3- and 4-wire universal O2 sensors
#2
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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.
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.
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#4
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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.
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.