symptoms may vary. 

Below are some signs you might be noticing:

RELATED : 5 Signs that a Throttle Position Sensor is Bad (Replacement Cost).

The P0122 Code: Causes

The P0122 code can be set for many reasons. Without a complete diagnosis, it’s difficult to know what’s wrong, which is why you want to follow the steps listed lower below. 

These are some common reasons:

• The throttle position sensor was not calibrated/mounted incorrectly
• Shorted/damaged electrical wiring
• Broken/bad throttle position sensor/switch
• Questions concerning PCM

Is the P0122 Code Really Serious?

Extreme – When the P0122 code sets, the engine’s ECM goes into the failsafe or limp mode. During this time, you won’t have as much control over the vehicle as the speed will be automatically limited. This can cause serious problems if you're driving on the highway.

Additionally, the P0122 DTC could also cause jerking and bucking. All of these are potential hazards, so it’s best to have them fixed. 

How can you fix the code P0122?

You will be able to determine what repairs or replacements are needed after a thorough diagnosis. Although these repairs are most commonly performed, you may need to repair something more. 

• Mount throttle position sensor correctly
• Check the throttle position sensor
• Restore damaged or short-circuit wiring
• Change the switch/torque position sensor.
• Replacing or reprogramming PCM 

Common mistakes in diagnosing P0122

People tend to skip the inspection. It’s common to go ahead and replace the TPS without first ruling out that there’s an issue with its mounting or wiring.

A thorough inspection is always recommended. After that, you will have a better understanding of what’s wrong, so you don’t replace unnecessary parts. 

How to diagnose P0122 Trouble code

Even if you aren’t a professional technician, you can still troubleshoot your issues with the same steps. The following steps are used by most mechanics to troubleshoot the P0122 code. 

1. Check for trouble codes. To see what happens, reset the codes.
2. The throttle position data can be monitored using freeze frame data. If it doesn’t match the specs set out in the service manual, there could be a problem with the sensor or its wiring.
3. Verify all connections and wiring. Verify that your TPS has been properly mounted. Adjust it to ensure proper measurements.
4. The code scanner has the capability to calibrate the throttle position sensor.
5. If the wiring and mounting aren’t to blame, you may need to replace the sensor or switch.
6. These steps are not enough to fix the problem with your PCM. It might be necessary to reprogram the PCM or replace it.

If you can’t figure out what’s causing the problem, it’s always best to consult with a professional mechanic. You don’t want to replace parts that are good. 

The estimated repair cost

After you've completed all the steps of diagnosis, you can get a better understanding of what to do. If you can’t repair the problem yourself, you will need to pay for the parts and labor. Below are some estimates of typical repairs.

• Mount throttle position sensor – $25-$75
• Repair electrical short/damaged wiring – $50-$500
• Replace throttle position sensor/switch – $100-$350
• Reprogram or replace PCM – $250-$2,500

The P0122 Code: Mechanics Tips

There are many other codes that may be present in the car's computer when you get the P0122 error code. Numerous codes could indicate that the throttle position sensor is not working properly in the A-position. These codes can also be seen:

• P0120: Throttle Position Sensor/Switch A Circuit Malfunction – this code shows the voltage rises or drops more than normal or otherwise stutters when compared to the “B” sensor
• P0121: Throttle Position Sensor/Switch A Circuit Range/Performance Problem – this code shows the throttle angle isn’t matching the expected value for the RPMs
• P0123: Throttle Position Sensor/Switch A Circuit High Input – this code suggests that the voltage is exceeding what’s considered normal
• P0124: Throttle Pedal Position Sensor/Switch (TPS) A Circuit Intermittent – this code shows that the sensor is sending erratic or intermittent signals during a certain period