# Trying to find resistance specs for upstream o2 sensor

Nissan Versa 2007. I have repair manual for it, but perhaps I’m too unfamiliar with the manual format. I can’t find the specs for proper ohms across the 2 heater wires for the sensor. It’s the o2 sensor upstream, aka “air fuel” sensor. From internet search, I’ve found that proper ohms varies considerably.by car model, and can’t find anything specific for Versa.

Tester

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Hi Tester. I am trying to do the simple heater resistance test. The link you sent says typical range is 10 to 20 ohms, but I’ve found references online that say some models are much lower, even 2 to 4 ohms. Problem is, I can’t find specs that are specific to the Nissan Versa I’m working on (which is reading about 3 ohms).

Is the Check Engine light on with a O2 sensor heater circuit code?

Tester

No, so then it’s safe to assume current ohms are not out of bounds?

That’s why there’s a Check engine light.

To let you know if there’s a problem.

Tester

Ya know, I kinda figured that’s what they are for!
Just didn’t know (a) whether there was a specific code just for the heater, and (b) how much to trust absence of such codes in general.
In any case, sounds like I should better trust the absence of the code, so I’ll do that.
Thanks for helping to clarify.

Well if you are really board and curios then now would be the time to check it and document the specs so if the code ever pops up you know what the specs are… lol

And for that matter there are a crap load of other sensors you can check out and document the specs on as well…

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Could make a guess of the resistance using the standard electrical formula, power = voltage^2 / resistance. The heater doesn’t need to heat anything big, just enough to heat the sensor, but has to heat it pretty hot, so guessing around 40 Watts. If you think a 40 watt light bulb is about the right amount of heat needed, do the calculations: 40 watts = 12.6 ^2 /R, R = (12.6^2 / 40) = 4 ohms.

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