3.0 Duramax exhaust smell in cab

IcemanNY · January 5, 2021

I’ve got a ‘21 3.0 with 1700 miles on it. I had it to the dealership for a strong exhaust smell in the cab that I only seem to get when auto starting every morning. Also at the same time it smells heavily of diesel fuel around the gas tank area of the bed. No leaks were found, but the dealership didn’t it look at the truck when it was cold, only at operating temp. Anyone else experiencing this?

davidr83 · January 5, 2021

Exhaust smell will continue for a while till you put more miles on it. This is common for the 3.0L. Mine smelled bad at first and I thought the same. after around 5-6k miles the smell was pretty much gone, or I just didn't notice it anymore but it's definitely gone now at 21k miles. Can't speak on the diesel smell, maybe someone spilled fuel at some point during assembly or before you took delivery. Hopefully the flappers in the fuel neck are closing properly after refueling.

IcemanNY · January 6, 2021

Alright, thanks for the info. I’ll give it some more time and see what happens. Besides these two issues, it’s a great truck.

Kchampagne · January 6, 2021

This is a known problem. I had mine in for the exact same problem with exhaust smell in the cab. Only when cold a few seconds after startup. The dealer did a leak test on the exhaust and diagnosed it as a bad def injector and clamp. It took a month to get the parts on backorder. Just had mine finally fixed last Friday. I would press the dealer on this problem. It is not good to be breathing exhaust and carbon monoxide in the cab. Now, getting a burning smell around the time the engine does a def regeneration is normal, especially for the first few thousand miles. However, the exhaust smell at cold startup is definitely not the def regeneration.

davidr83 · January 6, 2021

8 hours ago, Kchampagne said:

This is a known problem. I had mine in for the exact same problem with exhaust smell in the cab. Only when cold a few seconds after startup. The dealer did a leak test on the exhaust and diagnosed it as a bad def injector and clamp. It took a month to get the parts on backorder. Just had mine finally fixed last Friday. I would press the dealer on this problem. It is not good to be breathing exhaust and carbon monoxide in the cab. Now, getting a burning smell around the time the engine does a def regeneration is normal, especially for the first few thousand miles. However, the exhaust smell at cold startup is definitely not the def regeneration.

This is a good point, @IcemanNY@ are you actually smelling exhaust or just a burning smell? I assumed you were referring to the burning smell that some people refer to as exhaust when these trucks are new.

Edited January 6, 2021 by dram1983361

IcemanNY · January 6, 2021

No, it’s definitely exhaust fumes, only at cold start up. I’ll get it back to the dealer and mention that others have seen it.

Kchampagne · January 6, 2021

33 minutes ago, IcemanNY said:

I’ll get it back to the dealer and mention that others have seen it.

I dropped my truck off at the dealer the evening before service so the techs were able to immediately replicate the exhaust smell at cold startup the next morning.

Edited January 6, 2021 by Kchampagne

PtownVdub · January 8, 2021

My 2020 Sierra 1500 SLT with 2700 miles is doing exactly the same thing and has been doing it as long as I have had the truck. Cold start in the morning results in diesel exhaust smell in the cab. I have also noticed that occasionally I will smell diesel exhaust in the cab sitting at a light before the truck is completely warmed up.

@Kchampagne would you be able to take a picture of your work order that describes what your dealer did to diagnose and fix the issue? I want to be armed with as much information as possible when I drop my truck off at the dealer. Thank you!

Kchampagne · January 8, 2021

49 minutes ago, PtownVdub said:

My 2020 Sierra 1500 SLT with 2700 miles is doing exactly the same thing and has been doing it as long as I have had the truck. Cold start in the morning results in diesel exhaust smell in the cab. I have also noticed that occasionally I will smell diesel exhaust in the cab sitting at a light before the truck is completely warmed up.

@Kchampagne would you be able to take a picture of your work order that describes what your dealer did to diagnose and fix the issue? I want to be armed with as much information as possible when I drop my truck off at the dealer. Thank you!

Here you go.

DemonWorks · January 8, 2021

I have the same, only with cold morning remote start.

Pin High · January 8, 2021

@Kchampagne Thank you for the repair order info. I have a 2021 GMC 1500 with 600 miles. And, I just called my dealership last week about the diesel exhaust smell in the cab during cold startups.

Kchampagne · January 8, 2021

The part numbers for the def injector and clamp are listed on the invoice. The dealer said the main culprit is the clamp, but replaced both. Just FYI, I did not have the exhaust smell (for 9,000 miles) until the dealer replaced a bad def injector. I had to bring it back a second time and they replaced the injector and clamp again. This took over 3 months. The def injector and clamps are in short supply nationwide. Fingers crossed, it seems to be gone.

redwngr · January 9, 2021

Seems that some trucks with the clamp issue also develop a fault code.

In any case, I believe these pics are the clamp and sensor in question.

There is a smoke test they can do to determine if that is the source of the leak.

https://gm-techlink.com/?p=1378

Particulate Matter Sensor Protection Tube Performance Diagnostic Setting False DTC

October 13, 2020

The particulate matter sensor protection tube performance diagnostic may set a false DTC P1488 (Particulate Matter Sensor Temperature Circuit High Voltage) on some 2020 Silverado and Sierra trucks equipped with the 3.0L Duramax diesel engine (RPO LM2). The Check Engine MIL also may be illuminated.

If the vehicle has DTC P1488 set, check if the particulate matter sensor is loose in the exhaust pipe. If the particulate matter sensor is loose, follow the diagnostics in the appropropriate Service Information.

If the particulate matter sensor is properly torqued and DTC P1488 is set, test the exhaust for leaks using the GE-52250 Power Smoke Diagnostic Leak Detector. Since the sealing bladder cannot be installed in the tailpipe upstream of the exhaust cooler, it’s recommended to use duct tape to seal the cooler.

Repair any leaks as needed and replace the particulate matter sensor.

If the joint shown is leaking (Fig. 23), the clamp may have bottomed out before sufficient clamp load was applied to the joint. (Fig. 24) The clamp should be replaced if this condition exists.

Fig. 23

Fig. 24

Refer to #PIP5748A for additional information.

IcemanNY · January 10, 2021

Thanks for posting that repair order. My truck goes in Monday overnight for diagnosis. Hopefully this is the culprit.

OliverDennis52 · January 12, 2021

Let us know what they find. I also get the exhaust odor in the cabin on COLD starts, worse when in the garage and not so bad outside. I'm currently waiting on part for the radio, so when I take it back in I'm going to have them check this. I assumed it was "normal" being my first diesel since it's not super annoying and goes away once I start moving. I'm curious if most 3.0 owners don't get any exhaust odor at all on cold starts...