Post by
loystock »
https://forums.nicoclub.com/loystock-u10145.html
Thu Sep 17, 2009 12:32 am
Since owners of earlier I30/I35/Maximas (1999-CA, 2000-CA & Federal and beyond) have started replacing O2 sensors, I think it would help you if I clarify some points about the VQ engine exhaust system and related O2 sensors. Please refer to the diagram posted by "maxhopper" earlier. Unless mechanics know your car, they would inadvertently replace the wrong sensor as what happened to "snookhums."
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 Bank1 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 for the O2 sensor location, cable length, original harness color-coding and connector location, see info below:
Bank 1 O2 Sensors-HO2S1-B1: Front 3-wire sensor with BLACK harness, @ 25" long with sensor mounted on the vertical section of the Bank 1 exhaust pipe with connector mounted on top of the engine, rear pax side-HO2S2-B1: Rear 4-wire sensor with WHITE harness, @ 38" long with sensor mounted in front of Bank 1 Pre-Cat and connector mounted on the radiator side
Bank 2 O2 Sensors-HO2S1-B2: Front 3-wire sensor with BLUE harness, @ 11" long with sensor mounted before B2 Pre-Cat (sensor is visible in front of engine) and connector mounted on the radiator side-HO2S2-B2: Rear 4-wire sensor with RED harness, @ 31" long with sensor mounted downstream of B2 Pre-Cat (horizontal section of the pipe) and connector mounted on the radiator side
For most OEM parts, best pricing is from one of NICO sponsors, IoS (Infiniti of Scottsdale) at "infinitipartsUSA.com a.k.a. "everythinginfiniti.com" also "everything nissan.com. They typically have 25% off MSRP.
For best pricing of OEM and quality replacement O2 sensors and spark plugs, it's very hard to beat NGK.com a.k.a. "sparkplugs.com." This is where I usually buy those particular parts. The "oxygensensors.com" referred to by OP is also reputable and in addition to quality replacement parts, also sells Walker and Universal sensors (requires cutting and splicing of wires). If you are patient enough, you can look at eBay (be wary of cheap sensors) and Amazon.com. I was lucky enough to buy an H02S2-B2 (RED) sensor, NGK P/N: 24572, which typically sells from $90-200 from Amazon for $77 including shipping.
Modified by loystock at 12:24 AM 9/18/2009