Dreaded P0420 code on my 2016 Malibu 2.5L

[SC Maintenance]

I'm not saying they may have gone 'bad', but they may be lazy, dirty and inaccurate.

Your correct. They get coated and their response time slows - especially if you’re burning any oil. The cat is likely shot , but it’s possible a now sensor will buy you an inspection. The rear sensors seem to take forever to throw their own code , unlike the A/F sensors in front.

 

[The Critic]

I'm not saying they may have gone 'bad', but they may be lazy, dirty and inaccurate.

I disagree. If the deterioration is meaningful, you will set a fault.

Also, if anything, new sensors will perform better and set the P0420 more quickly.

 

[Chris142]

Most of the time a 420 code is a cat that's not working up to snuff. I have seen it caused by another problem where the cat was unable to cope with another problem and threw a 420.

 

[panthermike]

Good luck hopefully easy fix. Ended up putting a spark plug fouler on our Corolla due to a persistent 420 code. 8000 miles later still holding up

 

[Doc8404]

If it runs as well as you say, $1600 might be worth it.

I just sunk $5k into my 2012 Altima I’ve owned since new. 140k miles.

Nothing wrong with her and buying a used car for $5k with unknown issues would be a gamble.

 

[D60]

I'm not saying they may have gone 'bad', but they may be lazy, dirty and inaccurate.

You should at least graph it then. That said, this is more effective for Luddites like me when there's a B2 to compare

 

[mattd]

You need to graph upstream and downstream 02 data. You’ll get your answer pretty quickly that way what the problem is

 

[zzyzzx]

Can you get away with using an O2 spacer in NY? I used one for years here and it worked great.

 

[JTK]

Can you get away with using an O2 spacer in NY? I used one for years here and it worked great.

You can. It might only be an issue if a shop was observant enough to discover emissions equipment had been tampered with.

Turns out I very much lucked out. The P0420 and P305F codes had stayed clear long enough for me to get the vehicle inspected today. I just picked it up. $38.24 total. $21 for the NYS inspection, $13.50 to jamb a plug in the right rear tire due to a nail / slow leak. Everything is A-OK for now and she lives on towards year 3.

That battery correlation code is a real pain with this gen. It pops up very intermittently after an auto stop/start cycle. It's got a new-ish (giant) under hood battery and has a small (motorcycle type) battery in the trunk due to the A/S/S. Problem with my trunk battery is a previous owner hacked the OEM one out and cobbled in small cables and an actual motorcycle battery. There's no way to shut off the A/S/S on this gen other than shift it manually, which is again a pain on this model as you actually have to +/- through the shifts. Those hood switch bypass harnesses set off the MIL on this particular model.

 

[chexxers]

dito on the cold with a 2011 fronty V-6