Mark944na86

What's the difference between the 3- and 4-wire versions of the universal O2 sensors?

-Mark 86 944 NA

Michael Stephenson

The 3-wire O2 is grounded through the exhaust system. The exhaust system changes resistance as the temp of the piping changes, thus making the O2 sensor readings somewhat variable. The 4-wire O2 has its own dedicated ground wire, which when run to the negative terminal of the battery eliminates the variable resistance issue encountered being grounded to the exhaust.

In theory, the 4-wire sensor is more accurate. Does a 4-wire O2 sensor really make a difference? I do not know, but I have one.

Mark944na86

Was the 4-wire sensor standard equipment on the S2, or did you retrofit?

-Mark 86 944 NA

Michael Stephenson

It was a retrofit.

I had this great idea that running a Air/Fuel meter would be a good thing and in researching I had some listers mention that the 4-wire was the way to go. (The Air/Fuel thing did not turn out as I expected.)

Anyway, if you go this route, try really hard to find a connector that fits the 4-wire sensor. Attach that connector to your harness. I cut off my connector and hard wired it - it was messy and it will be difficult to replace the sensor in the future. Had I the foresight to wire in the proper connector to the harness (which I will do next go round), I would just have to unplug it and pop in a new sensor.

MadMax

Michael,
What is the part number and where did you get your O2 sensor? How much was it?

Regards,
Max

Skip

13225 - Bosch 4-wire Universal

I can only guess where he got it...