2003 Silverado ( 6 cyl )
185K Miles
Codes 420 and 430

Recent work was the Evap valve at fuel tank replaced with new model (I was against new model) due to manufacturer not making the OEM any more. All new wires, plugs, cap, rotor, and a few water hoses.

Dealership tells me I have to upgrade the system because the OEM collected water and the new one doesn't. However, it wasn't just the sensor, it had a new hose attachment as well. Plug and play kinda deal. No problem. Did that and codes went away.

Since the computer was cleared the new codes that show up within about 30 miles of the ECM cycling both Bank 1 and 2 Catalyst systems are operating below threshold. Now, I am very mechanically inclined (at least I like to think so, lol) but I am beginning to think that with the upgrade of that new EVAP Valve, I will need to upgrade the Cats to run with it. I would like for someone to tell me that this conspiracy theory is wrong, and that it's something so simple that I don't need to throw any more parts at this. Don't really want to cut out her Cats when there is nothing really wrong with them. They are operating within specs.

Any ideas? I can provide pictures of the new EVAP Valve if necessary.

Best regards,

IsleGirl

 

Your recent replacement of the EVAP valve really has nothing to do with you poping P420 and P430.

I would guess it was merely a coincidence,and with 185K miles on the clock,not that unusual.

It is time to replace the Cats,not really that expensive,and your truck will run like a dream.It is a simple remove and replace bolt on procedure.

You didn't say it was running rough or stumbling which could be a O2 sensor with P420 and P430,but not always.

P420 and P430 together almost always mean the Cats are toast.
So who told you the Cats were operating within specs?

 

Thank you, 67Motorcat. I will check into replacing the Cats. As far as being told the Cats were operating within specs should not have ever been typed. I was furious at the moment that I needed too ask and sounded like a conspiracy theorist in my original post. That female pride of mine () is hard to deal with sometimes so please disregard that inaccuracy.

I am going to replace the Cats and will get with you the results of this project. Please pardon the late response.

Best regards,

Islegirl

 

Two completely different systems. As stated above replace the cats and your codes will be gone.