The throttle position sensor on your 2.4L Nissan Frontier (XTerra and Pick Up) is two sensors is one. One part is the throttle position sensor. The other part is a throttle position switch.
In this tutorial, I'll show you how to test the throttle position sensor part.
Contents of this tutorial:
If you need to test the idle switch part of the throttle position sensor, this tutorial will help: How To Test The Idle Switch (2.4L Pick Up, Frontier, Xterra).
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS Con Multímetro (2.4L Pick Up, Frontier, Xterra) (at: autotecnico-online.com).
Symptoms Of A Bad Throttle Position Sensor
A bad throttle position sensor on your 2.4L Nissan will set a trouble code and light up the check engine light (CEL). Here's a brief list of symptoms you'll see with the TPS fails:
- Check engine light (CEL) shining nice and bright.
- Diagnostic trouble codes (DTC) stored in the PCM's memory:
- P0120: Throttle Position Sensor Circuit.
- Your 2.4L Nissan Frontier (Xterra or Pick Up) fails the state mandated emissions test.
- Bad gas mileage.
- Hard start and/or extended cranking time (after shut off).
- Black smoke coming out of the tailpipe.
- Hesitation when accelerating your vehicle down the road.
TEST 1: Testing The Throttle Position Sensor Voltage Signal
The very first thing we'll do, to see if the throttle position sensor (TPS) has failed or not, is to see if it's creating a throttle angle voltage signal.
We'll do this by tapping into the wire of the TP sensor connector that carries the throttle angle voltage signal to the PCM with a multimeter.
To help you in identifying the correct connector: The throttle position sensor connector has 3 wires sticking out of it. The throttle position switch connector has 2 wires coming out of it.
The illustration above will help you identify the correct connector to test since the throttle position sensor assembly has two connectors.
NOTE: The throttle position sensor has to remain connected to its connector for this test to work (this is where a wire piercing probe comes in handy to get to the signal inside the wire. To see what one looks like, click here: Wire Piercing Probe Tool).
OK, let's start:
Place your multimeter in Volts DC mode and with the red multimeter test lead probe the middle wire of the sensor's connector. This is the wire that connects to pin #2 in the illustration above.
Ground the black multimeter test lead on the battery negative (-) terminal. Have your helper turn the key ON, but don't start the engine (this will power up the TP sensor).
Your multimeter should report a voltage between 0.2 to 0.9 Volts DC. If your multimeter doesn't, don't worry about it just yet, continue with the other steps.
Now, slowly open the throttle (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.
For this test result to be accurate, you need to open the throttle by hand and not from inside the vehicle.
As the throttle opens, the voltage numbers will increase. This increase in voltage should be smooth and without any gaps or skips. Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC.
Now, slowly close the throttle. As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 4.
OK, now you'll need someone to help you lightly tap on the throttle position sensor with the handle of a screw-driver (or something similar, and I want to emphasize the words 'lightly tap') as you slowly open and close the throttle and observe the multimeter.
If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers.
Repeat step 7 several times to make sure of your multimeter test results.
Let's take a look at your test results:
CASE 1: The multimeter showed the voltage value increase then decrease as you opened/closed the throttle plate. This test result confirms that the TP sensor is OK and not defective.
CASE 2: The voltage value DID NOT increase or decrease as you opened/closed the throttle plate. This tells you that the TP sensor is bad and needs to be replaced.
If I where in your shoes, I would still make sure that the TP sensor is getting both power and Ground. To check for power, go to: TEST 2: Verifying Throttle Position Sensor Has Power.
CASE 3: The multimeter DID NOT register any voltage. This test result doesn't condemn the TP sensor as bad just yet. Why?
Because the TP sensor may be missing either power or Ground. So the next step is to check that the TP sensor is getting power, go to: TEST 2: Verifying Throttle Position Sensor Has Power.