Oxygen Sensor Wrench

Sbrown said:

Anything is possible, of course. But I think that, unless you have some sort of restriction in your exhaust system downstream of that junction, sprayback is unlikely. I really don't think that's salt on the sensor.

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Thanks! I "read" that you can't tell if they're bad by looking at them, but what do you think?

@ScarabMike Have you seen sensors like these (see earlier post)

Dean P said:

Thanks! I "read" that you can't tell if they're bad by looking at them, but what do you think?

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We normally test them electronically by looking at their output voltage and crosscounts. Visual inspection is not common. If it fails electrically, it fails, it doesn't require a visual inspection to verify. Although we will look at the sensor for evidence of cause of failure to prevent comebacks.

Sbrown said:

We normally test them electronically by looking at their output voltage and crosscounts. Visual inspection is not common. If it fails electrically, it fails, it doesn't require a visual inspection to verify. Although we will look at the sensor for evidence of cause of failure to prevent comebacks.

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Thank you!

Are they three or four wire sensors?


Either way you can use a torch to heat the sensor and measure the voltage output.

the MfM said:

Are they three or four wire sensors?


Either way you can use a torch to heat the sensor and measure the voltage output. One or two wire sensors wouldn’t need to be preheated to bench test.

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Not to be argumentative, but this information is incorrect. First off, you can't bench test an o2 sensor with any sort of validity. Second off, single wire and double wire o2 sensors still have to reach a minimum operating temp (appr 600* F) before they start working. And yes the temp is the same as a sensor with more wires. The sensors with additional wires just have added heaters to get them to temp faster. I would also recommend against hitting an o2 sensor with any sort of torch, due to contamination concerns.

But if someone can find a valid and accepted bench test model, I will happily stand corrected.

(edit) I just did a search on bench testing o2 sensors and I did find a bunch of hits, not one of them would I consider a valid test. Most tests just look at voltage output, none of them look at crosscounts (also known as switching) and a lazy (slow) o2 sensor could pass the bench test voltage test yet still set a check engine light and cause all kinds of running and driveability issues.

I got distracted and your right the last part of my poast makes no sense. I meant to say something about with a 1 or 2 wire sensor you wouldn’t have to worry about figuring out which wires are for the pre heater.

As far as actually testing, I know it’s not 100% accurate but with a torch and a volt meter you can confirm they are bad. If you don’t get any voltage readings or they stay stuck on one reading or are slow to respond then you know they likely need to be replaced. Can also measure the resistance of the pre-heater and compare that reading to the new in the box sensors

I guess I like to confirm, even in a rudimentary way, that parts are bad before I swap them out. I think it’s more important on a boat than a car. Since you might lose a day on the water if the problem is something besides the actual sensor.

I wouldn’t worry about contamination of those old sensors at this point.

the MfM said:

Are they three or four wire sensors?

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Mine are 4 wires.

Thank YOU everyone. I just replaced them both. Like someone said, being on the water is more important. Since I love boating, I replaced them both. Still confused about what all the deposits on the sensors themselves really is. Because, replacing without fixing the problem only prolongs the problem. You keep doing what you're doing, you keep getting what you're getting. If they are original, than I have 2 years before they look like that again.

Dean P said:

You keep doing what you're doing, you keep getting what you're getting.

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That is such a great line!
I'm so stealing it.

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swatski said:

That is such a great line!
I'm so stealing it.

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LOL...you may also like: "Change, does not come from a yes man." One of my favorites.

Interesting fact of the day. O2 sensors can actually "wear out". The voltage they produce comes from a chemical reaction, and at some point you can actually run out of the reactive substance inside, and they stop producing voltage. This is the same reason they need to be at temperature for accurate electronic diagnosis. Typically this is more hours than an engine will see in it's normal lifetime, and failure is usually due to other reasons.

Happy Sunday all!