We used to inventory more higher mileage vehicles than we do now which meant that we had to deal with more O2 sensors. I always kept a number of O2s on the shelf that I had pulled from the pick-a-part yards. All we really had to deal with were the 4 wire narrow bands. There were basically 2 brands; one with the round end on the shield and one with a flat end on the shield. Often they would interchange and work, no problem. But occasionally for what ever reason, a vehicle would not like anything but the style it came with. So, I would usually replace an O2 with the same style that came out of it. Wasn't usually necessary, but since I had a handful to choose from, it just ensured that I wouldn't need to revisit it.

And being used, I always tested them before installing them. They needed to swing through their voltage range very quickly, and needed to hit at least .9v. Preferably, a full 1v. The connectors were usually different from one car to another so it would need to be changed. And although the sensor itself was usually the same, downstream O2s usually had much longer leads.

I also used the narrow O2s in a tail pipe fixture that I had made with a meter to set the cruise on some of my buddy's carbed stuff. Probably like the fixture that was mentioned in an earlier post. It was good to get the cruise in the mid 14s. Every Holley that I have checked has been way rich on the cruise, often 4 jets sizes or more.

Because of our change in inventory, I don't see much O2 trouble codes anymore. Now it's TPMS. So, I carry a scan tool and pull them at the yards so that I can keep them handy. It's always something.