exhaust smell in cab '21 denali

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DuraYuk

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UPDATE AFTER LATEST FIX
Dealer received the parts and put them on the truck (Wednesday), they drove it and tested it a fair amount ~20 miles.
We picked up the truck, exhaust smell gone.

Drove it about 10 miles.

Still getting exhaust in cabin during cold startup.
And...
Check engine light, service emission system msg, reduced power msg on the dash.

Truck is back at dealer, they are assuming a failed weld on the valve but will test to verify.
Just as I expected. They are guessing and have now introduced some other issues because of tech incompetence. It 'was' something simple to begin with. Now you have to fix the initial problem and the host of other things they may have messed up doing what they did.

I'm sorry these incompetent service departments are souring the ownership experience for you guys. The turbo diag in the beginning never made any sense.

Keep us posted. The few smells that were reported were fixed with a cabin air filter replacement.
 
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steiny93

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UPDATE AFTER ANOTHER FIX
Exhaust smell at startup and lots of service emissions, check engine, reduced power messages on dash.

Dealer had truck for a day.
On the side of the turbo lives a sensor which failed. This is the brand new turbo which they just installed. They had a sensor available so they swapped just the sensor. Then they did another leak test and didn't see any leaks, swapped the cabin air filter and are having us try that. Driven it a couple times, it doesn't smell.
 

DuraYuk

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UPDATE AFTER ANOTHER FIX
Exhaust smell at startup and lots of service emissions, check engine, reduced power messages on dash.

Dealer had truck for a day.
On the side of the turbo lives a sensor which failed. This is the brand new turbo which they just installed. They had a sensor available so they swapped just the sensor. Then they did another leak test and didn't see any leaks, swapped the cabin air filter and are having us try that. Driven it a couple times, it doesn't smell.
At least they are quick about it. They are gonna get charged back for that turbo lol.

Misdiagnosed. The cabin air was the fix. They have to write it up as something different so that it doesn't get labeled as a comeback.

Hopefully it stays fixed for you..good luck !
 
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steiny93

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The cabin air filter was ABSOLUTELY NOT the fix.

At startup, hood open, the exhaust smell was horrible. Their was 100% a leak in the exhaust system.
The outstanding question will be if the smell we got after the turbo replace was only from residuals in the filter. That I don't know, time will tell.
 

DuraYuk

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The cabin air filter was ABSOLUTELY NOT the fix.

At startup, hood open, the exhaust smell was horrible. Their was 100% a leak in the exhaust system.
The outstanding question will be if the smell we got after the turbo replace was only from residuals in the filter. That I don't know, time will tell.
At least it's fixed now after the cabin air filter was replaced ;)

Hopefully the techs story was written well enough to avoid a charge back by GM.

If the turbo was actually leaking into the engine compartment you would have messed up 02 sensor logic as well as other tell tale signs.

If your happy that's all that matters. And it's fixed.
 

Chad G 1979

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I dont get how a cabin filter would make it smell like exhaust in the engine compartment with the hood open at start up.

As the cabin filter is inside the vehicle and filters air for inside the vehicle.

Yes after the turbo was replaced the filter still needed replaced after it had absorbed all the fumes from the engine from the leaky exhaust. So it still was part if the smell, but not the cause of the problem, just a symptom of the problem.
 

DuraYuk

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I dont get how a cabin filter would make it smell like exhaust in the engine compartment with the hood open at start up.

As the cabin filter is inside the vehicle and filters air for inside the vehicle.

Yes after the turbo was replaced the filter still needed replaced after it had absorbed all the fumes from the engine from the leaky exhaust. So it still was part if the smell, but not the cause of the problem, just a symptom of the problem.
If your vehicle is doing a regen you can smell it outside.

Im personally not convinced the turbo was leaking without the tell tale signs such as 02 sensor logic etc.

With that said I obviously wasn't there and don't know how the tech diagnosed it. A large visual leak would be accompanied by emissions codes and live data information.

The secondary issues leads me to believe there was more to it/misdiagnosed to begin with. Almost like a leak was introduced after the fact with the codes present and all.

The cabin air filter has been cause of some smells in the diesels. Not because of leaking turbos which is pretty damn rare in the baby max.

Regardless this is just online conjecture. Im glad OP got it fixed whatever the root cause actually may have been.
 
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steiny93

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I don't think you guys are understanding the course of events.

Issue 1: When the engine was running, exhaust smell happening in the cabin. If you got outside and opened the hood you could very clearly smell untreated diesel exhaust (not regen small). This was diagnosed as a leaking turbo via GM's smoke test procedure. (This exhaust was being sucked through the cabin air filter into the cabin)

Issue 2: After the turbo was replaced; continued to get an exhaust smell at startup (only in the cabin; for say 1 min). Tested the system for leaks, none found. They pulled the cabin air filter, it was stinky (from the previous untreated exhaust going through it). Filter changed, it doesn't smell now.

Issue 3: Check engine light, emissions, ect, sensor on turbo failed. They replaced the sensor and now those messages are gone.



A cabin air filter cannot be the root cause of an exhaust smell within the cabin. Changing a cabin filter will not fix an exhaust smell issue. Their has to be a leak in the exhaust system to get an exhaust smell into the cabin. (I'm not taking about regen smell, I'm taking untreated diesel exhaust smell)
 
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steiny93

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The cabin air filter has been cause of some smells in the diesels. Not because of leaking turbos which is pretty damn rare in the baby max.
This part doesn't make any sense. An exhaust smell doesn't originate within a filter, the contaminate has to be pulled through the filter first.
 

DuraYuk

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This part doesn't make any sense. An exhaust smell doesn't originate within a filter, the contaminate has to be pulled through the filter first.
It absolutely makes sense as it brings in outside air. Could be any vehicle that contaminates it.
 
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