The throttle position sensor or TPS is part of your vehicle’s fuel system. Its job is to make sure that the correct blend of air and fuel is utilized in your engine. The TPS works with various other sensors to ensure your vehicle’s power and performance as well as fuel economy. If your TPS goes bad, you’ll definitely want to fix or replace it as soon as possible to keep your vehicle running as it should.
ProSource Diesel takes a look at exactly what a TPS is, what it does, and what to do about it if it goes bad.
The throttle position sensor monitors the air and fuel intake of the engine. It determines the throttle position and then transmits that to the engine control module, or ECM. The TPS is part of the fuel management system and the data that it generates is used along with other engine data like airflow temperature and engine speed.
In older vehicles, the TPS was physically attached to the actual throttle and it monitored the position based on that direct contact. However, in modern vehicles with advanced technology, the TPS works without direct throttle contact.
As mentioned above, older versions of the TPS are located directly on the throttle body so that it can monitor the actual throttle position. Modern sensors are not usually in contact with the throttle and the sensor circuit board is usually mounted inside the ETC gearbox cover.
These electric versions of the TPS are also called drive-by-wire systems or electronic throttle control systems. Some sensors are removable, but others are integrated into the electronic control throttle body.
The TPS is not likely to go bad without any warning signs. One of the first signs you might see is a warning light on your instrument panel. This light probably won’t tell you that it’s the TPS, so let’s take a look at some physical signs:
Since the TPS helps control the proper air-fuel mixture, you can expect various symptoms that reduce your vehicle’s power and performance.
If you’re experiencing any of the above symptoms, one of the first things you can do is test the TPS with a multimeter. You’ll need to ground the connector terminals and then put the multimeter probe on black for negative and red for positive.
Make sure the throttle is closed, which can be done by turning the key in the ignition without starting the engine. Read the voltage from the multimeter. The voltage reading should be between .2 and 1.5 volts. When the throttle plate is opened, it should go up to 5 volts. If it doesn’t, then it needs to be replaced.
You might be tempted to unplug the TPS if it’s broken and you want to put off fixing it. However, the long-term consequences of unplugging your TPS is not good. If you unplug it, you will experience many of the same issues as a faulty sensor.
You won’t be getting the proper air-fuel mixture and that will result in your fuel economy being reduced as well as the performance of your vehicle.
Replacing the TPS is not terribly difficult if you have some DIY vehicle knowledge. The first step is to disconnect the battery. Make sure to wear safety glasses and gloves and park your car on a level surface. Follow these steps to replace the TPS:
If you’re having trouble locating the sensor, check your maintenance manual. Different vehicles may have different locations. You might also find different methods to adjust the sensor after installing it.
After installing a new sensor, you may have to calibrate it. Having an uncalibrated sensor is basically the same as having a faulty one. The timing of calibrating a sensor is important, so you might need to keep a timer handy when you follow these steps.
Step 1 – Make sure the gas pedal is fully released, then turn the ignition on and wait for 3 seconds.
Step 2 – Stomp on the gas pedal hard and then fully release it as quickly as possible 5 times in 5 seconds.
Step 3 – After completing the previous step, wait 7 seconds and then step on the gas pedal so it goes all the way down. Leave it for 20 seconds until the check engine light (CEL) stops blinking and stays on.
Step 4 – Fully release the gas pedal within 3 seconds after the CEL comes on.
Step 5 – Start the engine and let it idle for at least 20 seconds.
Step 6 – Rev the engine two or three times to make sure the idle speed is within spec.
The simplest way to reset your TPS is to remove the negative cable from your battery for about five minutes. Or, you can remove the fuse for your ECM. However, if you’re uncomfortable working with the electrical parts of your vehicle, you shouldn’t attempt this. Removing the wrong fuse or cable can be dangerous.
Another way to reset it is with an OBD scanner, such as this one from Autel. With this scanner hooked up, you’ll need to access the app. The path for this should be service >> throttle >> vehicle make >> manual selection >> model year >> vehicle model >> hot function >> learn electronic throttle control >> Ok
The app will then instruct you on what to do to reset the throttle position.
The procedure might be different for different scanners. With your scanner plugged in, if you can find something like TP Position Check, you can then reset the TP Learning Value. Then your vehicle needs to relearn the position, and this procedure varies by vehicle, you’ll need to check your service manual.
If you get your TPS replaced by a pro, you can expect to pay between $150 and $250, but the majority of that cost is labor. Prices for the actual part can vary widely by vehicle. You might find one as cheap as $40 or as expensive as $200.
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