Throttle Position Sensor Troubleshooting

Troubleshooting a throttle position sensor is essential because it plays a crucial role in the functioning of a car. This article explains how you can solve problems with this sensor.
The throttle position sensor (TPS) is one of the sensors on a vehicle which monitors the position of the throttle in the engine of the vehicle. Typically, this sensor is a potentiometer, and so it puts up a variable resistance which is based upon the position of the valve. The signals from the throttle sensor are tracked by the engine control unit in the form of an input to its control system. The timing of the ignition and fuel injection are influenced and modified by the position of the throttle. Hence, this sensor is of great importance, since if there is any problem with the throttle position, it immediately passes on the signal to the requisite control unit. This can avoid further damage of the sensor and consequently the car. There can be car problems if this sensor malfunctions. These problems can be fixed with knowledge of the TPS.


All you need is a voltmeter and two pins to repair a broken TPS. If the sensor is not working properly, the computer of the engine will not send the appropriate messages.

Step 1
First, you will need to find the location of the sensor in the engine compartment. It is usually to the right or left of the carburetor plate shaft. You can identify it by a small black box with three wires coming out of the electrical connector.

Step 2
Now, you will need to unplug the TPS connector and turn the ignition switch on without starting the engine. With the help of a connector, probe the connector's terminals, the ones which can be seen coming from the end of the engine's computer. This is needed to test for supply voltage.

Step 3
Get the negative lead to touch the connector's terminal ground. This is usually a black wire. Then, connect the meter's positive or red lead to the connector's terminal reference voltage wire which will be a blue or gray wire. The reading should be a steady 5 volts at the terminal. The supply wire can be said to be open or short if the reading does not go to the 5 volt mark. This is one of the significant symptoms of a bad sensor.

Step 4
Turn the ignition switch off, and plug the electrical connector back to the TPS. At this juncture, you will have to check the TPS for signal voltage to the engine computer. A pin will have to be inserted through the ground wire and another one through the signal voltage wire to do this. Then, connect the voltmeter probes to join the pins with alligator clips, and then turn the engine on.

Step 5
Manually open and close the throttle plate, and take the readings from the meter. Ideally, the voltage has to slowly increase from 1 to 5 volts and back to 1 volt. If the movement of the voltage signal is acting funny (the reading malfunctions in resistance change), there is no change, or there is absolutely no resistance, then you will have to change the sensor.

Step 6
Now, you have to test the TPS resistance. This is an option to test a TPS which is equipped with a variable resistor. Follow that by unplugging the TPS electrical connection, and then set the multimeter to ohms.

Step 7
Manually operate the throttle plate―open and close it, and then check the resistance reading. Typically, the resistance has to increase and decrease slowly as the throttle plate is opened and closed. Again, if there is a huge fluctuation in the reading, you will need a TPS replacement.

Step 8
If the above instructions are not applicable, just try to move and adjust the TPS; this has to be done in some cases, and it may work as well. Loosen the mounting screws with which the TPS has been fixed. These screws help the movement of the TPS for its adjustment. Just adjust or rotate this sensor with the ohmmeter connected.

Step 9
Carry on with the rotation until you get the resistance specified in the vehicle manual, loosening the mounting screws. Then, tighten the screws once you get the required readings. Check the sensor's resistance as mentioned earlier.

Finally, plug the TPS connector again, and then start the engine. Then, see how the car runs. In case you still encounter engine problems, take it to a professional. Remember to refer to the vehicle service manual while doing any of the steps.