OBD-II Trouble Codes

P0122 Code: Throttle Position Sensor/Switch A Circuit Low Input

Reading Time: 3 minutes

When the Check Engine Light on your car’s dashboard lights up, it’s time to use a diagnostic scanner to determine what faults triggered the CEL. Typically, there are a variety of diagnostic trouble codes that could potentially be the culprit—and one of them is the P0122 code.

What Does the P0122 Code Mean?

Diagnostic Trouble Code (DTC) P0122 stands for “Throttle Position Sensor/Switch A Circuit Low Input.” The powertrain control module (PCM) logs a P0122 code when the throttle position sensor “A” displays lower voltage than normal.

As its name implies, the throttle position sensor keeps track of the throttle’s position. It is usually located on the throttle body, but this fault can also indicate a problem with the electronic throttle pedal on newer vehicles.

a car's throttle position sensor
The throttle position sensor, which keeps track of the throttle’s position, is usually located on the throttle body,

The signal from the throttle position sensor guides the computer in managing the ratio of air to fuel and the best time to trigger the spark plugs. The data also helps manage other parts of the emission system.

What are the Possible Causes of the P0122 Code?

The voltage of the throttle position sensor can drop below the expected range for several reasons, including the following:

What are the Common Symptoms of the P0122 Code?

As with any engine-related trouble code, the P0122 code will activate the Check Engine Light.

Other symptoms include:

How to Diagnose the P0122 Code

Figuring out exactly what triggered the P0122 code can be tricky. You can leave the job to your mechanic or you can try to do it yourself with the help of a detailed guide.

You can check out the video below to help you understand how to diagnose the code properly:

How to Fix the P0122 Code

The sheer number of possible causes that could trigger the P0122 code means there’s no single way to fix it. Most people leave the job to their mechanics, but you can fix it yourself if you’re confident enough in your automotive DIY skills.

If you’re a beginner, make sure to do your research—and there are plenty of online auto repair resources and guides to help you do that. We also suggest getting an ALLDATA single-vehicle subscription (which would be specific to your vehicle) for this and all future repairs your car may need. Also, do consult your owner’s manual before you begin working on your car.

As mentioned, you won’t find a definitive fix for any code. You’ll have to figure out the underlying cause, then do your research on what fixes have worked to clear the code. Keep in mind that some fixes may only work for certain makes and models, and not for others.

For example, replacing the PCM or VCM and repairing the throttle position sensor are some of the fixes that have been confirmed to work for various model-years of the Chevrolet Blazer. However, they may not work for other vehicles that are displaying the P0122 code.

an automotive throttle body
Code P0122 gets logged when the throttle position sensor “A” displays lower voltage than normal.

Other Notes About P0122

Several OBD-II trouble codes also cover the performance of the throttle position sensor at the “A” position. They are:

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