P0420 Code Issue On 2001 Corolla

Did you reset it each time. you can do so by disconnecting the negtive battery termal for 10-15min or the ecu fuse for 5-10min. And check again. But I would think that it is the 2nd o2 sensor though. Not really sure though

I remember seeing on one of the corolla forums that pulling the ecu fuse for just 1 minute will do the trick. Does anyone know if this is correct or not?

Kul did you install a oem o2 and oem cat coverter or did you buy universal? If not oem people do have problems with universals. I believe I have seen that you may have to reset the computer more than once after installing o2's and a coverter can anyone confirm this is so? If you went with oem and indeed it is confirmed that the cel can come on a couple times after o2 and coverter installation then I'd reset the ecu and see how that goes. If the cel comes on again then I'd say it'd be time to consider installing a rear oem o2. If so the cheapest price I could find for it #2344625 is $101 from oxygensensor.com. I just bought one yesterday.

Btw if you bought a universal front o2 then I'd consider getting the oem o2 #2344205. I bought the last one off ebay yesterday for $74 total but you can check and maybe there will be more if you need it. Next best price I could find on it yesterday was $86 at rockauto.com.

Hi

I did change the secondary O2 sensor, and reset the computer and the code came back again

I have oem O2 sensors and the catalytic converter is by Eastern Catalytic Converter , i purchased it from carpartswholesale.com

i the O2 sensor are by bosch,

so what do i do next? any suggestions

I believe I remember seeing that you may have to reset the ecu again a second time because the cel will pop up after the install the o2's. Did you install the o2 with the engine cold or after it was warmed up? If while cold then that can supposedly cause problems. Other than that I would have no idea what to suggest other than a leaking gasket maybe.

Hi

I did install the O2 sensor when engine was warm,

Is there a way to check for exhaust manifold for leaks, can i do it home

My guess would be to use something that smokes like cigs or incense, or spray soap water to check for bubbles. Maybe a tissue on a cold exhaust once the engine is started so it wouldnt catch fire when touching it?