OBD-II Trouble Codes

P0120 Code: Throttle/Pedal Position Sensor “A” Circuit

Reading Time: 3 minutes

Your vehicle’s throttle position (TP) sensors and accelerator pedal position (APP) sensors are crucial to engine operation. Just like any other engine sensor, these sensors may fail due to several reasons. P0120 is an error code that indicates a potential fault with one of your vehicle’s TP/APP sensors or the sensor’s circuit.

What does the P0120 Code Mean?

Diagnostic trouble code (DTC) P0120 stands for “Throttle/Pedal Position Sensor ‘A’ Circuit.” It is triggered once the powertrain control module (PCM) detects abnormal voltage readings from one of your car’s TP or APP sensors. To understand the code better, let us briefly discuss how TP and APP sensors operate.

Note: The definition of Code P0120 may vary depending on the vehicle manufacturer. It is best to consult a repair manual or repair database for the exact code definition.

TP Sensors

A TP sensor measures your throttle blade opening. The number of TP sensors may vary depending on your vehicle’s make and model. For example, older vehicles that have mechanical throttle linkage are equipped with only one TP sensor. On the other hand, vehicles with electronic throttle control (ETC) are equipped with two sensors. Usually, these sensors are located on the throttle body assembly.

The data from your TP sensors is sent to your PCM, which uses the information when adjusting idle speed, fuel delivery, and shift points. On vehicles with ETC, the data is also used for throttle motor/throttle blade control.

Faults in these sensors are serious, particularly for vehicles with ETC, because they may cause the vehicle to go into fail-safe mode. This is a condition where the car’s speed and acceleration are limited to avoid damaging other components.

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Code P0120 may be set when the PCM detects abnormal voltage readings from one of your car’s TP or APP sensors.

APP Sensors

On some vehicles, the P0120 code may indicate problems with one of your car’s APP sensors. In an ETC system, APP sensors are used as a primary input for throttle blade/throttle motor control.

Once the PCM detects a deviation from the expected voltage signals from the APP sensor or TP sensor, it will trigger the code.

What are the Possible Causes of the P0120 Code?

It may be difficult to pinpoint what underlying problem is causing error code P0120. To give you an idea, here are the possible causes of the P0120 code:

  • Faulty throttle position sensor
  • Faulty accelerator position sensor
  • Damaged or corroded wiring or connectors
  • PCM issues, such as software in need of an update
  • Dirty or defective throttle body

What are the Common Symptoms of the P0120 Code?

Code P0120 will most likely trigger the “Check Engine Light.” Aside from that, here are some of the symptoms you should watch for:

  • Engine may misfire
  • Hard Starting (rare cases)
  • Engine may hesitate during acceleration (rare cases)
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An illuminated check engine light is a common symptom of the error code P0120.

How to Diagnose the P0120 Code

Again, the code P0120 is not an issue you can disregard, especially if your vehicle relies on ECT systems. It is best to bring your vehicle to your trusted repair shop for proper diagnosis.

However, if you have advanced auto repair skills, and you would want to diagnose this trouble code yourself, here is a video that can help you understand the code better:

How to Fix the P0120 Code

There is no exact fix for this code. The exact repair procedures will vary depending on your vehicle’s make and model. For example, repair steps for P0120 in a Toyota may vary from P0120 in a Chevy.

If you are not familiar with auto repair, it is best to bring your vehicle to a repair shop. Mechanics would know how to properly diagnose and fix your vehicle.

However, if you have the DIY automotive skills and you’re confident you can fix this code yourself, you can use online repair sources and guides to help you determine what solution is suitable for your vehicle. If you would like, you may also get an ALLDATA single-vehicle subscription.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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