vunu

I have a 01 A6 2.8 and got a check engine light indicating a malfunctioning B2 S2 oxygen sensor.

My O2 sensor has a 3 pin instead of 4 pin. (seems a bit odd b/c all autoparts website indicate that 01 A6 has 4 pins, not 3 pins. Can anyone verify this?)

I wanted to replace my current sensor with a universal oxygen sensor that involves reusing the old connector and using a waterproof connection device to connect the old connector cable with the new oxygen sensor.

However, the universal oxygen sensor only seems to come in 4 pins. My understanding of the 4 pins are:

pin1: main signal to the sensor
pin2: ground signal to the sensor
pin3: power
pin4: ground

where as my current(old) sensor has:

pin1: main signal to the sensor
pin2: power
pin3: ground

so, the difference lies in having/ not having the ground signal to the sensor.

My question is, what do I do with the extra line I have on the universal oxygen sensor? do I just leave it hanging? Has anyone found a 3-pin universal oxygen sensor? (there is a 'replacement oxygen sensor' with 3 pins, but doesn't have the 'waterproof connection device')

Thank you for your help.

stoc005

Tie pins 2, 4 of 4 wire O2S to ground. Pin 3 on old sensor wiring.

vunu

O2 sensor
<img src="http://pictureposter.audiworld.com/111747/bos15733003.jpg">

those four wires have their own holes on the waterproof connecting device. The old connector wires and the new sensor wires are twisted and connected inside the device. Well, the extra wire will have no wire to connect to. What's your suggestion? Has anyone used this universal o2 sensor in here?