The throttle position sensor (TPS) is a super easy component to test on the 2.2L Chevrolet S10 and GMC Sonoma.
You don't need any expensive testing equipment to do it, and in this tutorial, I'll show you how to test it with a multimeter.
With your test results, you'll easily and quickly determine if the TPS is good or bad.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1994-1997 2.2L Chevrolet S10, GMC Sonoma) (at: autotecnico-online.com).
APPLIES TO: This tutorial applies to the following vehicles:
- 2.2L Chevrolet S10: 1994, 1995, 1996, 1997.
- 2.2L GMC Sonoma: 1994, 1995, 1996, 1997.
- 2.2L Isuzu Hombre: 1996, 1997.
Symptoms Of A Bad Throttle Position Sensor
No doubt you're already aware that the accelerator pedal is connected to the throttle plate via a cable.
So whenever you step on or step off the accelerator pedal, the throttle plate opens or closes to allow more or less air into the engine.
The fuel injection computer needs to know the throttle plate angle so that it can inject more or less fuel.
And as you've guessed it, the component tasked with this job is the throttle position sensor. So when this bad boy fails, the fuel injection computer is definitely going to resent it.
You'll see one of the following TPS diagnostic trouble codes illuminating the check engine light when the TPS fails:
OBD I equipped vehicles:
- Code 21: Throttle Position Sensor (TPS) Signal Voltage High.
- Code 22: Throttle Position Sensor (TPS) Signal Voltage Low.
OBD II equipped vehicles:
- P0121: Throttle Position (TP) Circuit Performance Problem.
- P0122: Throttle Position (TP) Circuit Low Input.
- P0123: Throttle Position (TP) Circuit High Input.
You'll also see one or more of the following symptoms:
- Hesitation when accelerating the engine.
- Lack of power.
- Bad gas mileage.
Where To Buy The TPS And Save
The throttle position sensor isn't an expensive component, still it doesn't hurt to save money and here are recommendations of known automotive brands (avoid knock off sensors).
Not sure if the above TPS fits your particular vehicle? Don't worry. Once you get to the site they'll make sure it fits by asking you the specifics of your particular vehicle. If it doesn't fit, they'll find you the right one.
TEST 1: Testing The TPS Voltage Signal
To successfully test the TPS, it's important to know that it produces a voltage signal that increases as the throttle plate opens and decreases as the throttle plate closes.
The cool thing is that you and I can verify if the TPS voltage signal is increasing/decreasing with a multimeter.
This test section focuses on checking the TPS voltage signal as you manually open/close the throttle plate.
If the throttle position sensor is bad, you'll usually see the TPS voltage stuck in one value as you open/close the throttle plate.
The wire that you'll connect your multimeter to is the blue (BLU) wire of the sensor's three-wire connector. I've labeled it with the letter C in the photo above.
NOTE: You'll need a multimeter to be able to test the throttle position sensor. If you don't have one, check out my recommendations here: Buying A Digital Multimeter For Automotive Diagnostic Testing.
OK, let's start:
PART 1:
- 1
Turn the key to the ON position but don't start the engine.
- 2
Place your multimeter in Volts DC mode.
- 3
Connect the red multimeter test lead to the blue (BLU) wire of the TP sensor harness connector.
The BLU wire connects to the terminal identified with the letter C in the photo above. - 4
Connect the black multimeter test lead to the battery negative (-) terminal.
NOTE: The TP sensor must remain connected to its electrical connector. You'll need to use a back probe or a wiring piercing probe to tap into the signal of the middle wire. To see what a wire piercing probe looks like and where to buy one, go here: Wire Piercing Probe. - 5
Your multimeter should report a voltage between 0.2 to 0.9 Volts DC with the throttle plate closed.
If your multimeter doesn't, don't worry about it just yet, continue with the other steps.
PART 2:
- 6
Slowly open the throttle plate (by hand from the engine compartment).
- 7
The voltage value should increase as the throttle plate opens.
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. - 8
Slowly close the throttle plate.
- 9
As the throttle plate is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the same voltage you noticed in step 3.
PART 3:
- 10
Lightly tap on the throttle position sensor with the handle of a screw-driver or something similar (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. - 11
Repeat step 10 several times to make sure of your multimeter test results.
Let's take a look at your test results:
CASE 1: The TPS signal voltage increased/decreased as you opened/closed the throttle plate. This is the correct test result and it lets you know the TPS is functioning correctly.
You can also conclude that the TPS is receiving power and Ground. No further testing is needed.
CASE 2: The TPS signal voltage DID NOT increase/decrease as you opened/closed the throttle plate. This test result usually tells you the TPS is bad.
To be sure the TPS is bad, you need to make sure it's getting power and Ground. Go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.
CASE 3: The multimeter DID NOT register any voltage.
Go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts. This test result usually tells you the TPS is bad.
To be sure the TPS is bad, you need to make sure it's getting power and Ground. Go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.
