over the winter i blew my 320k 5sfe in my camry...so i went in search of a replacement motor to go with my 80k 5-speed. i wound up with a 120k fed motor. i then began to see the differences. nothing so major it stopped me. i liked the idea of an exhaust manifold w/o a cat. brought my wideband o2 with me...left the air assist where it was. all went together and she was alive once again. a week later a fuel injector quit. i thought no biggie, i've got 4 of them sitting on this engine stand. HAH...another cali suprise. so i went to my local pull-a-part and harvested 4 federal injectors...fortunately fed cars are plentiful. alive once again. now i've come to my exhaust work...which came down to a new downstream cat, flex pipe, plumbing in between, and the downstream o2...which i recycled...used the fed upstream sensor i had laying around. now that all the sensors are working, i come up with a pending 0420. not consistant enough to be a full code...unlike my 0440 code. my question is...any thoughts on how to fool the computer into thinking it's got both catalytic's? swapping into a federal computer seems like way too much work...a most common cause of the 0440 would be cool too...i've gotten used to the MIL...but would be cool to see the dash without it...

 

P0440 is a large evap leak , P0420 is a cat conveter below treshhold bank 1 .
california and federal O2s and A/F sensors are not exchangeable , the internal specs from each sensor are different , cali ecu and federal O2s is going to give you a P0420 code, still pending because is a two trip code ecm needs to see the problem twice to make it a current code . P0440 re inspect the vacum hose for the evap system a lot of DIY Mechanics swap the location of the hose by accident (intake maifold side )(see label on hood ), if this was my personal vehicle i will install all the old sensor from the original engine on to the used federal im engine . with the mix of im components the ecm is going to go crazy and will give you a bunch of false codes and the miles per galon are going to suck . you can fool the ecm to avoid the P0420 code ,you have to install a O2s simulator or a O2s extension se it on this ebay links Universal O2 Oxygen Sensor OBDII 02 CEL w/ instruction V1 | eBay

UNIVERSAL O2 SIM OXYGEN SENSOR SIMULATOR SPACER OBD2 02 | eBay

 

at the moment, as far as the 0420 code goes, i've done what you said. i've got the cali o2 in the federal exhaust manifold. I assume the reason i'm getting the code is just that, using the federal exhaust manifold, so i'm only running one catalytic converter, the downstream after the flex pipe. seeing as how the computer detects converter efficiency based on voltages sent from the downstream cat, couldn't i (theoretically) put a resistor in the downstream o2 circuit to drop voltage to make it appear leaner after the catalytic converter?

 

and actually, milage isn't bad...not as good as it was in her younger years though...i get about 29mpg combined...i remember milage in the mid 30's...but i'm attributing that to suspension issue's i'm slowlly trying to iron out

 

right having only one cat on cali im will give you a p0420 , because rear o2s is actin like a wave mode voltage fluctuate from .05v-1.0v more then 5 times with in 10 sec.the right resistor will do the trick (simulator is box whit the right resistor inside and fancy wires ) . if you install the wrong resistor it will lean the engine to much and then you will have a p0171 code wish is not god to have , if you don't have to fool the state for the im test . the extension on the o2s works best and is only a few bucks ,the ecm will see a normal sensor and because is away from the center of the pipe is not going to have air flowing true as much ,it will do the trick whit out leaning the engine .