# O2 sensor Multimeter tests



## The_Criz (Sep 28, 2009)

I'm in the middle of troubleshooting the infamous P0430 DTC on my 2001 Maxima - all stock exhaust & engine. I've run both the bank 2 O2 sensor with my multimeter and I'm getting some readings that are a bit odd:

Upstream O2 sensor doesn't modulate from .1V to .9V, it pretty much just sits there at .4V The downstream O2 sensor does pretty much the same thing. This is after I've let them warm up as well.

The oxygen sensor heater resistance is 4.9 ohms, which (according to the repair manual I have) is just outside the allowed range of 2.3-4.3 ohms. But this is the same reading on all the O2 sensors - bank 1 and 2. So I'd be expecting a P0420 as well?

So I'm guessing my literature is either outdated or wrong. Does anybody have the official (correct) O2 sensor specs?

Little help.


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## The_Criz (Sep 28, 2009)

*Got it.*

Found a link in the forums around here (really great site btw) and got the official Nissan troubleshooting manuals.

Turns out I needed to be testing from the ECM harness vs. the O2 connectors. Test by using a voltmeter attached to the ECM pin on the + and clip the - to a ground.

For the benefit of anybody who is in my position, here's what I was able to find out:

ECM pin 62 & 71 = Bank 2 O2 sensors.
ECM pin 63 & 72 = Bank 1 O2 sensors.

pins 63 and 62 are the upstream sensors. These should switch between low (0.0-0.3V) and high (0.6V-1.0V) more than 5 times in 10 seconds after the car has been warmed up and is running at 2000rpms w/ no load.

pins 71 and 72 are the downstream sensors and they should be sitting somewhere around 0.4V. It should stay below 0.54V for a least a short time. 
Rev the engine to 4000rpm with 10 quick bursts and you should see it jump over 0.54V at least once.

After all this, take your measurements and use the ratio of A/B with:
A=downstream sensor reading
B=upstream sensor reading

You should be less than .75 with anything above that triggering the P0430 or P0420 DTC codes.

I hope this helps those folks like me looking for this info.


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