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Discussion Starter #1 (Edited)
Well just got back from our Thanksgiving trip to Calif. (4995 total miles) Truck did real well with no comfort issues, MPG averages were a low of 22 and a high of 30. Speeds ranged from 65 to 95 MPH (all interstate). Did have one issue though, had a DIC prompt saying "DEF quality poor" and had it go into "limp" mode at 65mph and then down to 55mph (man did I piss off some truck drivers on I-70, Sorry to all of you!) until I could locate a Chevy dealer in Moab Utah named Crump-Reese Chev/Ford/Buick/Jeep (a BIG shout out to Jordan and the guy's!!). They got me in right a way and plugged-in and ran diagnostics and tests for 1 1/2 hrs. and could not find an issue or duplicate the problem, cleared out a couple of codes and sent us on our way with no further issues so time will tell. If any of you ever get the above mentioned prompt, find a dealer right a way because if the vehicle goes into limp mode it will reduce speed all the way down to 5mph. I think that if the conditions are lined up just right and you are on the Interstate some where and your speed is reduced just to keep pollutants out of the air, it can put you and others in a dangerous situation.
 

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Discussion Starter #3
I had exactly same problem with my truck. Run diagnostics and install latest updates. No problem found. Still a PITA.
Well these guys ran two test that GM recommended and could not duplicate the problem and like I mentioned, they had it for an hour and a half, didn't say they re-flashed the ECM or anything. I even poured 2 more gallons of blueDEF into the tank like the manual says before I got to the dealer, with no results. So I am at a loss. All I know is that I didn't have anymore issues the rest of the trip home and I was cruising at about 85mph until I hit Iowa. All I can think of is that the system had a bubble in it just enough to throw a code and then it would not clear/reset itself and the hunt for a dealer was on. Still good at this time. MADMAC:)
 

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Hello fellow Baby Duramaxers,

For Thanksgivings, the Colorado went on a 250 mile trip (500 mile round trip). According to the truck computer it did 31.5 average MPG one way, but that turned out to be 2 MPG too optimistic. I say that because it conflicts by that tad when figuring the MPG the old fashion way. The old fashion way goes as follows: start the trip with a visit to gas station to fill diesel tank up completely. Next, reset the chosen trip odometer and off you go. When at or near your destination stop and fill the gas tank up completly. Now divide the trip miles displayed on the correct trip odometer by the gallons of diesel you just pumped into the tank. This number is the true MPG...end of story. On this 2017 Colorado 2.8L crew cabin it yielded 29.3 MPG! Not bad, and we're happy with the result. On a further note, calculated the old fashion way, the 2018 Honda Ridgeline did 25.2 MPG on this same exact trip (same pt of orgin and destination) one way. This vehicles' MPG computer was also too optimistic, but by only 1MPG.

Very happy with the 2.8L Colorado so far (2k odo miles). No issues and best MPG of any modern pick up truck in North America. And we are proud that the emissions is cleaner across the board to even the 2018 Ridgline! I know this because it has to be, since gas engines don't even have an exaust particulate filter!

[email protected] yeah Duramax!!
 
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