Throttle Position Sensor (TPS)

"I step on the accelerator all the way and it doesn't respond" This may be due to a problem with the TPS Sensor (also known as Throttle Position Sensor). This sensor is responsible for checking the position of the throttle located right at the intake of the vehicle's engine. In this article we want to help you find out all about this sensor that is activated when the vehicle's accelerator pedal is pressed to accelerate. This way you will have all the necessary knowledge to solve any failure and perform its due maintenance.

What is the TPS Sensor?


The TPS sensor is a small transmitter that controls fuel injection by sending a signal to the computer. When the throttle is opened, the air is allowed to enter the engine. This action is made possible by a throttle or foot pedal-operated steel cable.

Simply put, the TPS is a power sensor, powered by 5-volts. To operate, it uses a resistor and a moving brush. The voltage varies according to the position of the shaft and the resistor.

How does the TPS throttle position sensor work?

The Throttle Position Sensor (TPS) is responsible for studying the position of the throttle valve of the air inlet that goes to the engine, sending a signal to the ECM (Engine Control module) that uses this information to control the times of fuel injection to the combustion chambers. When the engine is idling, the Throttle Position Sensor (TPS) sends a signal equivalent to 0 degrees towards the Engine Control Module (ECM), taking control of the ECM on the engine revolutions depending on the coolant temperature of the engine, the gases that enter the engine and the electric charge requested by the car at that moment.

The signal that the TPSsensor delivers to the ECM (Motor Control Module) is a voltage signal, which varies with the position of the accelerator. When the vehicle is accelerated or idling, the TPS sensor output is low, within 0.4 to 0.8 volts. Depending on the acceleration, the signal voltage of the TPS will rise until it reaches its maximum value of total acceleration, which is between 4.5 to 5.0 volts.

What does the TPS sensor include?

For proper operation, the sensor should generally contain the following parts:

  • 5-volt reference cable
  • Ground wire
  • Return signal cabl

What is the TPS Sensor used for?

The Throttle Position Sensor is responsible for letting the ECU know what state the throttle butterfly is in. If the throttle body is not actuated, it cannot respond to the driver's commands.

Depending on the acceleration of the vehicle, the throttle position sensor can move up to 100 degrees. Obviously, if the vehicle is not running, the throttle is closed and the sensor is at zero degrees.

The TPS sensor has an influence on the following functions:

  • Doses the amount of fuel.
  • Controls the idle speed.
  • Disconnects the air conditioning when there is sudden acceleration.
  • Controls the operation of the Canister.
  • How does the TPS Sensor work?
  • The TPS sensor indicates the position and opening of the throttle valve. This information is sent to the main computer, where the information is validated to make the engine work properly.

Types of TPS Sensor

Basically, there are two types of Throttle Position Sensors with few differences between them.

  • The first one is composed of three wires or connections. One connection or cable is the one that indicates the voltage, which is generally 5-V, the other cable would be the ground pole and the last one would be the one that indicates the signal that is transmitted to the computer.
  • And the other sensor has four wires or four connections, of which three fulfill the same functions of the previous one explained. With the only difference that this one contains added a fourth cable or connection, which would be the idle contact.

Common Throttle Position Sensor Faults

When the TPS Sensor is not functioning properly, the computer does not send the correct signals to the engine to perform combustion. In these cases, some fault symptoms occur such as:

  • Unstable idle or heavily throttled engine.
  • Lack of power, which may indicate a damaged TPS sensor.
  • The engine pulls, which are common when one of the sensor pins is broken.
  • Check engine light illuminated on the engine dashboard.
  • Temperature mismatch can change abruptly.

Any of these faults may suggest a damaged, broken, or misplaced TPS sensor.

The TPS Sensor can exhibit faults that are diagnosed with the OBD2 protocol, using a scanner. In this case, the most common codes are:

P0122: It means that the output voltage of circuit A of the sensor is below correct.

P0123: This code is the opposite of the previous one. That is, the engine control module or ECM exceeds the voltage expected by the sensor.

How to test if the TPS Sensor is working?

To check if the Throttle Position Sensor is in good working order, a multimeter or oscilloscope is required. Ideally, the TPS sensor should be checked every 20,000 kilometers. In addition, the points to check are that the wires are not broken and that the harness is free of rust.

Now, measure the TPS Sensor connector according to the following steps:

  1. Measure the potentiometer current to see if it sends the signal back.
  2. With an oscilloscope on the TPS Sensor move the throttle and verify that the signal goes up or down. If it does, it means that the sensor is working properly.
  3. The sensor signals should equal 5-volts at any point.

How to clean the TPS sensor?

It must be said that the Throttle Position Sensor does not clean itself. What you need to clean is the throttle body to ensure optimal operation of the TPS Sensor. For this, you need a clean cloth and carburetor fluid. Then, remove all the excess dust and dirt around it.

In other cases, the throttle body may be very dirty. If that's your case, the best thing to do is to disassemble it and apply a special cleaning solvent. It is important to remove the TPS sensor during cleaning to avoid contaminating the wires or damaging the sensor.

Throttle Position Sensor (TPS) Location

The TPS Sensor is usually attached to the outside of the throttle body frame and it's connected to its shaft. The throttle body is located at the air intake of the engine, and will open or close in response to the throttle movement.



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