The O2 sensor is still there and still operational,so it still monitoring things, albeit in a modified fashion. I monitor quite a bit on my rig using the Torque app, and my bank 1 cat runs about 40 degrees hotter than the bank 2 cat; has for quite some time, no difference since the anti-foulers. In any case, I don't have $1000+ for a cat right now, so I will have to take my chances. Thanks for the concern, though; I will continue to watch things closely.

 

As long as the upstreams are operating properly, no need to worry about the cat monitors. You may be sending out a bit more CO2, Yet, not as much as Doc's 442!

Btw, A typical passenger vehicle emits about 4.6 metric tons of carbon dioxide per year.

 

I've had this problem but with the other bank (P0430) for about a year and a half now; light use to come on rarely, now every other startup and I sometimes smell heavy exaust/fuel before the light comes on. I also have pretty terrible fuel economy since this started, 13mpg total is a good number; before the code came on 15mpg.
Any thoughts? I use redline oil, have the GM performance exhaust, new e3 spark plugs, new wires, Ive replaced both down stream O2 sensors, I had several manifold bolts replced to fix a manifold leak; though I still smell exhaust sometimes right before the light comes on. I also installed a catch can with a check valve in the wrong direction and heard a hissing sound and immediately shut the truck off and disconnected the valve (about two years ago) and I did then get abunch of codes, one about evap that went away after clearing them.
I just got a new code the U0190 for the FCPM, repair shop tried to charge me 3.5hrs and $223 for the part with a total just south of $700 ...i am DIYing with the Dorman replacment part (thank you HUMMERZ for your post on this).
So could the FPCM be causing a performance / MPG problem? Only codes I have are these two codes P0430 and the U0190.

 

if you are smelling fuel out the exhaust it could be an injector pissing fuel or fouled plugs or dirty MAF / throttlebody

 

U0190? Replacing downstream 02's does nothing to correct your issue. Check your fuel trims.

 

Wow! Pure coincidence tht my fuel economy droped to 11.5/12 from 15, which happens to be 20 to 25%? Thank you so much. Holy cow, half an hour on you tube and Im confident I can finally fix my ride. Have scan tool, have propane and a hose!

I was pretty sure I had a vacume leak, but no 'mechanic' could find it. They only wanted to throw parts at it. I saw the O2 data plots change on bank2 but not bank1 per rpm but didnt know what todo with this. And now I know about trim (mind blown). Hell I could even feel how the engine would be sluggish the days I didnt floor her and kinda normal when i would; even hesitates the first time I floor it but not the next time(s) ;-)

Ill still have to wait to get the FPCM but hey its like a huge weight off my mind!

 

typo: U0109