I had the check engine light come on in my 2000 Toyota Avalon XLS (85000 miles) and I took the car to autozone and my local mechanice both of whom diagnosed the error code as P0420 - Catalyst System Efficiency Below Threshold ( Bank # 1). My mechanic said this problem was common on avalons and attributed the reason to the catalytic converter failure. He said it would cost me $ 630 /- for parts + $ 100 /- for labour to replace. Which In my opinion is too high. Has anyone faced a similar issue before ? There is no effect on the performance or MPG of the car. What could've gone wrong and how much will it cost me to fix ? Is it really the Cat conv or the O2 sensor ? Incase its the cat, can I buy one from junkyard ? Also will it have any effect on the car in the long run ( besides failing the DMV Inspection) if I continue to drive without addressing this issue.

You didn't state millage, but I don't think the cat is bad. More likely it's the O2 sensors. They need to be replaced about every 100k.

OEM Cats are around $700. After market ones are total junk and don't last. And it's against the law to take emissions parts from a junk yard,

Thanks LotOmiles for your reply....I had stated in my post that my car has done 85000 miles ! do you have the part numbers alongwith the price for the cats for avalon ( or know where I could get my hands on this data ?) ..it seems there are multiple cats in the car and their prices vary greatly.

~A

Yes you did. I am just blind. (IMG:style_emoticons/default/grin.gif)

I don't have the part numbers of price, but you can call your dealer to find out.

O2 sensors are about $120.
http://catalog.eautopartscatalog.com/palac...t=Oxygen+Sensor

I also have a2000 toyota avalon and i had the same problem replace your bank 1 02 sensor located on your ehaust manifold nex to firewall disconect battery for 10 minutes to reset if you still ha problem let me know

surprisingly the CEL has disppeared on its own....i took it to the mechanic and the code was still being shown as P0420...so he erased it and told me to drive the car to see if its comes back again...its been more than a week since and 200 miles and the light hasn't come on !!!!

Just to mention, i changed the gas station and filled up premium exxon fuel this time...will also be adding fuel injector cleaner the next time I tank up just to prevent such problems in future.

So long till then, just keeping my fingers crossed and hoping for the best !!

~A