1996 Nissan Maxima SE

[Naoki]

So my engine light went on and lucky me i was doing my work experience at north shore acura so i had them check it out for me
the computer read that it was a knock sensor circuit malfunction and an o2 sensor
now i read that apparently there are 2 downstream o2 sensors and 1 upstream o2 sensor
how would i find out which o2 sensor needs replacing?

[immorality]

Check the voltage output and compare to specs in the factory repair manual.

[Warp9Racing]

you need the code that it reads should be Pxxx and Bx

the knock code is nothing
i believe heated o2 code is front
b1 or b2 is either right or left.

[BoostLover]

Check the voltage output and compare to specs in the factory repair manual.

I agree with immorality. Easiest way. But you need a good accurate volt meter as most systems run half a volt.

[chris_89T]

PM me.

In your y-pipe you have 2 o2 sensors.

Your car should be a federal spec. You have 3 o2 sensors

You have 1 on Bank 1(Firewall side), Bank 2 (front), and one behind the Main cat.

The function of the two Pre cat o2 sensors is A/F control/closed loop control. Those 2 o2 sensors are the ones that will effect the vehicle. The post cat o2 sensors does nothing in terms of performance but strictly for monitoring purposes.

If your replacing the o2 sensor yourself. The bank 1 firewall side connector leads all the way up near the passenger side strut tower. If you stand beside the passenger side wheel looking into the engine bay, on the top of the timing cover just on beside the intake manifold is the connector for that o2 sensor.

For Bank 2 it is directly infront of the radiator, to the right of the dipstick there are 2 connectors one is for the crank position sensor (REF) the other is for the o2 sensor. Disconnect it, they are several clips connecting the harness to the engine mounts so remember to push those back in.

The Post cat o2 sensors harness tucks inside the vehicle behind a rubber grommet. Just pull it out and out comes the connector.

IIRC you should be able to get the o2 sensors out with a 7/8" wrench" Not sure might be 7/8" or 3/4". Alternatively an o2 sensor socket. Soak them with PB blaster or some sort of penetrating fluid first.

Good luck. All the o2 sensors are pretty simple to get too. Shouldnt take more than an hour assuming it comes out with some luck!

[Warp9Racing]

holy fak you work at a dealer or what?

[chris_89T]

On maxima's the knock sensor performs a very important role. A dead knock sensor kills acceleration and fuel economy. It leaves the car in a "safe mode" resulting in less power/poor fuel economy.

The knock sensor code is P0325. The knock sensor is located underneath the plenum in the valley. If you have small hands you can replace it pretty easy. You will need a 1/4" ratchet with a 12" extension, 6" extension and a 12mm elbow.

Without knowing the actual code its hard to tell which one is which. With a good OBD2 reader with live data monitoring you can monitor how much the o2 sensor swtiches back and fourth (between lean/rich), because thats all a narrow band o2 sensor does. If the ECU detects its not switching enough it will trip the code. Generally when o2 sensors get old, they have a tendancy to get "lazy" and will slow down.

Oh and yes, I do work at the dealer, and i owned a maxima!