- Clean The Throttle
Before diving into your throttle position sensor with a multimeter, you have to take some preliminary steps.
One of these is to clean your throttle, as it could be the debris on it that prevents it from opening or closing properly.
Disconnect the air cleaner assembler from the throttle position sensor and check the throttle plate and walls for any carbon buildup.
Dampen a rag with a carburetor cleaner and wipe away any debris where you see a build-up of it.
Once you have done this, ensure the throttle fully opens and closes properly.
It’s time to move to the throttle position sensor.
These wires or connector tabs are important for our tests.
If you’re having trouble finding the wires, see our guide on how to trace wires.
Check the TPS wires and terminals for damage and a build-up of dirt. Take care of any impurities and proceed to the next step.
- Locate The Throttle Position Sensor Grounding
Finding the throttle position grounding determines if you have a problem and also helps with subsequent tests.
Set your multimeter to the 20 DC voltage range, turn your ignition to the “on” position without starting the engine, and then place the red positive probe on the positive car battery post (tagged “+”).
Now, place the black negative probe on each of the TPS wire tabs or terminals.
You do this until one shows you a reading of 12 volts. This is your ground terminal and your TPS has passed this test.
- Find The Reference Voltage Terminal
With your car ignition still in the “on” position and the multimeter set to the 10 DC voltage range, place the black lead on the ground TPS terminal and place the red lead on each of the other two terminals.
The terminal that presents you with about 5 volts is the reference voltage terminal.
If you don’t get any 5-volt reading, then there is a problem within your TPS circuit and you may check for loose or corroded wiring.
Connect the wires back into the throttle position sensors and move to the next step.
- Test The TPS Signal Voltage
The signal voltage test is the ultimate test that determines if your throttle position sensor is functioning properly or not.
It helps to diagnose whether the TPS accurately reads the throttle plate when it is fully open, halfway open, or closed.
Set the multimeter to the 10 DC voltage range, place the black probe on the ground TPS terminal, and place the red probe on the signal voltage terminal.
In this case, you use pins to back probe the wires (poke each TPS wire with a pin) and attach your multimeter probes to these pins (preferably using alligator clips).
The value displayed depends on the model of your TPS.
If the multimeter shows a reading of zero (0), you may still proceed to the next steps.
Gradually open the throttle plate and watch how the readings on the multimeter change.
Your multimeter is expected to display a steadily increasing value as you open up the throttle.
When the plate is fully open, the multimeter is also expected to display 5 volts (or 3.5 volts in some TPS models).
The TPS is not in good condition and needs to be changed if you experience the following:
- If the value massively skips while opening the plate.
- If the value gets stuck at a number for a long period.
- If the value doesn’t reach 5 volts when the throttle plate is fully opened
- If the value inappropriately skips or changes when you lightly tap the sensor with a screwdriver
All these are representations of a TPS that needs to be replaced.
However, if your throttle position sensor is an adjustable model, like those found in older vehicles, then there is more to do before deciding to replace the sensor.
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