P0123 – Has Your Throttle Position Sensor Gone Awry?

Have you gotten a check engine light and you diagnosed a P0123 code on your car? Well, that’s really unfortunate. But you should not worry because we are here to help you solve your problem quickly and effectively without any major hassles.

Having a problem like this with the check engine light can be a really frustrating thing to deal with. Why I’m saying this? Well, this is true because you never know what this light means in the first place and how you can overcome this problem.

Especially beginners who don’t even know what trouble codes are and what they mean. So, this is why you need to upgrade your knowledge to a different level and learn how to tackle these issues at home using diagnostic tools and as we said, we are going to help you out with that.

First, we will introduce you to car diagnostics and learn more about the basic stuff. Then we will move on and cover what is a throttle position sensor and the throttle position sensor diagram. After that, we will jump to the problem, which is the P0123 code on your car, and then we will look at the causes, symptoms, and how to diagnose and fix this problem quickly and effectively. So, if you want to learn more, follow along.

P0123 Code

Now before we dive into more complex topics and understand more about the P0123 code. Let’s first cover some of the basics. And that is the topic of car diagnostics for beginners. We decided to cover the basics because there are a ton of people who are reading this article and are not quite familiar with how this procedure is done, so this chapter is dedicated to them.

Nevertheless, modern car diagnostics is a complete science and is a really complex topic that knows to confuse a ton of people out there and make them regret that they started this journey. But you shouldn’t be one of these guys. You need to be persistent because persistence is key when it comes to diagnosing problems with your car.

What is worth noting is that modern cars implement a ton of sensors, modules, and other complex stuff. This stuff cannot be diagnosed like back in the good old days based on the symptoms. In most cases with modern cars, you will need to perform computer diagnostics.

Computer diagnostics is essential if you want to sort a problem that is connected to some of the electrical components. For this, you will need a tool that is known as an OBD2 scanner. With this tool, you will be able to access the PCM. The PCM is also known as the car computer.

This computer runs the car and stores all the fault codes. Like in our example with the P0123 Jeep. Whenever you have a problem with some component, the computer will store the code and will show the check engine light. Then you move on to diagnosing the P0123 Dodge and testing the components with a multimeter.

Throttle Pedal Position Sensor Switch A Circuit Low

Now let’s discuss the problem, which is the P0123 code. What is this code and why does it appear in the first place on your car?

Well, the P0123 code is a generic DTC code that appears on a ton of cars. It doesn’t matter that you have a Jeep, Nissan, Dodge, or even Honda. It will still appear when some conditions are met. So, this means that it is not a manufacturer-specific code and all vehicles that are produced after 1996 could develop this code. But what this code means?

The basic definition for this code is “P0123 Throttle/Pedal Position Sensor “A” Circuit High”. But what does this means in the first place?

Well, this means that the TPS sensor on your car has a high voltage in the A circuit. Inside the sensor, there is circuit A which is the 5 volt supply wire, Circuit B which is the signal wire, and Circuit C which is the ground wire. We are going to explain the diagram more in-depth later on. But what is important for you right now is to know that you have a problem with one of these wires.

There could be multiple causes for this problem and unfortunately, we cannot decide what could be the exact cause unless the sensor is removed and tested. But more on the causes and symptoms, we will elaborate on later in this article.

What is important for you is to learn more about this TPS sensor and understand its basic function and how it is working. And luckily for you in the following chapter, we are going to explain more about this in-depth where we will learn all of the basics when it comes to the TPS sensor so you sort this problem with the P0123 Honda code in no time.

Throttle Pedal Position Sensor Switch

Now we want to cover another really important topic when it comes to the P0123 code. And that is what is a TPS sensor in general. This is really important to understand in order to understand the problem and how to solve it. So, let’s get into it.

The first thing for you to know is that this sensor is integrated into the throttle body in some cases. While in other cases it could be removed from the throttle body and replaced. But what is the purpose of this sensor?

Well, this sensor has a single purpose and that is to track the position of the throttle body butterfly flap. This is the flap that opens and closes. It opens to allow air to enter the combustion chamber and make you go faster. And closes in order so the engine reduces the RPMs and comes to the idle RPM which is at about 800 RPM.

So, as you press on the gas pedal the potentiometer inside of the TPS sensor moves and the voltage increases. So, the computer knows how much the flap has opened and how much fuel to add to the mix so you have a good air to fuel ratio.

What is worth noting is that this sensor works along with the accelerator pedal position sensor, also known as a throttle pedal position switch. This is a drive-by wire system so the computer needs the input from the throttle body as well as the gas pedal. So, the TPS sensor is located on the throttle body as we noted, while the APPS sensor is mounted on the gas pedal in most cars. And both can trigger this P0123 code. Even though the TPS sensor usually is causing it.

Throttle Position Sensor Diagram

Now let’s discuss more about the throttle position sensor diagram. Knowing the diagram will be really useful when it comes to tackling this problem with the P0123 code on your car.

As we said, this throttle position sensor has a simple diagram. Inside the sensor, there is a potentiometer that moves from a closed to a completely open position. This means that from zero the needle of the potentiometer travels to the maximum which is the 5V mark.

There are basically three wires. So, the first circuit is circuit A which is the 5 volt supply, then there is circuit B which is the signal wire that goes to the PCM and the last one is circuit C, which is the ground wire.

The voltage of this sensor moves based on the position of the butterfly flap inside of the throttle body. So, if it is in a fully open position the sensor will produce about 5V. If it goes above this then you get the P0123 code. And more on this we are going to elaborate on when we are going to diagnose this problem with your car. Now let’s cover the main causes of this issue.

P0123 Code Causes

Now let’s cover the most common causes of this problem with the P0123 code on your car. As we mentioned, this is a generic code which means that will affect all of the cars that are produced after 1996.

It is worth noting that there are a number of causes for this problem and it is worth elaborating on them in the following chapters. So, if you want to learn, follow along.

1. Bad TPS Sensor

The first cause for the P0123 code that we would like to cover is the problem with the TPS sensor. This sensor can fail completely and cause you a problem like this on some occasions.

Which in this case shows high input on circuit A. And this is mainly an electrical problem with the sensor itself. Probably the sensor is malfunctioning. What is worth noting is that whenever this sensor is completely dead it will not produce any reading.

And in our case, this sensor is producing a reading and is reporting something. And the next reasons are probably more probable when it comes to a code P0123 code.

2. Short In The Circuit Of The TPS Sensor

The second quite most common cause for the P0123 code is a malfunction of the TPS sensor. The internals of this sensor can fail and start to malfunction.

More precisely a short can happen and you can experience a Circuit A High Input problem with your sensor.

What is useful in these situations is to back probe this sensor and learn more about the voltage is producing. If this is the case, the voltage should be more than 5V because of a defect. But still, it’s the same as the case when the sensor is dead. Repairing this sensor is close to impossible and replacement will be necessary if you want to fix the P0123 Honda code on your car or truck.

3. Short In The Wiring From The Harness To The Sensor

The next very common cause for this problem with the P0123 code is a problem with the wiring of the car.

We love to park our cars in barns or under trees where there are rodents that love to make nests. So, it can happen for them to get inside of your engine bay and chew up some of the wirings.

This is a really common occurrence for a lot of people. So, you really need to check the harness and see its condition of it.

Also, if you like to wash the engine, you might have caused corrosion to some of the wirings. This is why we do not recommend washing engines with water hoses and high-pressure washers. It might not be an instant problem. But after a few days when the rust will start to creep up, it could become a problem. So, beware of this.

Also, check the connector and make sure that the connections are good and clean. If there is rust, clean the rust and make sure that the contact is good and the wiring is not loose.

4. Dirty Throttle Body

The next probable cause for this problem with the P0123 code is an issue with the throttle body itself.

The throttle body basically is the component on which this sensor is located. And this throttle body can get clogged up with carbon deposits and stay open in some cases.

Whenever the throttle body stays open, it means that the sensor is generating higher input. So, it could easily trigger the P0123 code.

Your best bet would be to check the condition of this throttle body and see if the flap works as it should. If the flap is stuck open at some point, here lies your problem.

You need to clean this flap with carburetor cleaner. But first, remove the throttle body from the engine. Give it a nice clean and make sure that you remove everything from it. Then you can try and see if it works. If it does, then you solved the problem with the P0123 code. If the flap doesn’t work and there is too much buildup, you will need a new throttle body for your car.

5. Bad Accelerator Pedal Position Sensor

The next probable cause for this problem with the P0123 code is a problem with the throttle pedal sensor. Also known as accelerator pedal position sensor. This sensor works together with the TPS. The APPS sensor monitors the movement of the gas pedal and then works along with the TPS sensor in the drive-by-wire system.

This is rarely a problem since this APPS sensor is double protected, which means that there are two of these sensors on your gas pedal. So, if one of them fails, the other will resume working. But still, it is an option to check when it comes to the P0123 Chrysler code.

P0123 Symptoms

We have covered the P0123 causes, now it is time to cover the P0123 code symptoms. There are also a few symptoms that will be present whenever you have this issue.

So, it is worth going through them briefly before we jump into diagnosing the P0123 code on your car.

1. Check Engine Light

The first and most common symptom of this problem with the P0123 Dodge code is the problem with the check engine light.


And since you are here, you are probably aware of this situation. That’s for sure. What is also worth noting is that there could be some other codes concerning the throttle body that can indicate problems with this component. So, it is worth checking out all the different codes when it comes to this issue.

2. High Engine Idle

The second common symptom of the P0123 code is the high engine idle. The idle RPM of the engine could reach 2,000 RPM in some cases.

And frankly, this is not good. The ideal idling RPMs should never exceed 800 RPM. The RPM when the engine starts should be 1,000 and then after the engine warms up, it should drop to 800. So, if you have an abnormally high idle, then you need to consider this an issue with the TPS sensor. Now let’s move to the last probable cause.

3. Rough Idle

And the last symptom that we are going to cover is the rough engine idle. The rough engine idle can mean a lot of things. But in some instances can mean that you are having issues with the throttle body.


If the throttle body is stuck or doesn’t close well and the sensor is measuring too high of a voltage all of the time, this could mean only one thing. And that is a possible problem like in our case with the P0123 code. But how you can diagnose this problem? Well, that’s what we are going to elaborate more on next.

How To Diagnose & Fix P0123 Code?

Now let’s learn how you can diagnose a problem like this with a P0123 code on your car. What you can do in order to see what could be causing this issue?

Well, the first thing that you want to check is the throttle body and its condition. If there is a carbon deposit that is built upon this throttle body, then you definitely need to give it a good cleaning and make sure that the flap is working correctly.

If the flap is working as it should and is not stuck open, you want to check the TPS sensor on your car. And how you can do this? Well, the answer is simple, you can do this with the help of a multimeter.

For this purpose, you will be needing a multimeter and you will have to back probe two of the wires of this sensor. Back probing is a method where you will put two needles on the ground and the signal wires.

Then you will connect these needles with the multimeter with the help of alligator clamps. Then you should tweak the multimeter to DC volts and then you will have to start the car.

On a cold start, the TPS should produce about 0.95 volts. The more gas you give, the voltage should rise to up to 5V. So, if the voltage is too high on idle. It means that you have a problem with this sensor and this sensor has to be replaced. Overall, that’s all when it comes to diagnostics for the P0123 code. More on how it’s done, you can check in the video above.

Cost To Fix P0123 Code

So, we learned how we can diagnose a P0123 code, now let’s see how much money could cost us to fix this issue on the vehicle?


Overall, it is not that expensive. In most shops, you will pay about $120 for the diagnostics of the problem. Then if the TPS sensor is broken you will pay somewhere between $80 and $240. Depending on the make and model of the car and the labor required.

If you have to replace the throttle body, you can expect to pay more, a lot more, somewhere between $300 and $650.


In this article, we have covered quite a bit when it comes to the P0123 code and what is causing this problem in your car.

We have covered the main causes, symptoms, and how to diagnose this issue quickly and effectively with a multimeter. And also what are going to be the costs involved in this job.

F.A.Q To P0123

Now let’s answer some frequently asked questions.

What Does Code P0123 Mean

This code means that the PCM is registering too high a voltage in circuit A on the TPS sensor. When the voltage rises without any reason, the PCM sees this as an anomaly and reports this in the form of a trouble code P0123.

What Does A Throttle Position Sensor Do

The TPS sensor is a simple sensor that works like a potentiometer. As the throttle input rises and the butterfly flap on the throttle body opens, the sensor records higher voltage. Then this piece of data is shared with the PCM so the systems that are affected by this sensor know how to react.

How To Fix Throttle Position Sensor

Fixing this TPS sensor is only possible by replacing it, there is no way around this except by performing a replacement. They are not repairable. So, replace yours with a new one.

Where Is The Throttle Pedal Position Sensor Located

There are two throttle pedal sensors. The first is the TPS sensor which is located on the throttle body and the APPS sensor also known as the accelerator pedal position sensor which is mounted on top of the gas pedal inside of the cabin.

How To Reprogram Throttle Position Sensor

First, you need to put the key in the ignition, then turn the key to on position, and then turn it off. Don’t crank the engine, then repeat again the second step. After doing this crank the engine and pull the parking brake. Then set the gear lever to drive and wait for a few minutes. And you are good to go.

Approved Tools

These tools have been tried and tested by our team, they are ideal for fixing your car at home.

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