Information on the Throttle Position Sensor in a 2004 Nissan Sentra

by Edmund Gary

The 2004 Nissan Sentra, like most cars built after 1996, uses a throttle position sensor to help improve the car's emissions system. The sensor feeds the information into the car's computer and adjustments are made to the engine so the car can operate smoothly. The throttle position sensor or TPS is vital part of the modern car.

Definition of a Throttle Position Sensor

The throttle position sensor measures the position of the throttle in an internal combustion engine. The sensor is located on the butterfly spindle so it can directly measure the position of the throttle valve. The sensor provides a resistance signal to the engine control unit (ECU). The Nissan Sentra TPS is located on the throttle body and is secured in place by two screws. A three prong plug is connected to the sensor.

Potentiometer

The TPS is a potentiometer. A potentiometer is a three terminal resistor with a sliding contact. This forms an adjustable voltage divider. Variable resistance is dependent upon the position of the throttle valve. The sensor's internal variable resistor rotates whenever the accelerator is pushed. Voltage from the TPS adjusts the engine functions. In extreme situations, extra fuel is is injected when the throttle is opened rapidly. This helps to avoid stalling, like an accelerator pump of a carburetor engine.

TPS Voltage Adjustments

The Sentra throttle position sensor produces 0.45 and 0.55 volts. If the voltage is not in that range, the TPS can be adjusted. The TPS on other cars can not be adjusted. The wiring harness can be disconnected from the TPS. Positive and negative leads should be inserted into the TPS. The leads should not touch. The ignition key should be switched to the ON position, with the engine off. The TPS will have to be loosen from the throttle body and rotated until the proper voltage is reached. The final check is conducted by opening the throttle all the way. The reading should be 4 volts.

Symtoms of a Bad Throttle Position Sensor

A bad throttle position sensor can bring some unpleasant symptoms to the car. Hard starting or no starting and stalling are the result of a bad TPS. Other symptoms are rough idle, variable idle speed, backfiring and a significant drop in fuel economy. Driving the car will become a challenge because it will not supply the assurance that is needed at critical moments. The car's warning system will alert the driver whenever the TPS is going bad: the service rngine light will illuminate. The driver may experience difficulty changing gears and suffering fuel economy.

TPS and Vehicle Electronics

The throttle position sensor of the 2004 Nissan Sentra is no different from the TPS of most newer makes and model cars. The TPS has become a vital part of the car's engine. Nissan Sentra models do not have a direct link from the accelerator to the throttle like the cars did decades ago.

About the Author

Edmund Gary began writing on a volunteer basis in 2001. He writes press releases and newsletter articles which center around the activities of his Knights of Columbus Council. His stories appear in "Knightlife," the official publication of the James C. Fletcher, Jr. Council No. 11422. Gary has a Bachelor of Fine Arts from Bowie State University.

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