... I used the bolt heads used to attach the seat as ground ...
That's okay, but you can also use the battery minus pole.
... While taking these measurements the electronics were very finicky, and I got some weird values ...
… which might also have to do with your meter ... plus, assuming that you‘re using a digital meter, an analog meter is much more comfortable for reading such fluctuating values.
... Let me know if any of these numbers still seem improbable as I may have made an incorrect measurement
These numbers differ significantly form the implausible ones you reported in post 34. … Could it be that in post 34 you measured between both parts of the connector, and not between the o2 signal wire and ground ? …
The numbers you report now, look more plausible and more like what I expected. But you forgot one measurement. Anyway, since these tests are very easily done and you‘re not completely sure if you measured correctly, I suggest to repeat them, with the hot engine running at idle
and the ECU connected
, in the following order:
Closed loop test (EHA and o2 sensor connector connected):
1) Both parts of the o2 sensor connector ‘somehow‘ connected (diagram #1)
Open loop tests (o2 sensor connector not connected):
2) EHA connected (diagram #2 without ground wire)
3) EHA connected and male part of the o2 sensor connected to ground (diagram #2)
4) EHA disconnected (diagram #2 without ground wire)
5) EHA disconnected and engine speed risen to ~ 2500 RPM (diagram #2 without ground wire)