How does throttle position sensor Work? | Bad TPS Sensor Symptoms & Causes

The throttle body is a major component of the vehicle that regulates and measures the fluid flowing within the engine. The power in any vehicle can be controlled by the changes in the fuel-air ratio of the engine. These changes are managed through the various conditions of the throttle. The throttle is known as a regulator in steam engines, a thrust lever in aircraft, and an accelerator pedal in cars. The throttle body has a throttle position sensor (TPS or TP sensor) that tells the PCM about the position of the throttle. This article mainly explains the bad throttle position sensor symptoms, causes, and replacement cost.

What is a Throttle Position Sensor?

The throttle position sensor measures the openness of the throttle valve and controls the airflow through the intake manifold of the engine. This sensor is also known as the TP or TPS sensor.

Throttle Position Sensor diagram

The TPS sensor is generally installed in the throttle body to detect the throttle position magnificently. The throttle valve is installed inside the throttle body.

Sufficient fuel and air are the two major things that help the engine to keep running smoothly.

Usually, the air from the car intake is delivered to the MAF (mass airflow) sensor. This air is then routed from the intake to the throttle body of the car. The throttle body, which resembles a circular valve, is installed between the intake manifold and the air filter.

The main function of the throttle position sensor (TPS) is to measure the throttle position and the opening and closing timing of the throttle valve. This measured data is then transmitted to the PCM of your vehicle. The PCM utilizes this data to determine how much fuel should be injected into the combustion chamber and the spark timing.

There are several causes of TPS failure. Eventually, all of the failures affect the fuel economy and the performance of the engine, which can be dangerous for the driver and the other vehicles around him.

As the throttle position sensor (TPS) goes bad, it generates one or more symptoms such as poor engine performance, poor fuel economy, acceleration problems, engine stalling, rough engine idling, or check engine light illumination.

Throttle Position Sensor Working

The throttle body acts as a butterfly valve which is installed in every IC engine vehicle. The throttle valve is usually installed in between the air filter and the intake manifold. It controls the air flow to the engine.

Throttle Position Sensor Working, TPS sensor

When the driver presses the gas pedal, the engine requires some more air for the combustion within the engine cylinder.

When more air enters the cylinder, the fuel injector injects more fuel into the cylinder to ignite to get the required engine power.

Basically, the amount of air that enters the cylinder is determined by the position of the throttle. The Throttle Position sensor in the fuel management system determines the throttle position.  

As the driver accelerates the car, the TPS sensor forwards the throttle position data to the powertrain control module (PCM). The PCM uses this data to allow the throttle to intake a precise amount of air according to the engine requirements.

Higher pressure on the gas pedal will result in a wider opening of the throttle, and more air will be fed to the engine for the combustion process. Similarly, with the high amount of air, more fuel will be transferred to the cylinder in order to form a balanced air-fuel mixture for combustion. 

Symptoms of a Bad Throttle Position Sensor

As the throttle position sensor or TP sensor goes bad, it produces one of the below-given symptoms:

  1. Check Engine Light Illumination
  2. Poor Acceleration
  3. Unstable Engine Idle
  4. Misfires
  5. Acceleration Changes
  6. Poor Fuel Economy

1) Check Engine Light Illumination

The efficient working of the TPS sensor is very important for the efficient working of the internal combustion engine. However, when it goes bad, it produces different symptoms. The illuminated check engine light is one of the major symptoms of the bad throttle position sensor.

Flashing Check Engine Light

When the PCM detects something bad in the TPS, it instantly triggers the check engine light to warn the driver about the problem. The driver can then detect the exact issue by reading the trouble codes with the help of a sensor. P0121, P0122, P0123, P0124, P2135, and P2138 are some of the trouble codes directly related to bad TPS.

Read More: Causes of Check Engine Light Flashing

2) Poor Acceleration

The improper position reading of the throttle can be due to the bad TPS. The incorrect readings from the TPS will result in an inappropriate amount of air being released from the engine, creating weak acceleration. In this condition, the car will run at less than 30 miles per hour. This will result in increased fuel consumption and poor fuel economy.

acceleration problems

3) Unstable Engine Idle

As the throttle position sensor goes bad, it generates different issues, such as rough idling and engine stalling are the major symptoms of bad TPS. In such a situation, you should drive your vehicle to the nearest service center to test it and to avoid any unpleasant events in the future.

Rough Idling, engine idle due to bad throttle body position sensor

With the engine off idling, the PCM will not be able to detect the actual position of the throttle, whether it’s perfectly closed or perfectly open. This erroneous information can therefore cause the engine to stall.

4) Misfires

The throttle position sensor uses to monitor the amount of air flow through the intake manifold of the engine. When it goes bad, your engine may start misfiring. The misfire is very dangerous for your vehicle. It may badly damage your engine. Therefore, when you notice an engine misfire, you must address it as soon as possible.

engine Misfiring

5) Acceleration Changes

One of the unusual symptoms of a bad TPS involves increased car speed without pressing the accelerator pedal. The car will reach higher acceleration during normal driving conditions. This can therefore be very dangerous and life-threatening. This symptom of acceleration increase is the only one that happens only due to a bad throttle position sensor.

Symptoms of Bad Throttle Position Sensor

6) Poor Fuel Economy

Poor fuel economy is one of the clear symptoms of a bad TPS sensor. The air and fuel are transferred to the engine based on the readings of the TPS.

Poor fuel economy

The proper combustion of the air-fuel mixture generates power that is used to move the vehicle. Incorrect reading of the throttle position sensor can result in too much fuel being fed into the engine. The burning of a large amount of fuel will result in poor fuel economy.

Similarly, some other sensors also depend on the TP or TPS sensor readings, and a bad TP sensor will result in improper readings and very little or very much air intake.

Read More: Bad PCM Symptoms and Causes

How to Replace a Throttle Position Sensor?

  1. Remove the Battery: Before starting your work, disconnect the negative terminal of the battery. This will protect you from shocks and other parts damage.
  2. Disconnect Old Sensor: Search for the TPS. It will be present in the throttle body. Carefully unplug the wiring harness present between the computer and the sensor.
  3. Remove Mounting Screws: Remove the screws that hold the sensor.
  4. Remove the old Sensor: Grab the sensor and remove it.
  5. Install the new Sensor: Attach the screw to the new sensor to keep it in place.
  6. Re-plug the Wiring harness: Now, carefully reconnect the wiring harness. Clips and connectors should be properly aligned for proper functioning.
  7. Reconnect the Battery: Finally, reconnect the battery’s negative terminal. Hurrah! It’s done.

Safety Tips While Diagnosing the TPS Sensor

  • Before beginning work, be sure the battery has been removed. Finding out that you are working with live wires the hard way is not enjoyable.
  • Wear gloves and safety glasses to protect your hands and eyes when working in this area.
  • Anytime you plan to operate inside the engine, park your automobile on flat ground. 
  • Try to choose a quiet parking lot or location away from traffic and moving cars if you don’t have a secure parking area or garage to work in.

Replacement Cost of Throttle Position Sensor

A proper supply of air and fuel is compulsory for the efficient working of the engine. The TPS helps the PCM to ensure the proper supply of air to the combustion chamber.

The combustion process will not work properly if there is an improper amount of air or fuel. This entails insufficient electricity production as well as a number of other problems.

After the detection of the bad TPS, replace the sensor immediately. The replacement cost of the throttle position sensor highly depends on the vehicle model, labor cost, and the brand of the parts.

The average replacement cost of the throttle position sensor is from $100 to $210. In this cost, the labor cost is from $30 to $90, while the cost of the part is from $25 to $105.  

FAQ Section

What is the function of the throttle position sensor?

The main function of the throttle position sensor is to measure how open the throttle valve is and sends this information to the PCM. The PCM uses this information to regulate the amount of air that can flow into the engine’s intake manifold.

Are the gas pedal and the throttle position sensor the same?

No, they are not the same. The car with the electronic throttle control will have the APS or accelerator pedal sensor.

How long does a Throttle Position Sensor last?

The TPS is designed to function for the whole life, but sometimes it may go bad due to some issues. The batteries in the TPS last about five years. These batteries are built into the sensor and are non-replaceable. So, it is always recommended to replace the throttle position sensor every five years.

Can I drive with a bad Throttle Position Sensor?

Usually, you can drive with a bad throttle position sensor. However, it may result in a sharp increase in acceleration, rough idling, and low power while accelerating. These problems can create some dangerous situations for you while driving. So, always take your car to the service center to get it fixed.

Can a throttle position sensor cause transmission problems?

The throttle position sensor monitors the position of the throttle that is controlled by the gas pedal. This sensor is used to gauge engine load, and automatic transmission shifting issues may result if it malfunctions.

What are the signs of a bad TPS sensor?

  • Check engine light illumination
  • Jerky acceleration
  • Unexpected idle spikes
  • Unexpected engine stoppage that occurs suddenly
  • Hesitation while accelerating
  • Sudden increases in speed when you’re on the highway
  • Having trouble shifting gears
  • Poor fuel economy
  • Poor engine performance
  • Misfire

What causes throttle body to gad?

Internal contamination is one of the major causes of a throttle body to go bad. This contamination results in the improper and difficult movement of the valve and hence the air flow issues.

Is a throttle position sensor trigger a code?

If the voltage value is absent, irregular, sluggish, or consistent, a defective TPS might trigger a trouble code in the computer, which can cause your check engine light to come on.P0121, P0122, P0123, P0124, P2135, and P2138 are some of the trouble codes directly related to bad TPS.

Can a bad throttle body damage engine?

Yes, your engine might be damaged if you drive for a long time with a damaged throttle body.

What type of signal does a TPS sensor produce?

The throttle body’s butterfly valve angle position is translated into a voltage signal by the TPS sensor unit, which is positioned there, and sent to the PCM unit.

Will a throttle position sensor cause a misfire?

Engine misfires, stalling, and rough idling are the symptoms of a bad TPS. As you observe misfiring issues, you need to fix them quickly.

Read More
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  3. Bad IAT Sensor Symptoms and Causes
  4. Bad Knock Sensor Symptoms and Causes
  5. Bad Camshaft Sensor Symptoms and Causes

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