Error Code PO122: What Does It Mean?

Error Code PO122: What Does It Mean?

You’ve used an OBD2 scanner on your car to run diagnostics on it, only for it to give you this code: “PO122.”

You’re left wondering what it means. In case your scanning device doesn’t have an error code database, it helps to know that this code refers to the voltage of your throttle position sensor and it means that it’s too low. 

What, exactly, is a throttle position sensor? This is a sensor in your car that monitors the position of the throttle and sends this data to the car’s electronic control module (ECM).

This sensor has components that can become worn over time. If your throttle position sensor is giving you low voltage readings, then you’ll need to figure out what’s going on and how to fix it. Here’s what to do.

Why Is The Throttle Position Sensor Experiencing Low Voltage?

Why Is The Throttle Position Sensor Experiencing Low Voltage?

Before you can figure out why you’re getting that error code, it helps to know what’s causing low voltage in your sensor.

There are various reasons for the sensor to be experiencing a lower than normal voltage, such as the following:

  • The throttle position sensor is loosely-mounted. 
  • There’s an electric short on the sensor circuit. 
  • The sensor itself is faulty. 
  • The switch of the throttle position is malfunctioning.
  • There are damaged wires or connections in the sensor.

What Are Symptoms Of Throttle Position Sensor Low Voltage?

What Are Symptoms Of Throttle Position Sensor Low Voltage?

Besides the “check engine” light coming on in your car to alert you to the problem with the sensor, there are other symptoms that can occur which will reveal that the throttle position sensor has a problem of low voltage.

These include the following:

  • It feels difficult to start your engine. 
  • The engine doesn’t seem to have power when accelerating. 
  • When your car is on idle, it feels high, low, or rough. 
  • The engine is stalling.

How To Fix Throttle Position Sensor Low Voltage

It’s worth noting that this type of error is quite serious. When it happens, your car’s engine control unit (ECU) will go into what’s known as failsafe, or limp, mode.

This means that you will battle to accelerate because the car’s speed will be reduced. Stalling will also be common. This is why it’s important to repair the problem as soon as possible. 

You can try to fix the problem yourself if you know your way around cars, but it’s worth bearing in mind that since a low voltage of the throttle position sensor can have various sources it might be better to contact a mechanic.

If you need to replace the throttle position sensor, and you’re sure that this is what’s causing the problem, it helps to keep an eye out for other symptoms in your car that will further confirm your diagnosis.

These include the car hesitating, not accelerating properly, having rough idle, as well as releasing more emissions than it should.

And, of course, if the “check engine” light comes on along with those other symptoms, that’s a dead giveaway. 

You can replace your throttle position sensor by following these steps:

  • First, make sure you have all the materials you’ll need. These include a pair of protective gloves, safety glasses, a screwdriver, and a voltmeter.
  • Once you’ve located the throttle position sensor (which can be found on the main body of the throttle), you will disconnect its negative battery cable.
  • Then, remove the electrical connector. You can do this by pressing down on the tab and sliding it off.
  • With a screwdriver, remove the mounting screws on the sensor so that you can remove the sensor.
  • Once that’s been taken out, you can mount the new sensor. Install the mounting screws to keep the sensor in place. You need to use a screwdriver to ensure that they are tightened properly so that the sensor will remain securely in place.
  • Make sure you reinstall the electrical connector and the cable so that everything’s connected again.
  • You might also have to adjust the sensor. You can do this with the use of a voltmeter and back probe leads to the sensor signal wire and ground. You will need to put the car’s engine on and loosen the sensor screws, then turn the sensor so that you get the reading you want. Bear in mind you will need to consult with your car’s service manual to find the sensor specifications to use.

Is It Safe To Drive With A Bad Throttle Position Sensor?

Is It Safe To Drive With A Bad Throttle Position Sensor?

While you might wish you could ignore your car’s “check engine” light when it fails to go off, that is only the case for some faults.

A malfunctioning throttle position sensor will not result in your car working in the way it should, so you should never ignore its warning signs.

In fact, it will not be safe to drive your car, and chances are you won’t even be able to because your car will lack acceleration and keep stalling.

If you ignore the malfunctioning throttle position sensor instead of attending to the problem, this could result in more damage and more expenses to repair your car down the line.

It’s also worth mentioning that the trouble codes that you’ve seen on your car scanning tool about the throttle position sensor won’t go away – they have to be fixed and cleared.

If you don’t resolve the problem that’s causing them to be generated, it could cause you further problems, such as your car failing its emissions test because a malfunctioning throttle position sensor will increase your car’s emissions, or you might be unable to sell your car. 

So basically, if you need to repair the throttle position sensor on your car, don’t delay in doing so. Drive straight to your mechanic or fix the throttle position sensor yourself if you know your way around cars.

What Are The Two Types Of Throttle Position Sensors?

What Are The Two Types Of Throttle Position Sensors?

It helps to know a bit more about throttle position sensors. There are basically two types of them, the switch and potentiometer type. Let’s see what they’re about in greater detail.

Switch Type Throttle Position Sensors

In this type of sensor, the switch remains on. This means that it can provide a constant flow of electricity while the throttle is being used.

When the throttle isn’t in use, the switch will go off and not allow the electrical flow to occur.

Potentiometer Type Throttle Position Sensors

This type of sensor works a bit differently. It sends low voltage to the ECU in the car engine when the ignition is switched on but the throttle is off.

Then, it increases the voltage when the throttle is increased. It will usually reach a maximum of five volts. 

Extra Tips for Fixing Your Throttle Position Sensor

Extra Tips for Fixing Your Throttle Position Sensor
  • You should always check the sensor’s wiring before you go ahead and replace the throttle position sensor. If the wiring is loose, it can cause the sensor’s reading to be false. This will also be an easier fix than if you go ahead and replace the sensor because you might not need to do that.
  • What about the voltage? Now, you might be wondering what voltage is normal. The powertrain control module or PCM as it’s referred to, in your car will give a voltage of five volts to the sensor. Generally, at idle the car will have .5 volts, and at full throttle close to five volts. If the PCM notices that the amount is lower or higher than it should be for a specific RPM, it will send a trouble code to the car’s computer.

Related Questions 

What is limp mode and why does it happen?


Limp mode is when your car has detected a serious fault. It’s a security feature that decreases the RPMs and power of the engine so that you can safely drive to the closest workshop without causing further damage to your car.

How much does it cost to replace a throttle position sensor?

You can expect an average cost of between $170 and $219. Labor costs are between $59 and $74, and the parts cost between $112 and $145. 


Your car’s throttle position sensor is an important component that you have to ensure is working properly.

If it isn’t, this can point to problems with your car, or it can be failing as a result of the sensor itself needing to be changed. If that’s the case, we’ve provided you with the steps you need to follow in order to successfully replace it. 


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