How to Troubleshoot & Fix P0123 Jeep DTC Code? (Detailed Guide)

The PCM in the jeep constantly monitors the vehicle for any signs of errors. When it detects something wrong, it turns on the check engine light and stores the code.

The P0123 code on the jeep is such an OBD-II code. It indicates a problem with the throttle position sensor or the switch A circuit High input. In this guide, you will find all the intricate details regarding the P0123 jeep code. 

What Does P0123 Jeep Code Mean?

P0123 jeep code means Throttle Position Sensor or Switch A Circuit High Input. When the voltage in the TPS(throttle position sensor) is more than the upper limit of 4.5 volts for longer than two seconds, the P0123 jeep code appears. 

This is the result of the TPS sensor failure or short. The throttle position sensor evaluates the throttle position or opening angle of the throttle blade. It changes the resistance according to these angles. 

This sensor determines the position of the valve and returns a voltage according to the calculated angle. The sensor is mounted to the shaft and throttle body. It is a resistor that has three terminals.

The TPS sensor first analyzes the throttle valve position. On a closed position of this valve, the sensor will return a voltage of 4.5 volts to the PCM. 

In an open position, the returning signal of the sensor will be 5 volts. However, when the TPS detects a voltage that is higher than this upper limit for more than 2 seconds, code P0123 shows up.

The breakdown of code P0123 is-

• P = Powertrain, the system of components that propels the car forward
• 0 = A generic number derived from the SAE standard
• 1 = Malfunction of the TPS sensor
• 23 = Throttle Position Sensor/Switch A Circuit High Input

P0123 Code: What Causes Throttle Position Sensor or Switch a Circuit High Input on Jeep?

The first and foremost step of dealing with code P0123 is knowing what causes the code to appear. 

There are a few select reasons for this code showing up on your jeep unannounced that are easy to deal with. 

Here are the causes of Throttle Position Sensor or Switch A Circuit High Input sent to the PCM-

1. Defective throttle position sensor
2. Wiring issues in the TPS sensor connection
3. Dirty or contaminated throttle body
4. Improperly mounted TPS sensor
5. Faulty accelerator pedal position sensor.

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How to Troubleshoot & Fix P0123 Jeep Code?

In order to troubleshoot and fix the P0123 jeep code, you’ll need to inspect the parts that are likely to cause this issue. 

Check the TPS sensor, throttle body, pedal position sensor, and connections to diagnose the exact source of the problem. Then you can fix the problems accordingly. 

1. Check the Functionality of the Throttle Position Sensor

Most of the time, the main culprit behind the code P0123 happens to be the TPS sensor itself. If the throttle position sensor is defective in some way, it will not correctly determine the amount of fuel the jeep needs. 

Even when the airflow in the system increases, the engine will run with difficulty.

This defective TPS sensor will return a higher-than-usual voltage to the PCM. It will let the onboard computer know about the faulty TPS sensor and summon code p123.

You will need to test the TPS sensor for a proper diagnosis following these steps-

• Use a multimeter to take the readings of the signals in the TPS sensor wires.
• Connect the multimeter between the ground and signal wires of the TPS sensor.
• Press on the accelerator steadily and watch if the voltage keeps increasing without interruption. 
• Repeat the same while releasing the accelerator slowly once again.

If the voltage change is not smooth during the testing process, it means there are dead spots present within the TPS sensor. 

That is a sign of a defective TPS sensor. So, replace the sensor with a new one following the manufacturer’s instructions.

• Disconnect the wiring harness connector from the sensor.
• Remove the TPS sensor from the throttle body by unscrewing it.
• Install the new throttle position sensor in its place.
• Reconnect the wires with the wiring harness connector and TPS.

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2. Inspect the Wiring Connections to the TPS Sensor

Apart from the normal wiring connections, TPS consists of three major wires. These wires connect between the TPS and PCM to send these signals-

1. 5 volts from the PCM to TPS
2. The return signal from the TPS to the PCM
3. Ground from the PCM to the TPS

Any of these wires becoming loose or corroded will definitely get in the way of the return signal. 

Moreover, the wires in the system circuit can also get shorted. Due to this, the returning voltage becomes higher than the operational voltage.

Inspect every one of the wires in the circuit. Check for shorted wires and replace them accordingly. 

Secure any loose connections between the PCM and TPS. If you find corrosion on any wires, try to remove it by using baking soda and water solution. Otherwise, replace the affected wires.

3. Check for Improper Mounting of the TPS Sensor

This problem usually occurs after replacing a TPS sensor. It might occur when the throttle position sensor is not mounted properly between the throttle body and the shaft. 

Without proper installation and mounting of the sensor, it will show some errors which will lead to the code P0123.

Check the TPS sensor to verify whether or not it is properly mounted in its place. You can get the instructor manual to match the exact position of the sensor. 

If it is out of place, remove the sensor and install it according to the manual in the correct way.

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4. Examine the Accelerator Pedal Sensor

The Throttle position sensor works alongside the accelerator pedal sensor to send proper signals to the PCM of the jeep. 

It analyzes and tracks the movement and angle of the throttle valve just as TPS does. This sensor is not present in every single automobile vehicle.

When this sensor is present, it works in tandem with the TPS. Therefore, if there is anything wrong with this particular sensor, the signals are not transmitted correctly. 

As a result, the PCM receives a higher incorrect voltage and the code P0123 shows up.

To diagnose this sensor, fully press down on the accelerator and monitor the voltage in the sensor. 

If the values don’t match the supposed voltages, you will need to reset the sensor. Reset the sensor following these steps-

• Disconnect and reconnect the jeep battery once.
• Turn the ignition on.
• Press down on the accelerator and then release it once.
• Turn the ignition off to complete resetting the sensor.

5. Look for Dirt on the Throttle Body

The TPS sensor is mounted just on the throttle body. Over time, dirt accumulates on top of this throttle body. 

This dirt makes the speed of the jeep fluctuate due to the prevention of proper airflow. The air becomes extremely turbulent resulting in a high idle of the jeep.

Upon accelerating, there is a higher input of air in the engine because of the dirty throttle body. 

As a result, the PCM also receives a higher output signal from the throttle position sensor. 

All you need to do to fix this is to clean the throttle body. You can easily get a throttle body cleaner from any auto shop at a cheap price. 

Spray a WD40 cleaner on top of the throttle body and wipe it off with a soft cloth. Repeat this process until it is completely clean and then dry off the solvent from the body.

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FAQs.

In this section, you will find answers to some of the most asked questions regarding the code P0123 on the jeep.

Conclusion

Ignoring the P0123 jeep code might result in becoming a serious problem over the course of time. The sooner you resolve and clear the code, the better your driving experience will be. 

For replacing the TPS or accelerator pedal sensor, feel free to consult an expert if you don’t have any experience in handling these.

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