Strange 3.0 Duramax engine noise now...fixed???

Rubyralph · November 4, 2020

Strange story but I'll break it down and make it as simple as I can...

Bought my new 2020 Duramax back in April, during the test drive at the dealership I noticed a CEL and pointed it out to my salesman. The Dealership cleared the CEL before delivery (55 miles on the odometer) and the repair order said they replaced the "Emission Reduction Fluid Tank" because the reductant heater 3 current was high scan code: P221F.

Fast forward to 2400 miles, After mixed driving and towing maybe 200 miles of towing total I noticed two things about my 3.0 Duramax, first the engine always made a muffled noise when coasting below highway speed, sounded like a mini Jake brake.

Secondly I hadn't seen any drop of DEF on the dash screen until after 2400 to 2985 miles and then just one bar.

So today I got my free LOF and tire rotation and wouldn't you know on my drive to the dealership I got a CEL Emission warning "169 miles to reduced 65 MPH speed"

The Techs repair order states that codes "2985 P21DD 00 P221E were set in ECM, the fix was to install a recall "N202300791 Diesel Exhaust Fluid Inactive Recall" per recall reprogrammed exhaust fluid module.

Now maybe it was the recall or something else the Tech found but now my truck's Duramax engine is NOT making the muffled noise when coasting below highway speed and I think I actually can hear a very faint turbo wine when accelerating! I hope ever thing is now fixed correctly?

Has anyone with the new 3.0 Duramax heard of this happening? Thanks

Crazypontiac03 · November 4, 2020

I haven’t heard anything but now I’ll be listening for it. Mine currently has little over 600 miles on it. I’m not sure I’ve even used any DEF yet.

One thing I wish GM would change is adding a “Regen in process” to the instrumentation display too..

jnissen · November 4, 2020

I had mine in to dealer a week ago to enable the fog light kit. They mentioned a recall for the DEF tank. Think it was just a program update. When I went in my DEF showed one bar low and when I left it showed a half tank. I went home and added 2.5 gallons of DEF and it now shows full.

There were reports of the DEF fluid level not being accurate. They may have added some averaging to the sensor reading so it’s a bit more accurate. At least that’s what I suspected.

Yours may have gone into limp mode for low DEF. after its reporting more accurate DEF so running more like it should? At least my best guess.

Btw - I had no noticeable change in noise or drive characteristics.

redwngr · November 6, 2020

On 11/3/2020 at 8:55 PM, Crazypontiac03 said:

One thing I wish GM would change is adding a “Regen in process” to the instrumentation display too..

No likely to happen. It's been a duramax complaint as long as they've had regeneration -- so since 2007...

GM's intent is that it not impact operation of the vehicle, so no need to notify when it happens.

yousaveone · November 6, 2020

I was told the DEF recall was for trucks that either A used NONE, or B trucks like mine that used a TON of def. Either way after the def recall mine has stabilized and uses way less been consistent for 15K. Question is what affect of using none or too much has on the exhaust system.

Robdeuce · June 30, 2021

I have same noise on 2021 3 litre , noticeable on slow down , was your problem fixed?

Rubyralph · June 30, 2021

6k miles and still have the noise, normal for my truck, check my other posts about my DEF system. Dealership replaced the entire DEF tank, pump, heater and wiring harness, seems to work now. Towed 4K lbs. 300 miles last Sunday and the truck towed great and even downshifted in tow/haul with cruise control on down a long grade at 50 MPH! Very happy with the truck now if I can stay out of the dealership!!

!

aaron moore · August 13, 2021

I have a 2020 with 28,000 kms.
I had my def level drop out very quickly on me, went from over half tank on the indicator to the "crawl mode" warning while driving through town.. And now a few weeks later my engine is making the jake brake noise you are describing above.. What was done to your truck to fix all that?