P0420 and P0430 at same time
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From: Thousand Oaks Ca
P0420 and P0430 at same time
I have a 09 Z06 with a Magnuson Supercharger. 53k miles. The car runs great. But, while driving and coming to a stop the check engine light will come on with P0420 and P0430 at the same time. I had my code scanner plugged in to verify. This usually happens after driving about 25 miles. I already took air filter out and cleaned it, cleaned maf and cleaned throttle body. New rear 02 sensors a few months ago.
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From: Cape Coral, Florida
Has any recent exhaust work been done to the car since those DTC’s have appeared ??…the things you have done are not related to those DTC’s (air filter, MAF and TB)…I’d make sure that your 2 downstream O2 sensors are tight and when looking at your scan tool are the rear O2’s steady after the engine has been warmed up…they normally sit around 700-800mv’s…upstream O2 oscillate between 200-800mv’s…can be a premature catalytic converter failure but you want to make sure sure you check everything else before condemning them…things like misfires that have gone undiagnosed, fuel trim issues, excessive blow by, and some fuel additives can contribute to this…I would get it professionally diagnosed (not a general repair shop or dealership) before replacing the cats since the ones you should be installing are very expensive…there is a recall on the cats for your 09 but are limited to the LS3…there is also a TSB pertaining to premature cat failures and involves checking the coil pack ground wires…I doubt this is your issue…a cat failure is an “effect” and NOT a “cause”…you need to find WHY it failed if so.
Last edited by C5 Diag; Mar 5, 2025 at 11:06 AM.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,626
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From: Cape Coral, Florida
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,626
Likes: 4,070
From: Cape Coral, Florida
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,626
Likes: 4,070
From: Cape Coral, Florida
Even Corvette “Specialty” shops are not best at diagnosing…good installing your supercharger but possibly bad when it comes to diagnosing but hopefully you can get it fixed…tell them to do an “oxygen storage” or “propane enrichment” test…that will help diagnose it…if they’ve never heard about it you took it to the wrong shop…a shop that is familiar with this test knows how to diagnose cars…they don’t guess !!
Last edited by C5 Diag; Mar 5, 2025 at 11:54 AM.
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Thread Starter
Pro
Joined: Aug 2011
Posts: 522
Likes: 45
From: Thousand Oaks Ca
Even Corvette “Specialty” shops are not best at diagnosing…good installing your supercharger but possibly bad when it comes to diagnosing but hopefully you can get it fixed…tell them to do an “oxygen storage” or “propane enrichment” test…that will help diagnose it…if they’ve never heard about it you took it to the wrong shop…a shop that is familiar with this test knows how to diagnose cars…they don’t guess !!
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,626
Likes: 4,070
From: Cape Coral, Florida
OK, well C&S Corvettes down here in Sarasota Florida is a well respected shop and they don’t do “involved” diagnostics or electrical work…they will turn down the work or send the car elsewhere…and let us know if they’ve heard of that test…working on “everything” is not the same as diagnostics…just letting you know my friend.