rear o2?

[Michael Jez]

Rear O2 is used for Cat efficiency, if it sees a problem it will flash a
code saying its got a problem with the cat or itself. Usually the code will
be like Catalitic Converter efficiency below threshold or something alike-
from my Hyundai dealer experience where I repleaced ALOT of cats.
I would hold the engine at around 2500RPM and watch the voltage reading
change from rich to lean back and forth pretty fast, it it stays at once
spot or another for too long, U got a dud. Front 02 is used for emissions
and MPG and shit alike, where the rear is used for cat monitoring only. I
would also check the MAF for proper ground and alike.
Mike Jez
93 SE-R one O2 sensor...uhh whats a cat ? GTi-R powered beast TO4E.
01 Max with 4 O2 sensors, 3 cats- only one on the car at the time :) whoppin
30HP mod I swear at the wheels.