i35 O2 sensors

[chasreina]

Hi, I have a 2003 i35 and I need 2 oxygen sensors replaced.
The sensors are bank 2 sensor 1 and 2.

My mechanic is asking for a lot for the parts so i looked online to see if i could get them cheaper.

When i looked online they are described with words like radiator side, firewall side, catalyst inlet outlet, left, right, upper, lower, etc.

I know radiator is front and firewall is back but i am still not sure which sensors i need to buy.

If someone could please clearly explain to me which sensors are bank 2 sensor 1 and 2 that would awesome.

Also i noticed that some are priced around $170 while some are around $50.
Is the price difference just a matter of quality? Is there anything wrong with using the cheaper ones?

Thanks

[loystock]

I just responded to a similar post but for an 00 I30. The part number for the 03 I35 is different.

First, the transverse mounting of the VQ engine places Bank 1 (cylinders 1-3-5) close to the firewall while Bank 2 (cylinders 2-4-6) is close to the radiator. So if you are under the car, the front exhaust pipe is for Bank 2 and merges with Bank 1 exhaust pipe downstream of Bank-1 Pre-Cat (This is where some mechanics may get confused).

Front O2 sensor in general is mounted before (upstream) the catalytic converter while the Rear O2 sensor is mounted after (downstream) of the catalytic converter. As applied to VQ engine, FRONT O2 sensor has 3-wire (power, signal and ground) while REAR O2 sensor had 4-wire (power, signal, ground + dedicated signal ground).

On this particular generation of cars, there are 3 catalytic converters - Bank 2 Pre-Cat (in front of engine) mounted vertically, Bank 1 Pre-Cat (below the engine) mounted horizontally and then the main/rear catalytic converter.

As described above, Bank 2 is towards the radiator. Sensor 1 is visible when looking down at the engine compartment. Just follow the front exhaust pipe and as it goes down, you will see the sensor with BLUE harness (if OEM) and downstream of the Pre-Cat is Sensor 2 with a RED harness. Both connectors are located on the radiator side. It would be advisable to have an O2 sensor adapter/socket (@ $10) to prevent damage to to sensor cable. You can buy NGK or Denso brand for @ $100 for the front and @ $90 for the rear. Front O2 (S1) for NGK is 24618 and 234-3113 for Denso while the Rear O2 (S1) for NGK is 24573 and 234-4241 for Denso. Please go to SparkPlugs.com and call them to verify as I'm very sleepy now.

http://www.sparkplugs.com/results_app.asp

Check Amazon as NGK/NTK brand may be on sale.

[loystock]

Just checked Amazon, both sensors by NGK/NTK are on sale for $70+ each. BTW, avoid the Universal sensor unless you can read wire color coding and knows how to splice wires. They are cheaper but can cause you problem if not done right.

http://www.amazon.com/NGK-24573-Oxygen- ... &carId=002

[Markc]

Since you're a well of knowledge Loystock, may I ask if NTK is the OEM O2 sensor manufacturer?

[loystock]

NTK has always been an OEM-equivalent, not OEM. In the earlier I30s/Maximas, the OEM sensors are made by Bosch (Japan). I'm not sure if that is still the case. Even the layout of the 'cats' and the O2 sensor may have changed but functionally, they should remain the same.

[tibo]

I am also planning to replace the Bank1 O2 sensors in my 2004 I35. Can someone verify the following part numbers: front sensor (upstream) - NGK 24618, Denso 234-3113; rear sensor (downstream) - NGK 24634, Denso 234-4270. Amazon lists the Denso sensors as "OE" style and not the NGK, but Amazon verifies both brands as compatible and will fit the 2004 I35 vehicle.

Will the wiring harnesses of either brand readily fit the connectors on the vehicle. Amazon prices the NGK about a dollar more than the Denso. Does that make NGK a better product than the Denso? Which brand would you recommend?

Thanks.

[maxhopper]

Sorry I missed this. Welcome to NICO.

You can go to http://www.sparkplugs.com and look up your vehicle to verify the part numbers. Any sensor that comes with the harness connector should fit (provided it's the correct sensor). The "universal" O2 sensors have to be wired in to the existing connector.