Cars contain a lot of obscure, very specific components that can completely screw up your driving experience if they fail. One such component in the throttle position sensor (TPS), which is a sensor that, as the name implies, measures how far the throttle has been opened when you push on the gas pedal.
Having an uncalibrated TPS is more or less the same as having a malfunctioning TPS. The sensor will be unable to accurately determine the position of the throttle and as a result, your air/fuel ratio will be completely off. This can lead to numerous symptoms, which we’ll go over in this article.
In addition, we’ll be explaining more about what exactly a TPS does and how you can calibrate a new TPS on your own.
What Is a TPS, and How Does It Work?
We’ve mentioned this briefly already, but let’s quickly go over in a little more detail how exactly the TPS in your car works. As you know, the TPS is used to measure how open the throttle is, which is useful for determining the correct air/fuel ratio.
The TPS is almost always located on the throttle body and generally works in one of two ways. If you have an older car with an older style of TPS, the sensor contains contact points that physically monitor the position of the throttle, but newer sensors measure throttle position by detecting differences in magnetic fields when the throttle position changes.
When the TPS detects changes in the throttle position, it sends a signal to the engine control module (ECM), which is essentially the main brain of the engine that controls things like the air/fuel mixture, ignition timing, and idle speed.
What Happens If My TPS Is Faulty or Uncalibrated?
If your TPS is faulty or uncalibrated, the sensor will be unable to accurately determine the position of the sensor. This will lead to a variety of symptoms, all of which are caused by the fact that the ECM is delivering the wrong air/fuel ratio to the cylinders thanks to the bad sensor.
If you notice the signs of a faulty TPS, it’s important that you have it recalibrated or replaced as soon as you can. Driving for too long with a bad TPS can potentially cause even more serious issues and lead to an even more expensive repair bill.
If you notice a few of these symptoms occurring when you drive, it might be a good idea to inspect your TPS:
Check Engine Light Is On
Part of the ECM’s job is to monitor the information sent to it from various sensors and compare it to the information it’s receiving from other sensors to try and figure out if something isn’t working right. If the ECM thinks that the information it’s getting from the TPS doesn’t match the information it’s getting from the other sensors, this will light up the check engine light.
A check engine light on its own obviously doesn’t mean that the TPS is faulty, as the check engine light will turn on for any number of engine-related issues. However, if you notice the check engine light in conjunction with the symptoms listed below, there’s a good chance that a bad TPS is the cause.
Read: Bad TPS Sensor Symptoms
Engine Doesn’t Make Power
If the TPS is causing your ECM to think that the throttle is closed when it isn’t, it’ll reduce the amount of fuel in the air/fuel mixture and cause the engine to run lean. Without enough fuel in the mixture, the engine will fail to make as much power as it normally does.
When this happens, you’ll likely notice it the most when you try to accelerate. Your car may accelerate normally at first, but as you shift into higher gears or get higher up in the rev range, you’ll notice that after a certain point your car will simply refuse to accelerate any further.
The same can also happen in the opposite case if the TPS tells the ECM to add too much fuel instead of too little. In this case, your car will also get worse gas mileage than it normally does, and you might notice a persistent smell of gas while driving your car when previously there was none.
Car Jerks and Accelerates Unintentionally
Occasionally, the TPS can fail in such a way that it sends a sporadic signal back to the ECM. When this happens, the ECM will think that the throttle is constantly opening and closing, and it will make adjustments to the air/fuel mixture accordingly.
During driving, this will cause your car to jerk suddenly, and you may even experience brief periods of acceleration even when you’re not trying to accelerate.
When you don’t have your foot on the gas pedal and the engine is idling, the TPS is one of the things that allows your engine to maintain a proper idle speed. If the TPS is faulty or uncalibrated, however, then it’ll mess with the amount of fuel getting to the engine and cause it to idle rough.
Ideally, an engine at idle should maintain a pretty consistent number of RPM, but an engine with a bad TPS will keep slowing down and speeding up when at idle.
How to Calibrate a TPS
Calibrating a TPS can be relatively easy if you know what you’re doing. The problem is that the exact method used to calibrate a TPS can vary based on several things, including the specific TPS and ECM you have.
Some sensors can be calibrated manually with just a multimeter, while others may be calibrated with tuning software. If you want instructions on how to calibrate the TPS for your vehicle, your best bet would probably be to search how to calibrate a TPS in that specific vehicle or to take your car to a repair shop and have it done there.
How to Replace a TPS
On the other hand, if your TPS has gone completely kaput and you just want to replace it with a new one, this process is more or less the same no matter what kind of car you have. It’s also a pretty easy repair to make, and you don’t need too many different tools to do it either.
Here’s what you’ll need to replace the TPS in your vehicle:
- A multimeter
- A screwdriver set
- Work gloves and safety glasses (just to be safe)
- Replacement TPS (make sure you buy one that’s actually compatible with your vehicle)
Once you’ve gathered your tools, follow these steps to replace your TPS:
- Disconnect the car battery before doing anything else. You’ll be handling your car’s electronics, and the last thing you want to do is give yourself an electrical shock.
- Find the TPS, which should be located on the throttle body. Disconnect the wiring harness connected to the TPS.
- Remove the screws holding the TPS in place on the throttle body. You may need a screwdriver with a Torx bit to do this but in some cases, you may find that the TPS is held in place by security screws with no slots. In this case, you can use a hacksaw to make your own slot and unscrew the TPS with a flathead screwdriver.
- Once you’ve fully unscrewed the TPS, remove it from the throttle body by pulling it off. You can throw the old TPS out at this point.
- Take the replacement TPS and screw it back onto the throttle body. Make sure you install the new TPS in the same position as the old one.
- Plug the wiring harness into the new TPS, making sure to properly align all of the various connectors.
- Reconnect the battery, and test your repairs by taking your car out for a spin. If it runs normally, then congratulations! You’ve managed to successfully replace your TPS.