I was wondering since there are three O2 sensors for our car if there all the same or different part numbers cuz i work at a parts store and can get them cheap so trying to find out for a friend

 

The rear is not the same cuz the rear duz different thingz than the front duz.

 

hmmm.... aren't there two o2 sensors on the max?

and what exactly does the rear do differently than the front? they should both do the same thing -- read o2 levels in the exhaust -- one in the front exhaust bank, one in the rear exhaust bank.

 

there are 3 total.. the front 2 are exacty the same the rear is different because its just a reference..

 

ok, why are there two o2 sensors in the front and only one in the rear?

also, could you explain what you mean by "the rear is different because its just a reference"?

thanks.

 

Simply put...

The 2 up front monitor the a/f and tell the ECU to adjust fuel trims accordingly. The reason there are 2 is because the VQ is a "V" type engine which requires 2 banks to operate(hence the symetrical fashion of the letter "V") , therefore needing 2 o2 sensors to monitor each bank via the exhaust manifold located just after each head.

The rear sensor is in the exhaust pipe after the cat, and since Maximas did not come with dual exhaust, there is only one pipe after the y-pipe. This bad boy monitors the condition of the catalytic convertor, and has no say so re: A/F.

 

The two in the front are mounted in the Y-pipe and the sensor in the rear is mounted in the cat.

 

There are three, 2 in the front and 1 in the back!

 

No shit sherlock.

 

thanks for the info guys. i see now.... 2 o2 sensors -- one for each bank, plus one additional one after the cat. didn't realize the cat had one.