P0430 at 5,000 miles?

Tnsilverado · December 21, 2023

I have a 2018 Silverado 1500 with the 5.3. My truck has 4,900 miles on it. I just picked it up a few days ago. The engine light came on and shows a P0430 code. Catalyst inefficiency bank 2. The dealer told me it’s cause the truck had sat most of its life with the majority of the trips being short. They told me to run fresh fuel in it and run it hard and that would work. Well that’s what I’ve done the code keeps coming back. I find it hard to believe the truck has a bad cat at less than 5,000 miles. It runs perfectly fine just has the code. Here’s what’s weird hooked up my scanner and my mass air flow is in spec bank two oxygen sensors look good front and rear as does bank one rear. However bank one sensor one the voltage is all over the place could be .08, .881 or anything in between at any given moment. It never settles. Would this not cause a code for bank one instead of bank two? The truck is still under a 10 year 100,000 warranty, so I can get it repaired but it’ll be a few weeks before they can get me in. I just wanted to see if anyone had any insight as to what may be causing this issue. Bad cat, bad oxygen sensor? Or is just from sitting too long? Any help would be appreciated. Thanks.

CamGTP · December 21, 2023

Upstream o2 sensors are suppose to switch lean and rich of stoich. With that being roughly 450mv using an o2 sensor. They are designed to bounce up and down as the fueling changes and will make corrections on the fly.

If your bank 2 sensor 2 o2 sensor is not settling in around a specific range and is kind of following the upstream o2 sensor, that could be why it's tossing the code. You could also try spacing the o2 sensor out of the exhaust stream to stop the code from coming back.

rav3 · December 21, 2023

My '17 Silverado with 5.3 v8 threw the P0420 code two weeks after I bought it as a Certified Used truck @ 31k miles. This code is the same as yours except bank 1. The dealer replaced the "Y" Pipe that has all 3 cats under warranty. It was my understanding that this was a known issue, as the dealer told me they were on back order.

ADDED: For what it's worth, I had just done a CRC GDI cleaning 300 miles before this. You can always run some Cat Cleaner through it.

Edited December 21, 2023 by rav3