ultragauge shows my p5 stuck in open loop.

[Installshield 2]

weird stuff for sure...

I'm a little lost as to the readings from the 2nd o2 sensor...i'm positive the first o2 sensor is whats used for AFR trimming...and that makes sense...the system wouldn't work correctly if a reading was being taken from the second o2 sensor, after the catalyst, to adjust fuel requirements...as the catalyst itself is there to 'reburn' any residual fuel and oxygen...So the 2nd o2 sensor never knows if the fuel was burned properly in the chambers, or in the catalyst...right?

the fluctuation after start up on the 1st sensor makes sense...its actively reading whats being burned in the engine, with no worries as to what the catalyst does...the 2nd sensor being stable during a cold start makes sense also...the computer probably ignores it, as its been programmed with the fact that a catalyst will not do a single thing until its fully heated...so there is no point in switching the 2nd sensor on until things are starting to heat up...

then...shat gets weird...but i think you're looking at it backwards, possibly...the 2nd o2 sensor is slightly changing output BECAUSE the primary o2 sensor is adjusting the mixture (that is why its changing wildly)...not the other way around...The primary sensor sends an output for mixture adjustment, the computer does it, the engine burns it, and the 2nd o2 sensor might see some temporary changes because of that alone...again, we're pretty confident the 2nd o2 sensor has no use other than catalyst checks...

one thing to try, just to see what happens to the 2nd o2 sensor readings...is go to a auto parts store and buy the spark plug non-foulers...drill the one out (they're aluminum, its easy) to fit the 2nd sensor...then mount it back in your exhaust system...this 'hides' the 2nd sensor from reading any oxygen ppm...and see if your primary o2 sensor still fluctuates the same, and if the 2nd sensor fluctuates at all...in these conditions, the 2nd sensor shouldn't move voltage wise...as its not actually reading any exhaust stream contents...but its mounted in the system enough to still get hot (the other check the computer performs)...

if it does still move around...i'm totally lost...but more importantly, i don't think this is anything to worry about in either case...

 

[pcb]

Yea I don't think it matters,... I'm just curious. If I try the non-fouler thing, I'm gonna wait till spring.

The one observation I made (however backwards it might be) was when the car was fully warmed up and I went WOT in 5th gear starting at about 1500 RPM. Both O2 sensors were steady at 0.915 (perhaps the map setting) then the second O2 went up only to 0.920 then the first O2 went right down to 0.300 or so and bounced around at a lower number until the second O2 returned to 0.915 V then the first O2 returned to 0.915 and both stayed there until I was going way too fast for a gravel road (and also below that 3100-3300 rpm switch over point). All that really looks to me like the first O2 is reacting to the second O2 to provide a stable reading. I think our car may be an odd duck, according to Ultra-Gauge every car (except diesels) will read closed loop. That and our car I guess.

Another thing I just realized, how can both O2 sensors read the same voltage if one is before the pre-cat and the other is after. The pre-cat must be doing something to affect the value unless it's "saturated" or the voltage scale is different on the two O2 sensors.

I was wondering if O2 sensors get old and wear out slowly or if they completely fail,.. Good one day, broken the next.

Do I have to tap the end I drill out on the non fouler?, I don't think I have a tap that big. (I assume it's similar to a spark plug thread)

 

[Installshield 2]

yeah man, i'm not sure whats up for the most part haha...

As far as the voltage outputs...I think you're right, and that they are possibly scaled differently...from what i've read, the 2nd sensor has some useless resolution (the voltage will go up and down with some accuracy..as apposed to just 0v, 1v, etc...)...but the ECU only cares about a threshold...meaning if the voltage hits some predetermined value, it takes that data as the catalyst not working properly...and pops a code...

so even though the voltage number is all over the place on that 2nd sensor...the ecu doesn't particularly care...

 

[pcb]

OK,.. I've officially decided to not care.

I finally found the non-fouler how-to,.. that makes sense now.