Code PO422

[chwilliams]

On a road trip my '24 Chevy 2500 L5P lit the dreaded check engine light. The MyChevrolet app said it was related to the "emissions system." When I took it to a dealer, the service rep said "A '24 diesel? Of course it's an emissions problem!" quoting me needing to keep the truck for at least 4 business days because they'd be needing a part but they'd have to look at it first to figure out which one. After an hour in the waiting room he informs me the code was PO422, which they'd never seen before, and that GM said was innocuous, to clear the code, and ship it. Anyone else seen something like this?

 

Rig has about 3k on the clock so far, with the road trip accounting for 1600 of them. It's towed some already, but the majority of the miles have been unloaded interstate, driving with a lead foot. Got 21.5 mpg per 50 miles regularly on the trip, with a high of 25.7. Average with mountain and city driving was 18.1. Ran mostly Chevron fuel with Hot Shot's Secret EDT.

 

The only other issue I've seen is twice the front left turn signal died, but resurrected itself upon restart, both occurrences before the road trip.

[madweazl]

I got a P2534 and C0616 one morning but they went out after an ignition cycle (maybe 2; I can't recall) and haven't come back. Think we had right around 1k on the odometer at the time and now were sitting at 4k. Not much info was available on the codes but P2534 stated "ignition switch run/start position low" and if I remember correctly, it had failed to remote start that morning. I've never found info on the other code. I was planning on having them check it during the first oil change.

And I've never gotten close to your mileage numbers but most of our non-towing mileage is city driving. About 25-30% of the miles have been towing our 35' 5th wheel and I've managed 11mpg if I kept it at 65mph. At 72mph (where I typically end up), I get about 9.5mpg. 

After looking at what I've posted, none is useful to you LOL. Oh well, guess I wanted to share my CEL story. 

[chwilliams]

The mileage appears to be highly dependent on conditions, even a slight grade on the interstate, or a head or tail wind, will move it measurably up or down. IIRC that crazy number came from Hwy 99 in central California.