Something upstream of the cat is causing the code.  Replace the gas sensor (whatever that is).  Is it burning oil?

Hi Scotty,

I just moved to Spring, TX from Europe so I am not familiar with the US car repair process. I have a 2004 Toyota Camry LE V6 3.0L with 140k miles. Check engine light is on due to code P0420 Bank 1. Bank 1 converter needs to be replaced and Bank 2 is also showing less than ideal live data (no code yet). However all car shops that I have visited have quoted me extremely high prices. $4k for replacing all converters or $2k for replacing only the one that is giving the code. They also dont want to use after market parts (I assume they wouldnt make much money on those). What do I do? I dont want to spend that much on an old car using original parts. Do you know a good mechanic in Houston area? Does using after market parts make sense in old cars with short remaining life left in them?

Thank you!

Tobias

I have a 2000 Toyota celica gt with code 420 . I replaced all fuel injectors,with the Toyota injectors,code went away for 4 months ,and recently came back on,car runs normal ,no loss off power or smoke out of the tail pipe, only thing I am not getting good gas miles . Thank you andrew

I have a 2008 jeep jk with 135000 miles and it's throwing a p0420 bank 1. I've installed new o2 sensors to make sure they were ok but the code came back. Before replacing the catalytic convertors do you suggest ruling it anything else?

P0420 , P0430

2004 Dodge Ram 1500

459333 mi.

5.7 hemi magnum,  Automatic

Had the O2 censors replaced and shortly after that, received both codes.

Cleared the codes and they keep returning. 

Using Autel meter. 

When reading both sensors on both banks

O2B1S1, .055-.840

O2B1S2  .075-.800

O2B2S1, .055-.820

O2B2S2, .135-.820

O2 censors were changed when shorty headers were installed when changing exhaust gaskets. 

It's smog time...

I've had people recommend swapping the censors, but sense it involves bit banks, that doesn't make sense to me. 

Makes more sense to me that Tybee new censors are poor quality but would rather do more diagnostics rather than just swapping out parts. 

Recommendations as far as testing? 

Hi Scotty,

I have a 2006 Toyota Highlander, automatic, with 185k miles and I am the original owner.

The check engine light came on and I used my scan tool, I received the OBDII codes P0430: catalyst efficiency below threshold bank 2.

The scan tool suggests replacing the catalytic converter.

What do you suggest?

or cut cat off the car? less problem to deal with