2020 2500HD Denali Power Loss

tima0101 · February 17, 2020

I recently purchased a 2020 Duramax 2500 Denali. Noticed a couple times driving on highway without really any load on the truck that it was either slipping (transmission) or cutting power. Super jerky and the RPMs kept going up and down. Had to baby the throttle for a while to keep it moving down the road. No codes or dash warnings. That's happened 5-10 times in the first 6,000 miles of driving. Yesterday I was pulling a trailer (7,000LB) and the truck kept cutting out power at highway speeds. Just no response to the throttle, truck jerks, then power comes back. Finally the dash warned me "engine power is reduced" then a second warning came on that said "service emission system." DEF is full. It was between 0-10 degrees F outside. Check engine light came on but this morning it was off. Was able to drive 100 miles home. Dealer is telling me it's bad diesel but seeing as this has happened consistently through 6,000 miles of driving and I buy fuel from different vendors, I don't buy it's a fuel issue. Anybody else had this issue? Also worth noting this issue has never happened until more than 30 minutes into my drive.

Thanks for any help.

Beach0433 · February 17, 2020

Did they pull the codes out of it? Doesn’t matter that the check engine light went off. The code is stored in the history.

tima0101 · February 17, 2020

I asked Onstar to pull codes and send me a report. Their report didn't show any codes. Dealer can't look at truck for a month.

redwngr · February 17, 2020

At 0 to 10F I'd be suspicious of fuel gelling.

Source of fuel? Is the source likely to have had 'winter blend'?

Of course that wouldn't explain the other times there have been problems.

What % is remaining on the fuel filter?

Symptoms certainly sound like fuel flow restriction.

Before the fuel filter update in about 2010, standard recommendation to new owners was to carry a fuel filter and know how to change it on the side of the road (used to be able to do that from above).

Classic symptom of needing to change was pulling out to pass -- truck accelerating fine -- then falls on it's face as the fuel flow cannot be maintained.

Maybe there is something going on with the filter and/or the fuel pump at the tank.

Xzy · February 20, 2020

My truck is doing the surging thing, but not at highway speeds. It also feels like your on a rumble strip when it shifts gears. It has been doing this since 2k miles, and got real bad the other day. Im at 8k miles and took it back to the dealer for the 3rd time and told them to keep it until they figure it out. I called them a day later and the transmission is full of radiator fluid. They have no idea how to fix it right now but obviously my transmission is trashed.