2009 ES350 with 180K has been randomly giving P0420 Catalyst Efficiency Below Threshold Bank 1 errors. I've cleared the codes and now I can't get 100 miles on it before it pops up again. We've got to have the emissions test done on it in a bout a week so I'm running out of time.

From what I've learned, Bank 1 is the firewall side (of course it is). How difficult is that to replace from underneath? I watched a youtube video of a guy saying it was fairly easy but wonder if you guys have any tips/tricks. I'm fairly capable of most repairs -I've replaced rear plugs/coil packs on this ES350 and my RX350 with help from this forum.

Is it worth it to replace the downstream o2 sensor for that rear bank first and see if that fixes it? I think I've learned that it would be the o2 sensor down by the y-pipe and not the one in the top of the converter itself, but it's been a little confusing.

 

I saw it done on my car and aside from a few rusty bolts, it looked like it was straight forward. My mechanic was done in 45 minutes or so.

P0420 usually means your cat is done. Your car has 180k miles so I'm not sure how much longer you plan on keeping the car...BUT, I would go OEM cat converter. You can probably get $50-$100 or so for your old CAT on ebay etc....

forgot to mention, he drove the car up a small ramp

https://www.autozone.com/p/hopkins-h...store_set=true

 

Just to confirm, you had the rear, firewall-side converter replaced by your mechanic in less than an hour?

 

Correct- I believe he had to move the flex pipe out of the way in order to remove the cat. Only thing that gave him issues were some rusty bolts.

He did the front one a year before and was done even quicker.

 

Thank you for the quick replies, good sir!

 

Have a torch ready in case you need to loosen any rusty bolts

oh yea, have a few bolts handy in case you cant reuse any of the old ones.

and bell lexus usually has the best prices online for OEM parts with free shipping

https://parts.belllexusnorthscottsda...715031161.html

 

Don't replace it. Just put spacers on both post-cat O2.

 

The spacer trick on the sensors is a great idea to save money on this car and get it past emissions inspection.

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The spacer worked great. $10 and 10 minutes to install it. You guys are awesome; thank you for the advice. @June1978, while I was under the car, I saw clear access to the rear converter bolts so with the right combination of socket extensions, it should be an easy repair if I have to go back under and replace it.

I used Dorman - HELP 18mm Gasket Seat Spark Plug Non Foulers 2 Pack 42009

 

I'm pretty sure O2 spacers aren't legal. If the tech spots them under your car you will fail the smog test. That said, techs rarely go under the car. They just plug into the ODB port and read the codes.