I have 96 I30 and it looks like the oxygen sensors are bad. Two weeks ago, I had check engine light cleared, now, it came back. Even worse, I can feel the mileage is bad. Went to AutoZone today, they said I need one front and one rear for 79.99 each. Then I call advanced autopart, they told me there are two front sensors and one rear sensor. On http://www.oxygensensorwholesale.com..._1996_i30.html, it lists four oxygen sensors for this car. I am confused now. How many O2 sensors does car have? Is it easy to replace them?

Thanks for your advices.

 

I believe there are three oxygen sensors. One is in the front, sort of visible from the hood, another is closer to the firewall, and the third is in your cat.

Oxygen sensors affect your emissions and nothing else. That being said, if you are noticing bad mileage it shouldn't be a result of a bad O2 sensor, it's probably something else. There's no reason to put off replacing it, but the only time it is absolutely necessary (as far as I know, and I could be wrong so someone else can feel free to correct me) to replace it is when you are getting an inspection where your emissions will be tested. I don't know if it is the same in your state as it is here in MA, but emissions are tested every other year during an inspection, or upon transfer of ownership or re-registering the vehicle.

As far as I know, it is fairly easy to replace these sensors though I have never done it myself. I think for at least one of the sensors, you may need a jack or something because it is hard to get at. Also, try to find out which sensors you need, you might not need all three though many people replace them all at the same time regardless. Good luck!

 

3 sensors total, 2 fronts and 1 rear.
and like infinitishock said you should find out which one(s)

 

3 total. one on each bank of the y-pipe and one on the cat. I doubt they are all bad. Just replace the ones that are bad.

A bad o2 sensor can affect gas mileage. But it will not effect performance in open loop operation (throttle above 50% of so). It will only affect the car in closed loop operation. That is the only time that the ECU uses the o2 sensors to adjust the air fuel ratio.

The front 2 sensors are fairly easy to replace. If you have an aftermarket y-pipe they are even easier. I suggest getting the OEM replacement ones from oxygensensors.com

 

Screw was in the wrong spot

 

Ok, as I understood there are three sensors on this car, two are in front of catalyst converter, one after it. Using OBD scanner, I got P0130 (front O2 sensor, bank 1), P0136 (rear O2 sensor, bank 1) and P0325 (knock sensor). which is which? I am still confused. Should I replace both sensors in front of catalyst converter, or the one after it and one before it? Please advice.

 

you need to change one of the front o2 sensors and the rear o2 sensor that is on the cat. Don't mess with the knock sensor until the o2 sensors are fixed, the knock sensor code may go away

 

I got a "Bank 1 Sensor 2". Is this the one on the left of the y-pipe or the right?

 

I believe bank one is the rear bank. Left or right is subjective to how you look at it....the rear bank is the part of the y-pipe that goes to the rear manifold.