After a lot of thinking, reading field service manual and swapping sensor parts because of a good rust bucket source, I'm sure I want to replace my thermal sensor. I'm aware a SR20DE engine has two thermal sensors but the sensor for the fan is okay because fan switches on.
The other sensor is used by the ecu to decide what kind of mixture is needed, especially in open loop (where lambda readouts are omitted, warming cycle).
My SR20DE is stuck in open loop, ecu thinks engine is warming up but never reaches closed loop (warmed engine)
This sensor is just above the oil filter but not reachable with common tools.
Could someone tell me how to reach it and loosen it? If that is done I can easily remove the Nissan stlye connector (with the metal pin that needs to be rised) and put in a known good (new) thermal sensor so I can start real fault searching (solving bad fuel economy).