Do the upstream 3 wire oxygen sensors send a variable signal or is it simply a shut off and on switch. i.e, I appreciate that it effects the rich lean direction from the ECU, but is it a wide band of mixture options or a very simple one? Also, do the sensors either work and not work or can they vary in efficiency?

 

Variable signal
It can simply fail
They can vary in efficiency as they age causing poor performance/MPG

 

+1....the upstream sensors are variable signal. When they go...you'll know it becuase your gas mileage will suck completely.....and you'll have a CEL.

I suppose they can vary in efficiency, but most wont realize the slight degradation in performance until it finally dies.

 

for the sake of starting a new thread one of you guys could help me out in the o2 section i just got code p0136 rear 02 and my car has a rough idle the needle dosent show it but you could feel it when just idleling or taking off should i replace the rear o2?

 

The post converter O2 has nothing to do with how the car idles.

 

after reading ur post i went out n hooked up the obd scanner n i got code p0303 cylinder 3 misfire could the 02 sensor have something to do with this?

 

The rear O2 sensor has nothing to do with anything, it just determines whether or not the converter is functioning properly.

You'll have to diagnose the misfire.

 

hey pmohr u got a pic of the Engine Control Harness i want to diagnose the fuel injectors but i dont want to take the manifold off n finding out it wasent an injector

 

A picture of what, exactly?

 

i read on the org that if i wanted to test the rear fuel injector i dont have to remove the manifold i could just locate the harness that is shape like a v i try looking for it but the discription doesent really help much

 

Hi,
From france, this is my first question !

On my EU Maxima SE 95 with a "small" VQ20DE engine, with only two upstream O2 sensors (Not downstream O2 sensor after cat), i have on the second sensor (just before cat) a permanent voltage of 1,42 v when i test on the middle wire of the connector. Is the sign of a failed O2 sensor ?

The first sensor has variations between 0,00v to 0,85v

Thank you a lot in advance and excuse me if my english is poor !

 

Your ECU should be kicking out a code if any o2 sensor is out of range or not working. They do expire. I don't know the ohm or v range, but you should be able to tell if you have poor gas mileage. It would be worth your while to get an aftermarket 02 off of eBay, mine cost $20 and works fine. I used some heat shrink to seal the joints and used the old oem adapter at the input. Then just reset the ecu with a screwdriver. You may also need to borrow or buy an 02 ratchet socket to get the old sensor out, but sometimes you can just cut the wires and put a stock long socket over it.