I Need Help With A Po420 Code! Please!

[gibbster]

Problem with PO420
I have a 2000 Avalon and I keep getting the PO420 code. I have replaced my B1/S1, B1/S2, main cat and airmass flow sensor all in the last 8 months. The engine light keeps coming on and the code PO420. Toyota Dealership has checked it out twice and can not come up with the problem. Can anyone please help me out. I have had this car for 7 years and have never had any problems until now. I cant just keep replacing parts and not get rid of the code. Thanks in advanced for any help. The car is running great, the gas mileage is great just as good as it was 7 years ago and I have had no problems with the car until now.

[kegunder]

I see that you've seen the recent thread on this.

http://www.toyotanation.com/forum/t237995.html

I just have my original cure (i.e. ignore the problem) and wild speculation.

Maybe the engine has sludge. I'm not sure why this would cause the problem, but if the engine is not breathing right, who knows what may happen. There is a product called auto-rx which may help.

I've also read that some people have installed a "fake O2 sensor" in these cars. That may help, but may also cause other issues. You'll need to search this forum (or the other Avalon forums) to find out about the fake O2 sensor.

[kegunder]

I also ran into this discussion on another forum. It seems that many makes have been seeing these issues.

http://www.bobistheoilguy.com/forums...45#Post1110845

[csaxon]

gibbster, your cat has an 8 yr 80000 mile warranty. Toyota is flexible if you contact them and ask for a good will variance,I.E. the 80000 mile cat quit at 85000 miles can you cover the cost or some of the cost. They usually comply.
Also, there is a tsb that mentions re-flashing the PCM and or ECU to make it less sensitive to the 420 condition and defeats the PO420 unless the conditions actually warrant it.

I'm looking for the TSB# with no luck so far.