Your car has dozens of sensors onboard—one of which is the throttle position sensor (TP). As you might have guessed, the TP sensor measures the position of the throttle blade.
Older vehicles have just one TP sensor, whereas newer models with electronic throttle control (ECT) have two sensors as a fail-safe measure.
Although the TP sensor is a relatively simple part, it can cause several noticeable symptoms if it fails.
What Is A Throttle Position Sensor?
The throttle position sensor monitors how far open the throttle valve (or blade) is open, which is determined by how far down the accelerator pedal has been pushed. The throttle position controls the amount of air that flows into an engine’s intake manifold; when it’s opened wide more air flows in; when it’s nearly closed, little air flows in.
The position of the throttle and how quickly it’s opening or closing is transmitted to the engine control module, and that information is among the factors the computer uses to decide how much fuel is injected into the engine and the spark timing. The TPS is usually mounted on the throttle body (the housing that contains the throttle valve).
When a TPS malfunctions it can trigger a “check engine” warning light or cause the engine to idle roughly, surge, hesitate or stall because the engine control module doesn’t know what the throttle position is and can’t correctly set the fuel mixture or ignition timing.
Key Takeaway:
- The throttle position (TP) sensor measures the position of the throttle blade.
- A bad TP sensor will show symptoms such as an illuminated check engine light, engine and transmission performance issues, and the vehicle being stuck in limp mode.
- Diagnosing a bad TP sensor involves testing the part. To do this, check for diagnostic trouble codes first. Then, use a digital multimeter to check if the sensor is functioning.
Symptoms Of A Bad Throttle Position Sensor
There are many symptoms of a failed throttle position sensor. While some of these symptoms could also be signs of other engine issues, watch out for these symptoms of bad TPS, or throttle position sensor.
The most common symptom is your check engine light. This indicator is a vague symptom, as it could also point to a variety of issues, but you can expect to see it if there’s any issue with your throttle position sensor.
Next, any unusual changes in your acceleration could be linked to this sensor. During your normal driving, consider inspecting your sensor if you experience any of these throttle position sensor symptoms.
Symptoms of a Faulty Throttle Position Sensor:
- Hesitations during acceleration.
- Poor power.
- Difficulty and/or delay in gear shifting.
- Unusual surges while accelerating.
- An unexplainable bucking and jerking in the vehicle.
- Sudden engine stalling without any apparent reason.
- Intermittently flashing of check engine light for no apparent reason.
- A drastic drop in fuel economy.
Each of these could be signs that your throttle position sensor isn’t working correctly. Too much airflow or too little could cause poor acceleration performance, but it could also be linked with other engine issues. If you notice your fuel economy has dropped dramatically, it could be a result of an improper fuel and air mixture.
Similarly, if your engine struggles to idle efficiently, it could also be a result of a damaged throttle position sensor. Stalling, surging, or hesitating while idling all can be caused by this unassuming sensor.
The best way to determine if these issues are caused by your throttle position sensor is to go to the source. By using a multimeter, you can determine if the sensor has an electrical connection issue. Check the engine control module for the trouble code that resulted in your illuminated check engine light to see if it is linked with your throttle position sensor. These two steps can also help you determine whether you need to repair, replace or reprogram your sensor.
How to Test the Throttle Position Sensor?
If you own a multimeter, testing a TPS on your vehicle is a rather straightforward process. The following is a step-by-step guide on how to test a TPS sensor.
#1. Find the throttle mechanism.
The housing that is connected to the engine compartment will remain what it is. It will be the point from where the gasoline line branches off.
There will be a device attached to the throttle body which has cables leading to the engine control unit (ECU). This is the sensor for the position of the throttle.
#2. Find the wires that go to the power source, the ground, and the signal.
After you have determined the components, the next step is to locate the power, ground, and signal lines.
Simply said, this is due to the fact that all automobiles employ the same colors. The black cables represent the ground, while the red lines represent the electricity. The wire that carries the signal will be a different color, such as yellow, green, or blue.
#3. Examining the reference voltage.
Adjust the dial on the multimeter so that it reads volts. You will need to examine the voltage that serves as a reference. This demonstrates the voltage that is passing in between TPS and also the ECU.
To verify that it is working correctly, connect the negative meter probe to positive tab on the TPS wire and then connect the positive probe to the negative tab. If everything is functioning properly, the reading on the multimeter should be at about 5 volts.
#4. Evaluate the signal voltage.
At this point, you need to examine the voltage of the signal. In order to do this, you must first connect the positive probe to the signal wire tab, and then you must connect the ground probe to the frame of the vehicle. A voltage of half a volt is considered to be acceptable.
Can I Replace My Throttle Position Sensor At Home and How Much Will It Cost?
Assuming there’s nothing else wrong with your fuel system or other sensors, you’ll likely be able to escape this situation without a major financial outlay. In most cases, having the TPS replaced will cost between $150 and $250, with the majority of that cost paying for labor.