Hey all, I have two reoccurring codes, P0420 bank 1 and P0455. They come on after driving a while, then they will go off, and then come back on. My cats were previously bad, and I replaced them with low mileage ones I bought off the marketplace. This was good for a while then the code came up again, so I replaced the downstream 02 sensor. Code didn’t pop up again for a while, but now it’s back. Any chance it’s the upstream 02 sensor?

for the P0455 code, can it be related to the P0420 code? I bought a new vape canister vent, and will replace that to see if it fixes that code. Just waiting for the part to come in.

 

P0420 - Catalyst function bank 1.
P0455 - EVAP control leak

Normally P0455 is when people forget to put their gas cap on, or if the gas cap has a massive leak. Inspect the entire EVAP system for any broken components, major cracks or disconnected hoses, etc if the cap is a good OEM one. It's fairly protected under the vehicle but debris can still damage the hoses.

P0420, which downstream O2 sensor did you replace, this code is for bank 1 only. It can also be caused by exhaust leaks between the header and catalytic converter.

 

Hey Cleric, I replaced the bank 1 downstream 02 sensor. I really want to bring it in for a smoke test, but not sure it is the smartest thing to do with this Covid situation. For the P0455, I do get a slight gas smell on start up

 

As far as I can remember every car I've owned has had the gas smell on a cold start. From what I understand (which could be completely wrong) it's due to the rich mixture that is used during open loop operation until the upstream O2 sensors are up to temp and can give accurate readings for mixture purposes.