02 voltages

[Brahmajoe]

Does anybody know what normal operation 02 sensor voltages should be? V6 pentastar

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[OHJeeper]

I'm pretty sure all O2 sensors (maybe except wideband?) operate at 0.1 - 1.0 V. Are you seeing fuel/air issue you're trying to track down?

 

[Brahmajoe]

I had a z60 recall done for rough idle no flash needed but second step is to check o2 sensors..just an inkling they didn’t so I wanted to check them with JScan

 

[OHJeeper]

Got it!

So, please don't take this the wrong way: based on your original question, I'm guessing you have not done this before? For the moment, I'll assume you haven't.

It's not as simple as measuring the voltage (it's not constant). There is a switch from low -> high -> low, like a sound wave if you graph it, that corresponds to the A:F mixture at any given time. Those voltages tell the ECU if there's too much air or too much fuel and the ECU compensates to get it "right". Those voltages affect 2 main metrics: STFT (short term fuel trim) and LTFT (long term fuel trim)

I would do a search on YouTube on "Short Term Fuel Trim" for a detailed explanation, as well as how to test it.

Sorry if you already knew all this!

 

[Brahmajoe]

Thanks for the help. I’ve changed out 02 sensors but I believe we have 4 and I’ve seen people having issues with the upstream passenger side do to oil leaks out of the pcv

 

[Brahmajoe]

I just wasn’t aware if at idle I should see base voltages and if a threshold was off I can say ahhh I have to change this one out

 

[OHJeeper]

Yes, we have 4... ignore the downstream, they have no bearing on A:F trims. They are used only to gauge cat efficiency. In fact, their behavior is not even the same as the upstream - they will peg rich once the cat's are heated up and not cycle like the upstream O2 sensors.

 

[OHJeeper]

I just wasn’t aware if at idle I should see base voltages and if a threshold was off I can say ahhh I have to change this one out

Nope, at idle (after the coolant warms up) you should also see the fluctuation.

And if the voltage is out of range, you'll get a CEL. And, if it doesn't move at all (stays constant) you should also get a CEL.

 

[Brahmajoe]

So most likely no check engine light they are functioning

 

[OHJeeper]

most likely... usually using the O2 sensor readings is to help diagnose something else in the air/fuel chain of events (pumps, throttle, intake, vacuum leak, etc). It's pretty rare you'll find a bad O2 sensor with a scanner that the PCM hasn't already picked up.

But, you can hook up JScan and graph the O2 sensor voltages for piece of mind. The curves won't be smooth unless you have a high-end OBD adapter or oscilloscope, but if you see voltage rising/falling and no CEL, then you're in good shape.

 

[ShadowsPapa]

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