https://www.reddit.com/r/gmcsierra/comments/1aqhfvu/emissions_issue_on_brand_new_2024_sierra_2500hd/
Emissions Issue on Brand New 2024 Sierra 2500HD : r/gmcsierra
Feb 14, 2024 ... Comments Section ... P0422 is saying Catalyst Number 2 is inefficient. The bulletin states to clear it, and if it comes back, then diagnose it.