Post by
loystock »
https://forums.nicoclub.com/loystock-u10145.html
Thu Nov 17, 2011 12:41 am
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 Pre-Cat while the Rear O2 sensor is mounted after (downstream) of the Pre-Cat. 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.
The HO2S2-B1 (Heated Oxygen Sensor, Sensor 2 - Bank 1) is mounted in front of the Bank 1 (as described above) with a WHITE harness and connector on the radiator side. This is a lot easier to replace. The OEM Bosch sensor is13374 @ $120 while an OEM-compatible NGK/NTK is 24574 @ $95. And you're in luck...it's on sale right now at Amazon for @ $66.