P2120 Code: Throttle Position Sensor/Switch C Circuit Malfunction

What Does a P2120 Code Mean?

Diagnostic trouble code (DTC) P2120 stands for “Throttle Position Sensor/Switch C Circuit Malfunction.” The TPS is a potentiometer located on the throttle body. It detects the angle of the throttle blade. The TPS sends a signal to the PCM (powertrain control module) as the throttle blade moves.

P2120 is set when the PCM detects a voltage that is outside of its normal operating range. The letter “D” denotes a specific circuit, sensor, or area of a specific circuit.

More on Throttle Position Sensors

A typical throttle position sensor usually has three wires. These include a 5-volt reference feed wire that sends a message from the computer, a signal return, and a voltage signal wire. As the throttle opens, the voltage sent to the PCM varies.

If you’re planning to diagnose or fix code P2120 yourself, you can read our advanced technical discussion about throttle position sensors for more useful information. A better understanding of the electronic throttle control (ETC) system can also help you find the best way to approach the issue.

Note: The definition of the P2120 code can be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What Are the Common Causes of a P2120 Code?

• Sticking throttle return spring
• MAP or TPS connector issues
• Misrouted harness
• Malfunctioning TPS or PCM

What Are the Common Symptoms of the P2120 Code?

• Illuminated check engine light
• Engine misfires when idle or at highway speed
• Issues with idling and stalling

How to Diagnose the P2120 Code

Even though DTC P2120 is a generic trouble code, there isn’t a universal fix for it. Depending on the make and model of the vehicle, several diagnostic procedures may be required.

In addition to a scan tool, you’ll need particular tools and technical details about your throttle position sensor. You should leave vehicle repair and diagnosis to a reliable mechanic if you lack experience in these areas. Otherwise, you can go ahead and identify the problem’s root cause on your own.

How to Fix the P2120 Code

It can be challenging to clear the P2120 error code, particularly if you don’t have the required DIY and automotive expertise. If that’s the case, it’s better to bring your car to a shop for repairs so that an expert can handle the situation.

If, however, you’re certain that you can erase the error code by yourself, make sure you have the appropriate repair manual close at hand before beginning. Check out vehicle-specific guides from resources like Chilton or an ALLDATA subscription, if you haven’t already.