How to Troubleshoot and Fix a P2122 Code on Your Car

Understanding the P2122 Code

P2122 Code

If you encounter the P2122 code, it means that your vehicle’s system has detected an issue in the Throttle Position Sensor (TPS). The TPS works by determining the position of the throttle valve and sending signals to the Engine Control Module (ECM) about its position.

The P2122 code specifically refers to a problem found on TPS sensor B circuit low. To further break it down, TPS sensor B circuit low pertains to low voltage output from the TPS sensor B. This could be caused by corrosion, damaged wiring, poor connections, or even just a malfunction in the TPS itself.

The TPS has three wires that connect to it, the first one is the 5-volt reference which powers the TPS, the second one is the ground wire, and the third one is the feedback signal wire. The feedback signal wire is the one that is usually faulty when the P2122 code is detected.

A TPS is essential in maintaining your car’s performance because it helps the vehicle operate smoothly, like when you accelerate or decelerate. The low voltage output of the TPS can lead to various engine problems that can seriously affect your driving experience. As soon as you notice the P2122 code, it’s best to address the problem immediately to avoid bigger issues with your vehicle in the long run.

One way to identify the posibles causes of the P2122 code is by checking the engine code reading. This code reader plugs into the vehicle’s onboard computer and provides a snapshot of what’s happening inside your vehicle’s system. It can also help detect where the error is coming from. If it is determined that the TPS sensor ​ needs replacing, then it’s best to have it done by a professional mechanic to ensure proper installation and calibration.

If you are a DIY person, you can also try tightening loose connections to your TPS. In doing so, ensure that you don’t over tighten and that you carefully examine the wiring’s integrity. Also, you may try cleaning the connections with contact cleaner. However, it’s better to have it checked by a professional as they are equipped with the right tools and knowledge in handling engine-related problems, ensuring that your vehicle will work just like new after repairs.

Ignoring the P2122 code can lead to more critical issues, such as engine stalling, decreased fuel economy, and even accidents on the road. As a responsible car owner, it’s important to address any issues with your vehicle consistently. Always take your vehicle to a reliable technician or mechanic that understands your vehicle’s needs, and only trust them to handle any repairs your vehicle might need.

Common Causes of the P2122 Code

car engine

The P2122 code is a trouble code that indicates an issue with your vehicle’s throttle pedal position sensor or the accelerator pedal position sensor. When this code appears, it means that the sensor is sending an incorrect signal to the engine control module. It could result in harsh shifting, poor fuel economy, and a reduction in power. Here are some of the most common causes of the P2122 code in vehicles:

1. Faulty Throttle Pedal Position Sensor

car pedal

The throttle pedal position sensor or TPS is a component that measures the throttle’s position. If it is faulty, it may not give accurate readings, and it may send incorrect signals to the engine control module. A faulty TPS can lead to a slow response to throttle inputs, harsh shifting, and poor fuel efficiency.

2. Faulty Accelerator Pedal Position Sensor

Accelerator Pedal Position Sensor

The accelerator pedal position sensor or APPS is a component that measures the position of the accelerator pedal. If it is faulty, it may send incorrect signals to the engine control module. A faulty APPS could lead to a slow response to throttle inputs, harsh shifting, and poor fuel efficiency.

APPSes often malfunction due to carbon buildup inside the sensor. The carbon buildup occurs due to the accumulation of particles and debris from the air passing through the sensor. To fix this problem, you need to remove the APPS and clean it with an electronic sensor cleaner. If cleaning the sensor is not enough, you need to replace it.

3. Faulty Wiring

faulty wire

The P2122 code may appear due to damages or connections in the wiring between the APPS/TPS and the engine control module. Faulty or damaged wiring can result in false signals or loss of signals to the engine control module, leading to harsh shifting and poor fuel efficiency. You should, therefore, inspect your wiring to check if there is any damage or disconnection.

4. Failed Engine Control Module

Engine control unit

If all the above-mentioned components are functioning properly, the P2122 code may indicate a failed engine control module. The engine control module is responsible for communicating with the TPS and APPS, among other sensors in your vehicle. A failed engine control module could cause various problems, including reduced performance and poor fuel efficiency. If you suspect that your engine control module has failed, you should consult a professional mechanic to diagnose and replace the module.


The P2122 code is an indication that there is an issue with your accelerator pedal position sensor or throttle pedal position sensor. These sensors play a crucial role in regulating the speed and fuel efficiency of your engine. Therefore, it is essential to fix the problem as soon as it arises. The causes of the P2122 code range from faulty sensors to damaged wiring or a failed engine control module. You should, therefore, inspect all the components to determine the issue and take the necessary steps to fix it.

Diagnostic Procedures for P2122 Code

Diagnostic Procedure

If you have experienced difficulties with your vehicle and you have received a P2122 code, don’t worry, it is not the end of the world. This code appears when there is a problem with the throttle/pedal position sensor/switch “D” circuit. In other words, your car’s computer is not receiving the correct data from the sensor when you press the accelerator pedal. It is important to address this issue as soon as possible because it can affect the performance of your vehicle and even cause it to stall. Luckily, there are steps you can take to fix the P2122 code.

Step 1: Check the Throttle/Pedal Position Sensor

Throttle Pedal Position Sensor

The first step to diagnosing and fixing the P2122 code is to check if the throttle/pedal position sensor is working correctly. You can start by using a multimeter to measure the voltage of the sensor. With the ignition switch in the “on” position and the engine off, connect the black probe of the multimeter to a good ground point and the red probe to the sensor output wire. The voltage measured should change smoothly as you press the accelerator pedal. If the voltage reading is erratic or stays the same regardless of the pedal position, then the sensor is faulty and needs to be replaced.

Step 2: Check the Pedal and Wiring

Pedal and Wiring

If the throttle/pedal position sensor is working correctly, then the next step is to check the pedal and its wiring. Start by inspecting the pedal and its connection to the sensor. Make sure that the pedal moves freely and that there are no obstructions or damage to the physical components. If everything looks okay, then you can move on to checking the wiring. Disconnect the sensor from the vehicle’s wiring and use a voltage tester to check for continuity between the sensor pins and the engine control module. Make sure that the wiring is not shorted or open and that there are no loose connections.

Step 3: Reset the Error Code

Reset Error Code

After addressing any issues with the throttle/pedal position sensor and wiring, you can reset the P2122 error code. You can do this by disconnecting the negative battery terminal and waiting for a few minutes before reconnecting it. This will clear any stored error codes in the vehicle’s computer. Alternatively, you can use a code reader or diagnostic tool to reset the code.

In conclusion, fixing the P2122 code requires a thorough diagnostic process that involves checking the throttle/pedal position sensor, inspecting the pedal and its wiring, and resetting the error code. If you have any doubts or concerns about your abilities to perform these steps, it is recommended to seek the assistance of a professional mechanic.

How to Fix P2122 Code: Step-by-Step Guide

car engine under repair

If you have encountered a P2122 code on your car’s onboard diagnostic (OBD) system, it means that there is an issue with the signal coming from the accelerator pedal position (APP) sensor. Specifically, the voltage of the signal is too low, indicating a potential problem with the sensor circuit. This article will guide you through the steps on how to fix P2122 code, so you can resolve the issue and get your car running smoothly again.

Here is a step-by-step guide on how to fix P2122 code:

Step 1: Check the APP sensor wiring
The first thing you need to do is to check the wiring of the APP sensor. Look for any visible damages, such as frayed wires or disconnected connections. If you find any issues with the wiring, repair or replace the damaged parts accordingly. Make sure to disconnect the battery before you start working on the wiring.

Step 2: Inspect the APP sensor
If the wiring seems to be in good condition, you need to inspect the APP sensor itself. Check for any visible signs of damage or corrosion on the sensor. Use a multimeter to test the resistance and voltage of the sensor, as per your car’s manual. If the sensor appears to be faulty, replace it with a new one.

Step 3: Check the throttle body
Sometimes, issues with the APP sensor may also be caused by a malfunctioning throttle body. Use a scan tool to check for any error codes related to the throttle body, and look for any visible signs of wear or damage. If you find any issues with the throttle body, replace it with a new one.

Step 4: Reconnect the battery and test drive
Once you have checked and fixed any issues with the wiring, the APP sensor, and the throttle body, it’s time to reconnect the battery and test drive your car. Check for any remaining error codes on the OBD system, and make sure that your car is running smoothly. If everything looks good, you have successfully fixed the P2122 code.

In summary, fixing the P2122 code involves checking the wiring of the APP sensor, inspecting the sensor itself, checking the throttle body, and testing the car after the repairs. While the process may seem daunting, it is manageable for those with some basic experience in car repairs. If you’re not confident in your skills, it’s best to take your car to a trusted mechanic for professional help.

By following the steps outlined in this guide, you can fix the P2122 code on your car and ensure that it runs smoothly. Remember to take all necessary safety precautions when working on your car, disconnecting the battery when necessary, and following the instructions in your car’s manual. Good luck!

Preventing P2122 Code from Appearing Again

car engine check light

Fixing P2122 Code is one thing, preventing it from appearing again is another. Once you have resolved the P2122 error code, there are a few things you can do to prevent it from coming back. In this section, we will discuss some steps you can take to prevent the P2122 error code from appearing again.

1. Regular Maintenance

car maintenance

The best way to prevent any error code from appearing in your car is to keep up with the regular maintenance schedule. Following the manufacturer’s recommended maintenance schedule can help you avoid most car problems, including the P2122 error code.

Regular maintenance includes the following:

  • Regular oil changes
  • Air filter replacement
  • Spark plug replacement
  • Fuel filter replacement
  • Transmission fluid replacement
  • Timing belt replacement

It’s also important to have your car inspected regularly by a qualified mechanic. Regular inspections can help detect potential problems early, allowing you to fix them before they turn into major issues.

2. Check Wiring and Connectors

auto electrical wires

A common cause of the P2122 error code is damaged or loose wiring and connectors. Checking the wiring and connectors frequently and fixing any damage or loose connections can help prevent the P2122 code from appearing again.

You can do this by:

  • Visually inspecting the connectors for any dirt or damage.
  • Removing and reinstalling the connectors to make sure they are secure.
  • Checking the wiring for any signs of damage or corrosion.
  • Repairing or replacing any damaged wiring or connectors.

3. Drive Responsibly

driving responsibly

The way you drive can also affect your car’s performance and the likelihood of error codes appearing. Driving responsibly can help prevent potential problems with your car and keep the P2122 error code at bay.

Here are a few tips for responsible driving:

  • Never exceed the speed limit.
  • Avoid sudden acceleration or braking.
  • Avoid overloading your car with heavy items.
  • Use good quality fuel and keep the tank at least half full.
  • Avoid driving in extreme weather conditions, if possible.

4. Keep Your Gas Cap Tight

gas cap fixed

A loose or damaged gas cap is another common cause of the P2122 error code. Make sure your gas cap is tight after filling up the tank. If your gas cap is damaged, replace it with a new one.

5. Use High-Quality Parts

high-quality car parts

Using high-quality parts is important to prevent the P2122 error code from appearing again in the future. Cheap or low-quality parts can cause more harm than good and lead to other issues with your car.

When replacing parts, make sure you use high-quality OEM (original equipment manufacturer) parts or parts that meet OEM specifications. These parts are designed to work specifically with your car and are more reliable than aftermarket parts.

Following these steps can help prevent the P2122 error code from appearing again in your car. Regular maintenance, checking wiring and connectors, responsible driving, keeping your gas cap tight, and using high-quality parts can all contribute to a better-performing car with fewer error codes.

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