I know I have four O2 sensors and I have readings from all of them after a 30 mile drive. I used AutoEnginuity scan tool to save the reading to a CSV file for playback. If you want a copy to see what is going on just let me know.

What I don't know is;
What are the readings meant to be?
Does speed affect the readings?
ShouldBankone front and bank two front have the same readings?
Should bank one rear and bank two rear have the same readings?
Is there a maximum and minimum range that they should work in?
Does the Mass Air Flow sensor affect the readings, if so, how?

I am sorry guys, I have a million questions on this and would really love to learn how it all works.

The reason this all started is because I had left and right lean errors so I cleaned the mass air flow sensor. OMG what a bloody difference, idle is wonderful, performance is fantastic, AND gas mileage has shot up

Thanks for reading guys and all input is appreciated.

Mark

 

I will keep this as simple as possible. The upstream(before cat) o2 sensors are there as a final fuel trim meter. After the more important readings from the mass air, manifold absolute pressure and coolant temp sensors are used to determine fueling levels the upstream o2 sensors check the accuracy of those results and if the readings aren't where the ECM wants them fueling will be altered to get them in spec. The upstream sensors are also used to determine function and efficiency of the EGR system on vehicles that have that. The readings should be similar but not exactly the same from bank to bank. If you have looked at a lot of o2 readings it becomes pretty easy to determine problems with the sensors themselves. This is why o2 codes are commonly misdiagnosed. Just because you have a lean exhaust code for o2 sensor bank 1 sensor 1 this doesn't mean there is anything wrong with the sensor. It could very well, and most commonly, be something wrong upstream from the o2 sensor that has caused the sensor to go beyond its useful range which causes the code to be set. Now, if you have an o2 sensor heater code that's another matter and checking of the heater circuit is warranted.

The downstream o2 sensors are there for 1 purpose only, to test the efficiency of the catalytic converter and are not used in fuel trim.