2004 Z71 Tahoe, P0420, P0430... Opinions?

[Grizzly]

I have a 2004 Tahoe Z71 5.3L. Babied it. Has 208k miles... I had a K&N Air filter in it for a year and would get a P0171 code whenever it needed cleaned, which I'd do and clean the air flow sensor with some carb cleaner and the check engine light would go away... Well I was at a intersection and it started to hiccup, wouldn't go past 10 MPH. I was told it was cause I lubricated my K&N filter to much so I replaced it with a generic filter and cleaned the sensor and it ran fine... Month later, same issue at a intersection. Wouldn't go passed 10 MPH. died completely, turned it back on and it threw a P0336 code with was indicating my Crankshaft position sensor needed replaced and thats why it kept dying... So I had a friends grandpa get under there and replace it with a new sensor. I drove it a good 30 miles and ran perfect. No issues. Next day on the freeway the engine light is back on but this time with a P0420 and a P0430 code and was told my catalytic converters are needed replaced... But I feel it has something to do with my sensor being replaced? Any opinions or ideas on what I can try to fix this engine code without replacing the converters? Any help is appreciated.

 

[MrSpicy]

Hi there I too am in a similar situation while trying to help my brother in law fix is 01 Denali. His is throwing p0420, p0430 as well. A problem upstream from the cats will lead to them being ruined or damaged or if you are lucky just the code being thrown.

I have read of someone changing their fuel filter and PCV valve and it went away probably not likely it will fix it but why not give it a shot not too expensive

. Also may want to take apart and clean the maf and the throttle body. It is probably dirty as hell from the K&N (personally I tell everyone its a bad idea but that's beside the point). Use some good tb cleaner and clean it up- at least that's what I'm gonna try with my brother in laws.

Also heard of replacing o2 sensors as well as covering one in red silicone to trick it into thinking its working.

But I fear that in both our cases the cats are probably In need of replacement. Especially since were both looking at 200k+ miles on the od

Let me know if you figure anything out. I'm in the same boat.

 

[WOOKIEE]

Unfortunately when you’re getting those codes it means the sensors are doing their jobs and telling the computer that the catalyst is not operating correctly. My guess is that you’re passing too much nox through the exhaust. The GM converter is very expensive but a great option are the Magnaflow systems. All mandrel bent pipes and perfect fitment.

 

[Bill-H]

A MAF sensor failing can show either Lean or Rich codes on the O2 sensors.

 

[afpj]

The OP mentioned cleaning air flow sensor with carb cleaner....hope that ain't true. need to use MAF cleaner for the MAF, nothing else. Carb cleaner not necessarily the same.