Thousands of system components work together in harmony to make your vehicle engine provide peak performance the way it’s supposed to, and the throttle position sensor (TPS) is one of those components that are often overlooked.
The throttle body is an essential component of fuel management that monitors the air that goes to the engine.
The collected data that enables the throttle position sensor to monitor air into the engine determines precisely the amount of gas to inject into the engine at any given time.
Suppose the throttle position sensor and its related partners carry out their duty properly. In that case, your vehicle will accelerates, coast, and cruise nice and smoothly as you expect while providing peak performance.
On the other hand, when the throttle position sensor fails, you will notice symptoms of bad throttle position sensor that can result in performance limitations, poor fuel economy, erratic idling, to name just a few.
What Is a Throttle Position Sensor?
This vital sensor allows your engine to maintain a proper amount of air. This feature is dependent on the throttle valve.
When you press down on the gas pedal, your throttle body unit’s valve opens. This causes your throttle position sensor to adjust the engine intake manifold accordingly.
This little sensor is essential to a correct mixture of air and fuel. It’s integrated with your engine control module and helps keep your idling and acceleration smooth.
When this sensor is damaged or not working properly, it’s important for you to replace it to restore your vehicle to its full performance and power.
What Does A Throttle Position Sensor Do?
The throttle position sensor (“TPS”) is a component of your car’s throttle body system. It is located between the engine’s intake manifold and the air filter.
It is vital to ensure that a specific amount of fuel and air is delivered to your car’s engine as input for the engine’s combustion. Remember the Engine101 lesson: Your car’s engine requires a precise ratio of air and fuel mixture for optimal function.
Each time you press down on the gas pedal, the throttle butterfly valve rotates to let a precise amount of air enter through the engine’s intake manifold into the combustion chamber. As you press the pedal farther in, the valve opens more.
At the same time, the throttle position sensor sends out a signal to the Power Control Module to report the position of the throttle butterfly valve.
Simultaneously, a corresponding amount of fuel is instilled into the chamber, creating the ideal conditions for the combustion to take place.
To determine the exact amount of air needed for the engine at any specific time, the car’s computer, known as the Power Control Module, collects data continuously, as much as many times per second, including air mass flow, engine RPM, air temperature, the position of the throttle butterfly valve, and how fast the valve’s position sensor changes.
If the throttle position sensor and other sensors work well, your car will maintain optimal fuel economy and smooth handling. In other words, the engine will effectively receive the optimal fuel and air input to accelerate, coast, and cruise smoothly.
Symptoms of bad throttle position sensor
The most common symptoms of a bad throttle position sensor (TPS) include the Check Engine Light turning on and a rough or inconsistent idle.
You might also notice an unresponsive throttle, loss of power, higher fuel consumption, or transmission shifting problems if the issue isn’t addressed.
Here’s a closer look at the most common bad throttle position sensor symptoms to help you spot the problem early.
#1. Check Engine Light.
The Check Engine Light comes on when the TPS sends an incorrect reading to the computer. Because the TPS is monitoring the throttle plate, any malfunction will be registered.
The throttle plate is responsible for controlling how much air gets into the engine, so it needs to be operating correctly for the engine to continue performing.
If there’s a loose connector to the TPS or the sensor fails to measure the throttle function, the light will come on the dashboard and a code will be set in the system. You can read these codes with your compatible scanner.
#2. Rough Idle.
If there’s a malfunction with the measurement or reporting of the TPS, you may notice a rough idle. Without the right information or when the engine doesn’t get the air it needs, the motor can stall.
You may notice a rougher idle just after starting the engine. It can also occur after you push down on the accelerator pedal.
Depending on what’s going on, you may notice that the idle is normal at times. For example, you may not notice any idle issues while the car is sitting in Park.
Make sure you check around the throttle because contaminants and dirt buildup can lead to an erratic idle speed. Cleaning off the throttle would be an easy fix to the problem.
#3. Unresponsive Throttle.
The TPS helps to determine engine power. If there’s a malfunction, you may have trouble getting the car to go faster when you push down on the pedal.
Acceleration can be uneven or it will stop after a certain speed. This problem can be dangerous, especially if you are attempting to merge with heavy traffic and you need the car to start moving.
On the other hand, the opposite of an unresponsive throttle can also occur. The car can start accelerating without your input.
#4. Lack Of Power.
If the throttle angle or valve position isn’t properly reported, too much air can get into the air-fuel mixture. This imbalance leads to a lack of power, especially during acceleration, as mentioned above.
This lean-running condition makes it difficult to get the power out of your car it should be giving you. If you are in a hurry or want to get the car up to highway speeds, this can be even more frustrating.
#5. Increased Fuel Consumption.
With the false readings coming from the TPS, the engine is going to consume too much fuel. While the average fuel economy is determined and confirmed by the U.S. Department of Energy, your car is going to fall short of its average rating.
What may start out as a minor decrease in fuel economy can quickly change to dramatic consumption. Yet, even with a few mpg less, you are going to be spending more on fuel. If you need to get fuel 20 miles sooner than you should have, that’s going to add up.
#6. Gear Shifting Issues.
TPS failure doesn’t always happen smoothly. If erratic signals are being sent to the computer, you may notice strange issues with the car.
At times, it could feel like you are releasing and applying the gas pedal rapidly, causing the car to shift unnaturally. This can create a bucking feeling.
In severe cases, the car can also go into limp mode. This vital safety feature keeps the engine and transmission protected, but it also makes it impossible to shift out of a certain gear.
You should only drive a car in limp mode a short distance, either to get home or to a local repair shop.
What Causes a Throttle Position Sensor to Fail?
Throttle position sensors typically have a long service life, but several factors can contribute to premature failure.
General wear and tear is the most common cause, especially in vehicles with high mileage. Many TPS units begin to show signs of deterioration after 100,000 miles of service.
Electrical issues represent another significant factor in TPS failures. Corrosion on electrical contacts, frayed wires, or poor connections can all disrupt the sensor’s ability to transmit accurate signals to the ECU.
The TPS’s location on the throttle body also exposes it to harsh environmental conditions—heat from the engine, dirt and debris from the air intake, and occasional moisture can all accelerate sensor degradation.
While less common, manufacturing defects can also lead to premature TPS failure. Some vehicle models have experienced higher rates of throttle position sensor issues due to design flaws or component quality problems.
How do you diagnose a throttle body?
Diagnosing a faulty TPS involves retrieving any diagnostic trouble codes, performing a visual inspection, testing sensor voltages, and doing a road test.
Step 1: Retrieve Engine Codes.
The first step is to retrieve any stored error codes from the ECM that caused the check engine light. This can point you towards the TPS as the culprit. Connect a code scanner and look for any P0120, or P012x codes described earlier.
Step 2: Visual Inspection.
Before testing the electrical function, visually inspect the TPS sensor and electrical connectors for:
- Damage to the sensor housing
- Loose, corroded, or damaged wiring and connectors
- Carbon buildup on sensor contacts
- Melted or frayed wires
Look for anything that could cause an open or short circuit in the TPS sensor circuit.
Step 3: Voltage Testing.
Use a digital multimeter to check the throttle position sensor’s voltage signals. This tests the sensor circuit for anomalies:
Test 1: Key On Engine Off.
- Check voltage at closed throttle – should be near 0.5 volts
Test 2: During Acceleration.
- With the engine running, quickly press and release pedal
- Voltage should smoothly sweep from low to high
Test 3: Snap Throttle Test.
- Quickly press pedal to wide open and release
- Voltage should go from low to high immediately
Compare voltage readings to specs in a repair manual. Erratic voltages point to a bad TPS sensor.
Step 4: Road Test.
Finally, do a road test for symptoms like hesitation, surging, or lack of power. Have someone monitor voltage signals during the test, looking for:
- Voltage that fails to reach extremes at WOT
- Slow/sluggish voltage response
- Erratic voltage fluctuations
This confirms if symptoms relate to faulty or out-of-spec TPS voltage signals.
Following these diagnosis steps will help isolate a bad TPS sensor from other possibilities before replacing it.
How to Replace a Faulty Throttle Position Sensor?
Tools and Materials Needed for Repair
Before beginning the repair or replacement of a throttle position sensor, it is important to gather the necessary tools and materials to ensure a smooth and efficient process. Here is a list of the essentials:
- New Throttle Position Sensor (if replacement is required): Ensure the replacement sensor is compatible with your vehicle’s make and model.
- Socket Set or Wrenches: These will be used to remove any bolts securing the sensor in place.
- Screwdrivers: Both flathead and Phillips screwdrivers may be necessary depending on the sensor’s mounting setup.
- Multimeter: Essential for diagnosing the sensor by checking its voltage readings and ensuring proper functionality.
- Cleaning Supplies:
- Throttle Body Cleaner: To remove any dirt or debris around the sensor and throttle body.
- Shop Towels or Rags: For cleaning and wiping down components.
- Protective Gear:
- Gloves: To protect your hands during the procedure.
- Safety Glasses: To shield your eyes from debris or cleaning chemicals.
- Service Manual (optional): A repair manual for your specific vehicle may provide detailed instructions and diagrams.
- Flashlight (optional): Helpful for illuminating hard-to-reach areas while working.
Having these tools and materials ready beforehand will help streamline the repair process and minimize interruptions.
Replacing a throttle position sensor is usually a straightforward process, though specific steps vary by vehicle make and model. Here is the general TPS replacement procedure:
Step 1: Disconnect the Battery.
Disconnect the negative terminal of the battery before starting any work. This avoids electrical shorts and sensor damage.
Step 2: Locate the Throttle Position Sensor.
The TPS is located on or near the throttle body assembly. Consult a vehicle repair manual to find its specific position.
Step 3: Disconnect Electrical Connector.
Locate the wiring harness connector for the TPS sensor and disconnect it. Use care not to damage it.
Step 4: Remove Mounting Bolts.
Remove the two mounting bolts securing the sensor to the throttle body. Save them for the new sensor.
Step 5: Detach Old Sensor.
With bolts removed, detach the old TPS sensor from the throttle body. Note its orientation for installing the new one.
Step 6: Install New Sensor.
Place the new TPS sensor in the same orientation as the old one and install the mounting bolts to secure it.
Step 7: Reconnect Electrical Plug.
Plug in the wiring harness connector to the new sensor, ensuring it clicks into place securely.
Step 8: Reconnect Battery and Test.
Reconnect the battery terminal. Start the engine and test acceleration for smooth operation. Clear any codes and road tests to confirm normal operation.
With these steps, you can successfully and affordably replace a faulty throttle position sensor on most vehicles in under an hour, restoring engine performance and drivability.
How to Test a Throttle Position Sensor?
You can test a throttle position sensor with a digital multimeter (DMM), a scan tool, or an oscilloscope.
Using a DMM is the method most DIYers are comfortable with. The following steps will give you an idea of what the troubleshooting process typically involves.
Note: The following are general guidelines for educational and entertainment purposes only. Consult your vehicle’s factory information for specific repair instructions and recommended safety procedures.
Step 1: Check for Diagnostic Trouble Codes (DTCs).
Is there a diagnostic trouble code (DTC) for the TP sensor stored? Then there’s probably a problem with the TP sensor or its circuit.
In most cases, cars built after 1996 with onboard diagnostics (OBD) II will set a code for a bad TP sensor. Many older cars with OBD I will also set a DTC when there’s a problem with the TP sensor. You can check for diagnostic trouble codes using a scan tool or code reader.
But keep in mind: TP sensor codes don’t necessarily mean the sensor is bad. You’ll need to do some troubleshooting to rule out problems elsewhere in the circuit.
Step 2: Perform a Visual Inspection.
If you find TP sensor-related codes stored, you can move on to performing a visual inspection. You’ll want to look for issues, such as damaged wires and poor connections.
Repair any problems found, then clear the DTCs, and see whether the problem returns.
Step 3: Test the TP Sensor Circuit with a DMM.
Next, if you didn’t find anything obvious during the visual inspection, you’ll want to test the TP sensor with a DMM. In most cases, the TP sensor will have three wires going to it: reference voltage (from the PCM), return signal (from the sensor), and ground.
Here’s how to test the reference and ground portions of the circuit:
- Put on your safety glasses.
- Consult a repair manual to determine which terminals are which on the throttle position sensor connector.
- Test for power (reference voltage) going to the sensor:
-Remove the electrical connector from the TP sensor.
-Turn the vehicle’s ignition switch ON.
-Set your digital multimeter (DMM) to the DC volts setting.
-Connect one meter lead to the battery’s negative terminal. Connect the other meter lead to the reference voltage terminal on the harness side of the TP sensor connector.
-If you see around 5 volts, the reference voltage portion of the circuit is intact. - Test the ground side of the circuit:
-Make sure the vehicle’s ignition switch is turned OFF.
-Set your digital multimeter (DMM) to the ohms setting.
-Connect one meter lead to the battery’s negative terminal. Connect the other meter lead to the ground terminal on the harness side of the motor connector.
-A reading of anything other than out of limits (OL) indicates the ground side of the circuit is intact.
If you find both sides of the circuit to be okay during testing, you can move on to checking the TP sensor itself. On the other hand, if your test results indicate a circuit problem, you’ll need to trace the factory wiring diagram and repair the issue as needed.
Step 4: Test the TP Sensor with a DMM.
Note: This test will not work on a vehicle with electronic throttle control. It only applies to vehicles with a traditional, mechanical throttle body.
- Turn the vehicle’s ignition switch ON (but leave the engine off).
- Leave the electrical connector connected to the TP sensor. Use back probe test leads to connect the DMM between the TP sensor signal wire and ground wire.
- With the ignition on and throttle closed, you should get a reading of around 0.5 volts.
- Operate the throttle cam by hand and slowly open the throttle.
-If the sensor is working properly, the voltage signal will increase as the throttle opens. -The increase in voltage should be smooth without any dropout spots.
-Once the throttle is completely open, the reading should be around 4.5 volts. - Slowly return the throttle to the closed position while looking for a corresponding decrease in voltage front the TP sensor.
-A good sensor will produce a smooth, decrease in voltage without any dropout spots.
If the TP sensor does not respond correctly to the test mentioned above—and you’ve already ensured the circuit is intact during step #3—the sensor is likely faulty and needs to be replaced.
Before condemning the sensor, however, it’s wise to inspect the throttle body for binding and excessive carbon buildup. Issues, such as these can prevent the TP sensor from reading properly.
FAQs.
Q: How do you test a throttle position sensor?
There are three electrical connectors on the sensor, the ground wire, the variable output, and the +12 volt input. Disconnect the TPS and insert the alligator test lead on the right Jack on the meter.
Turn the range switch to 20k ohm scale or 20,000 ohms. Connect the test leads to variable output, TPS ground wire, and the other lead to the +12 bolts.
Now you want to slowly move the butterfly flap in the throttle body from its close range to the full open range while watching the readings on the meter.
The reading should move steadily as you move the flap to the open range and decrease steadily as you return it. Any sudden decrease or increase on the readout signifies a lousy TPS and should be replaced.
Q: How do you reset a throttle position sensor?
The easiest and straightforward way of resetting the throttle position sensor is by unplugging the engine control fuse for 5 minutes or removing the negative battery terminal.
Q: Can a throttle position sensor cause transmission problems?
The throttle position sensor monitors the throttle position that is manually controlled by the acceleration pedal. The acceleration pedal is used to determine engine load, and if it fails, it can lead to hard shifting automatic transmission.
Q: How do you know if your throttle body needs cleaning?
The throttle body is a vital system component of your vehicle fuel management. Most issues associated with the throttle body usually need cleaning. And these issues are caused as a result of carbon buildups that require cleaning.
If you notice slowed acceleration or stuttering engine, shaky feeling while driving or uneven acceleration, accompanied by an engine warning light, you need to inspect and clean the throttle body.
Q: Should I clean or replace the throttle body?
Generally, throttle bodies need to be cleaned and not replaced entirely. However, you may need to replace specific related system components.
Whenever you notice erratic idling, engine hesitation, or any related sign of a lousy throttle body, always inspect the MAF sensor to ensure it’s working correctly, as it could be the root cause of erratic idling and engine hesitation.
Final word
Whether you followed these replacement procedures or you called for professional assistance, watching out for the listed symptoms of a bad throttle position sensor will save you from expensive replacement cost, poor fuel economy, weak acceleration, and erratic idling.
Always Inspect your throttle position sensor whenever you notice two or more of these signs at a time.