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02 Sensor Voltages

dmcl1980

By dmcl1980,
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QWK32 Veteran

QWK32

Posted
Posted

at idle the O2 sensor signal is a voltage sinewave. it will bounce back and forth between 0v and 1v, well probably more like 0.1v to 0.9v. if your getting constant unchanging voltage from the O2 sensor at idle the sensor is faulty.

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mosquitocoils Veteran

mosquitocoils

Posted
Posted
  lachlanw said:
hold it at 2000 it should bounce from full to low at least 7 times in 10 seconds . if not its a waste of space

Thanks for that mate, I was wondering. Can anyone else verify how quickly it's meant to fluctuate between high and low voltages? I remember vaguely that mine went up and down maybe every second or 2 but sometimes would stick low for a couple of seconds.

dmcl1980 Rookie

dmcl1980

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Posted (edited)

Thanks for that Moodles, very informitave. Going by my PFC hand controller my 02 sensors at idle are showing 1.4v and 1.5v. Reckon they are pretty much fooked. Time to buy some new ones then, doh, cause they aint cheap. I called Nissan Ireland on Friday and was quoted 532euro/864ausd for the 2.

Edited by dmcl1980
wlspn Proficient

wlspn

Posted
Posted
  QWK32 said:
at idle the O2 sensor signal is a voltage sinewave. it will bounce back and forth between 0v and 1v, well probably more like 0.1v to 0.9v. if your getting constant unchanging voltage from the O2 sensor at idle the sensor is faulty.

I have a problem with my RB25 overfueling & generally crap idle... o2 sensor voltage is constant. Cant remember figure...

Is the overfueling likely to be causing the constant voltage or constant voltage causing overfueling?

Unplugged o2 sensor & dont think it made any difference...

mosquitocoils Veteran

mosquitocoils

Posted
Posted
  dmcl1980 said:
Thanks for that Moodles, very informitave. Going by my PFC hand controller my 02 sensors at idle are showing 1.4v and 1.5v. Reckon they are pretty much fooked. Time to buy some new ones then, doh, cause they aint cheap. I called Nissan Ireland on Friday and was quoted 532euro/864ausd for the 2.

That is just plain robbery... they're about 200 AUD here, or I believe 80 to go for a 'generic' brand which works just as well.

Maybe some nice person on the forums would be willing to sell you one?

Moodles2 Grand Master

Moodles2

Posted
Posted

O2 sensors can be tricky, but as long as you know the R32 ECU is designed to use titania based o2 sensors, and R33/R34 use zirconia based o2 sensors. If you have a look at: http://members.pcug.org.au/~jdeakins/facts.html there are cheaper alternatives from NTK you can use as long as you reuse the plug from the old o2 sensors.

  • 11 years later...
dyl33 Mentor

dyl33

Posted
Posted (edited)

May as well post here,

Does anyone know exactly what voltage an rb25det o2 sensor should be at idle?

Should it bounce between 0.2-0.9v like when cruising? Or should it be steady at idle?

Brought a new sensor ntk, the old sensor was stuck on 0.6v at idle, the new sensor sits at 0.85v at idle. AFR at idle is 13.8-14.2 idles fine.

Searched a lot but found varying opinions.

 

Edited by dyl33
dyl33 Mentor

dyl33

Posted
Posted
  On 17/09/2021 at 7:42 AM, Ben C34 said:

Doesn't matter what car, a narrow band sensor functions the same.

Under light cruise and idle should bounce around either side of 0.5 v

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That's what i thought, mine on cruise bounces around and if i give it a little throttle at idle. But just idling it just sits around 0.8. 

  On 17/09/2021 at 10:31 AM, GTSBoy said:

At idle the O2 sensor can be too cold to read properly and may sit at just one voltage and only occasionally do a jitter.

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Even at operating temp? Maybe its normal what im experiencing.

joshuaho96 Veteran

joshuaho96

Posted
Posted
  On 18/09/2021 at 12:34 AM, dyl33 said:

That's what i thought, mine on cruise bounces around and if i give it a little throttle at idle. But just idling it just sits around 0.8. 

Even at operating temp? Maybe its normal what im experiencing.

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As per usual the answer is something unsatisfying which is that it seems to depend. I've taken full Consult logs via NDS while driving the car to work before and you can see that there are cases where you can see with the engine at operating coolant temperature the O2 sensor may slowly oscillate about 0.45V, but it may also drop to basically 0V or something like that which is also totally normal. Here's an example screenshot and one of my drive logs, if you have Nissan Datascan you can look at the full log and zoom in/out at various things. NDS is a great tool IMO, for one it let me know for sure that there's something subtly wrong with my engine idle because the AAC valve barely opens up if ever when the engine is idling with no load while warm. It is very subtly off on the tachometer, enough for me to question if there's really anything wrong sometimes.

image.thumb.png.7e08cf8c36ac40b59cffdc5008779a15.png

2021391529.logFetching info...

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GTSBoy Grand Master

GTSBoy

Posted
Posted
  On 18/09/2021 at 12:34 AM, dyl33 said:

Even at operating temp? Maybe its normal what im experiencing.

Expand  

Absolutely. These are "old tech" sensors and they have integral heaters, but they really rely on hot exhaust gas to keep them at their proper operating temperature. The heater just keeps them closer to the right temperature so that they're always "ready to go" as soon as there is any load on the engine. But at idle the low temperature and low flow rate of gas past the sensor means it will cool down and get lazy, until it eventually just sort of flops around fitfully.

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