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CEL with Service Emissions System message on 6.6L GAS

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   I have a 2021 GMC Sierra 2500HD with the 6.6L gas engine and roughly 8K miles. At the end of last week I was on the highway and my CEL came on and I received a message that said "Service Emissions System within 7 days" or something to that effect. I called my dealer right away and they booked me out a little over 2 weeks and now the CEL and message went away. The truck never ran any differently. Everything I find on the web refers to the Duramax and a similar message. I'm still going to have it checked out but 1) any one else have this message on the gas engine and what was the cause, 2) should I be alarmed that I can't get it in sooner, I only put about 100 miles a week and 3) should I be relieved, alarmed or neither that the code went away after running it for a few days (maybe 50-60 miles). Thanks!

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1). Not yet, truck only has 1,300 miles.

2 & 3) . Since the CEL is no longer illuminated, I'd be relieved, but would still keep the dealer appointment.  Do you still have OnStar activated?  If so, they may be able to tell you what the code is, and provide input on what you should do.

The Owner's Manual speaks to this in a generic fashion.  The '22 Owner's manual is page 117 & 118.  Your manual may be different pages.  If you have downloaded the pdf version, you can do a ctrl+F to bring up the search box, and then type the word emission to help you find the pages that cover the very generic explanation.

Hope this helps. :cheers:

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