A vehicle's throttle position sensor (TPS) provides very important information to the engine’s computer. The computer uses this data to give the driver more or less engine power as needed. And very often, a driver experiences the effects of a faulty or bad TPS sensor as an engine hesitation or stumbling during acceleration. But checking a TPS sensor’s condition is a very straightforward and easy operation with these simple steps, even if you have minimal knowledge of electrical circuits or just have the desire to learn basic troubleshooting procedures.
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Things you need
- Two pins
Open the bonnet of your vehicle and locate the TPS in the engine compartment. Its most common location is on the outside--to the right or left--of the throttle body or carburettor plate shaft. Here you will see a small black box with three wires coming out from its electrical connector.
Unplug the TPS electrical connector. Turn on the ignition switch, but do not start the engine. Using a voltmeter, probe the connector’s terminals coming from the computer side to test for supply voltage. Touch the negative lead to the connector’s terminal ground--most likely the black wire--and the meter’s positive or red lead to the connector’s terminal reference voltage wire, a blue or grey colour wire. Your meter should read a steady 5.0 volts at the terminal. If you don’t receive this voltage reading, there is an open or short in the supply wire. Turn off the ignition switch and plug the electrical connector back to the TPS.
Test the TPS for signal voltage to the computer. Insert a pin through the ground wire and another pin through the signal voltage wire and connect the voltmeter probes to the pins using alligator clips. Start the engine. As you manually open and close the throttle plate, watch the voltage readings at the meter. The voltage should gradually increase from 1 to 5 volts and back to 1 volt. If you see erratic movement or no movement of voltage signal, replace the TPS. Turn off the engine.
Test the TPS’ resistance. This is an alternate method to test a TPS equipped with a variable resistor. Unplug the TPS electrical connection. Set your multimeter to ohms. Connect the ohmmeter probes to the sensor’s supply and signal wire contacts. Manually open and close the throttle plate and watch the resistance reading at the meter. The resistance should gradually increase and decrease as you open and close the throttle plate. If there is an erratic resistance change, no change, or no resistance at all, replace the TPS.
Adjust the TPS. Some sensors need to be adjusted from time to time. They are mounted with a couple of screws that allow the sensor to be rotated for adjustment. Loosen the mounting screws. With the ohmmeter connected as described in Step 4, rotate the sensor until you obtain the resistance specified in your vehicle service manual. Tighten the mounting screws and check the sensor’s resistance as described in Step 4.
Plug in the TPS electrical connector, start your engine and test for performance.
Tips and warnings
- Consult your vehicle service manual for the proper procedure to adjust the TPS on your vehicle.
- Consult the service manual wiring diagram for your particular vehicle to easily locate components and identify wires. You can buy a vehicle service manual at most automotive parts stores or consult one for free at most public libraries.