How to test a 1 wire o2 sensor

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Oct 28, 2023 | 12:03 PM

Mountain_anderson

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Mountain Pass

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How to test a 1 wire o2 sensor

Hi all, Pulled the o2 sensor out of my 86 f150 5.0. How would I go about testing it to see if it works or not?

Oct 28, 2023 | 12:47 PM

kr98664

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They can be tricky to test, as they need to be at operating temperature. Then the sensor will put out a certain voltage, but we mere mortals have no way of knowing if it is accurate.

Are you getting a fault code pointing to the O2 sensor? If so, the easiest test method is to install a quality replacement and see if the code clears. Sensors are cheap and have a finite lifespan, so I don’t feel bad about loading the parts catapult (Pull!) in this scenario.

Oct 28, 2023 | 01:28 PM

Franklin2

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From: Virginia

Quote:

Originally Posted by Mountain_anderson

Hi all, Pulled the o2 sensor out of my 86 f150 5.0. How would I go about testing it to see if it works or not?

Put the sensor back in. Plug it back in the harness, but make a way to still hook a digital voltmeter to it. Start the engine, and after the engine warms up, you should see the voltage (put the meter on DC scale) swing back and forth between .1volts to .9 volts. .45 volts is midway. If the voltage stays below .45v, the system is running lean. Voltage above .45 is considered rich. The trick is to know if the O2 sensor is working and telling the truth and you have a engine problem causing a lean or rich condition, or the O2 sensor is lying because it's faulty.

If the O2 sensor voltage stays low all the time as in a lean condition, you can take a propane torch that is not lit, hold it near the intake of the engine while it's running, and open the valve on the propane torch. The engine will use the propane as fuel, and you should see the voltage on the O2 sensor go up.

If the O2 sensor voltage stays high all the time, it thinks there is a rich condition. Pull a vacuum line off the engine as it's running to create a lean condition, and see if the voltage on the O2 sensor drops.

Oct 28, 2023 | 01:41 PM

diggerrigger

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From: Evansville, Indiana

Quote:

Originally Posted by Mountain_anderson

Hi all, Pulled the o2 sensor out of my 86 f150 5.0. How would I go about testing it to see if it works or not?

Not on the bench but still in the truck.
You can tap into the one green wire with your digital voltage meter (DVM) while the warm engine is running. Depending on the DVM, you will see either a bunch of different readings bouncing all over but within a range of approximately 0.1v to 0.9v but alternating above and below 0.45v . Or, I have one DVM that just displays an average. In this case a good reading would be approximately 0.45v. It all depends on the refresh rate of the DVM.

Nov 11, 2024 | 02:23 PM

hepok

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Hi, I am sorry for disrupting, i was looking for the way to test one wire o2 sensor on my vitara 1989 1.6 8v, and ended here, i connected red wire to the sensor and black one to the ground and got this, is sensor Ok or not?, thanks

Nov 11, 2024 | 02:33 PM

Max Capacity

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From: Tolland, CT

Quote:

Originally Posted by hepok

I would think yes, as that .754 is in the range, but on the rich side based on the above 2 post.

You may want to try this,
If the O2 sensor voltage stays high all the time, it thinks there is a rich condition. Pull a vacuum line off the engine as it's running to create a lean condition, and see if the voltage on the O2 sensor drops.

The three guys above are some of the "go to guys" on this forum. I've learned a lot from them.