I recently pulled a P0420 off my 2006 GS300 AWD. I've already replaced the two sensors that are tied to the catalytic converter and that didn't solve the problem. While the check engine light went out for about 3-4 days it came back on. I've had the mechanic pull the code again and it was the same code. Looking at the screen you can clearly see that bank 1 O2 sensor is bouncing around pretty good. The code doesn't go into a pending mode either which is strange.

So, that all said I'm thinking of replacing the cat altogether. I can smell it when I really get on the engine although the mechanic ran a bore cam and said that it looked clean. The prices for these things are all over the map. From $200-1000+. I obviously want the cheaper one. However, the cheapest ones are not California nor CARB compliant.

My question is if I choose to use a non-compliant cat will I still see the same code pop back up? I don't live in NJ or CA so I'm not worried about meeting emissions.

 

CARB compliant are for states that require it, you can buy a non CARB one and be good. If the code comes back it wont be becuase you bought a NON CARB Cat its becasue of something else like a air leak in the system or something else.

 

Thanks for the heads up. So an air leak can also create the same code? Would I be able to hear the air leak if I were trying to pinpoint it?

 

AWD exhausts are known to leak at the mid pipes (near the o2 sensors) from both pipes under the heat shields. The cause is from the heat shields themselves they collect water and theres a fiberglass matting inside that gets wet and that moisture surrounds the exhaust pipe and slowly the pipes rust away.

If you own an AWD to prevent this, what I did was I removed my heat shields. If you crawl under the car with a 10mm socket you can unbolt them unless if they were rusted out like mine were. I had to cut them out, the metal is very thin and cuts easy.

 

So did you pull the same code as I did on mine when you had this problem?