2019 2500 6.6 Duramax High Idle

Brad Carruthers · September 25, 2020

I am new to owning a diesel. My 2500 usually idles at 600 rpm’s. It has been running great but for the last few months it will for no reason start idling at 800 rpm’s. Has anyone else experienced this or know why it does it?

Colossus · September 25, 2020

The idle will go up to about that when your truck is trying to do a Diesel Particulate Filter (DPF) regeneration cycle. Get it out on the highway and drive it for 20 miles or so at highway speeds and the regen will complete and RPMs drop back to 600. Read up more about it in your engine section of your owners manual. Best to do regens at highway speeds. They run automatically and you can't control when it goes into or out of regen, gotta let it do its thing. It will only regen over certain speeds (45+ I believe)

Brad Carruthers · September 26, 2020

Thank you Sir!!

Colossus · September 26, 2020

My pleasure. Enjoy your Duramax!

redwngr · September 28, 2020

ECM can/does raise idle for several reasons:

From Duramax supplement:

Under certain conditions the engine idle speed can vary or be elevated.
Change in idle speed is normal and does not indicate a problem. Normal
conditions that can raise idle speed are low voltage, DPF regeneration,
air conditioning compressor loads, and engine warmup. These speeds
can range from approximately 600 to 1000 rpm.