[Shotimes] O2 sensor question

[Jeremy Brown]

You're pretty much right - the sensors before the cats are the ones 
that affect your fuel trims.  The ones after the converters are only 
there to check for proper catalyst operation - they are not used for 
engine calibrations.


-Jeremy
94 Opal ATX (Dead, pff!)


> Generic question regarding O2 sensors.  Sending to both lists since
> the Gen3 is OBD-II.
> 
> Can someone explain what the different O2 sensors do?  As far as I 
can
> tell on every OBD-II car there are O2 sensors both before and after
> each catalytic convertor.  Is one there for emissions purposes only? 
> I know the with Ohio's E-check emissions testing there is now a 
simple
> OBD-II plug-in test, but can't figure out how all this works.
> 
> Also I'm guessing that if there is a fuel mileage problem that's O2
> sensor driven that the culprit would likely be the sensor before the
> cat.  Correct?
> 
> Anyone who knows please fill me in.  Inquiring minds want to know!
> 
> Thanks,
> 
> Steve Tatro
> Red/Black '93 with 181k miles
> Monroe, Ohio