Originally Posted by Paul1958
Interesting case. Usually when the O2 reading is high (rich) the fuel trim goes negative as the system tries to respond by pulling out fuel. A question would be: is the O2 responding to an issue or is it the issue? The original code you posted P2195 is a lean code.
Well odd thing happened as both the P0171 and P2195 codes have ceased but the P0420 cat converter below efficiency code has appeared. Though since last Thursday have not experienced any additional drivability issues either.
As for the readings maybe the front O2 read low voltage, all I remember for sure is the fuel trim was at +66 when I never generally see it go over +/-10 but fluctuating up and down normally. Maybe I was conflating what I remembered for the fuel trim with the O2 reading. Whichever the case got a front O2 on order as probably near time to change it anyways (has more miles on it than the one I took out when I first got the car).
Last year I got the code for the front cat converter failing and applied an anti-fouler to that O2 but now looks like I will have to do the rear O2 as well.
Interesting case, indeed.