This one is for the gearheads. I’m trying to get info on how the O2 sensors operate specifically for the N14. I’m getting conflicting information so I wanted to see what comes up here. Here are my questions.
1) At start, with cold engine, how do both sensors operate? As I understand it they operate in “open loop” mode until engine heats up then go into closed loop mode. But I believe the mini has a heated o2 sensor, so does this mean it’s different? What voltage should read at start with cold engine?
2) After engine warms up what should voltage read for each sensor? How should they fluctuate in voltage? Or does one fluctuate and one stay consistent?
3) So we have open loop and closed loop but there is also open loop fault (stuck open) and closed loop fault (stuck closed). What’s the difference? Specifically looking at closed loop fault. What typically are the causes of this? Is it just a bad sensor or is the ecu telling the sensor to do this because of some other issue? If so what could those issues be?
Any answers are appreciated. Or if anyone knows where I can find published material that goes into detail on the operation of the O2 sensors specifically for N14 I would greatly appreciate it.