2016 Sierra Buzzing electronic sound when shut off

[MOhunter92]

When I shut my sierra off it makes an electronic buzzing motor kind of sound for about 5-10 seconds, does anybody know what this is and is it normal? 2016 SLT all terrain 5.3

 

 

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[SkiBum5.0]

I've always thought it was the entertainment/center stack making the noise. Like the head unit "powering off"

[MOhunter92]

I've always thought it was the entertainment/center stack making the noise. Like the head unit "powering off"

It is not anything inside making the noise, it's something near the front differential making the noise. It's a pump kind of sound, a loud whirring noise.

 

 

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[SkiDooNick700]

Also curious to know what this is, it is very noticeable if you pop the hood open immediately after turning it off. I don't remember for sure but I think you can even hit the unlock button and it'll do it, not 100% sure though. More than likely the electronic system just doin its thing.

[Black Denali Canada]

Is it the electric fans ? Or possibly the fuel pump you are hearing ?

 

 

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[MOhunter92]

Is it the electric fans ? Or possibly the fuel pump you are hearing ?

 

 

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I'm sure it could be one of them, I just don't understand why they turn on when I shut the truck off. Seems to only have started doing it when the weather got cold, but it's done it on the few warm days too

 

 

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[MOhunter92]

Also curious to know what this is, it is very noticeable if you pop the hood open immediately after turning it off. I don't remember for sure but I think you can even hit the unlock button and it'll do it, not 100% sure though. More than likely the electronic system just doin its thing.

Mine only does it when it gets shut off after a highway drive when it's cold out it seems

 

 

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[foghorn23]

Same here with the new 17 Denali. This sound has me stumped. I notice mine in the garage as it in an enclosed space and easier to hear. Always does it after shutdown. So far I've noticed all the posts in this thread are from Sierra drivers. Do the Silverado cousins do this as well?

[MOhunter92]

Same here with the new 17 Denali. This sound has me stumped. I notice mine in the garage as it in an enclosed space and easier to hear. Always does it after shutdown. So far I've noticed all the posts in this thread are from Sierra drivers. Do the Silverado cousins do this as well?

Yep that's when mine does it. Notice it most in garage, but it's also noticeable outside

 

 

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['17 Sierra]

It's an emissions thing from what I hear. Possibly the EGR system.

[MOhunter92]

It's an emissions thing from what I hear. Possibly the EGR system.

Interesting. I'll have to ask the tech who's been helping me with my truck.

 

 

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[DGBenny]

I'm in and out of my truck, without ever locking it or putting the keys in the ignition all day long at job sites. That noise happens sometimes when I open my door, with the truck just sitting there for hours.

[DLH]

I have the same issue with my 2016 GMC Sierra 5.3 SLT.  This noise has been intermittent since the truck was new, but happens after cutting the engine and getting out of the truck.  Sounds like it is coming from under the truck near the passenger door.  It usually stops after few minutes.  Sounds like a loud relay.  Last night I stopped driving about 8PM, had been on the road about 30 minutes, did not notice the noise when I came in from the garage.  Then about 10PM I went into the garage and I heard the sound, came back in and 5 minutes later, still heard the sound.  This morning I had a dead battery.  Jump started, had battery checked, and all is well with the battery.  I cannot get it to repeat.  I am confident whatever is making this noise drained the battery.  Dealer says I would have to leave it with them for a few days to see if they can hear it!  Any ideas, stuck relay, emissions, ABS?  One owner 68K miles.

[davevinc1080]

Sometimes I get that buzzing sound when i turn my truck off and open the door, or open the door in the morning before it is running. but it only lasts for 4-5 seconds and goes away. And it is very inconsistent. it has never drained the battery that i know of. Curios what it is. For me I am guessing some sort of a feedback loop with all the electronics in the vehicle when they are shutting down or starting up. JUST a guess. 

[Joe1981]

I have a 2016 Sierra as well.  I noticed that same buzz.  Sounds like a loud relay or transformer hum.  Also noticed red light around radio buttons.  I could go back in the truck and turn radio on without inserting or turning the key.  It has to be some sort of power/timer relay that supposed to kill power to radio after a certain amount of time.   But I’m a hvac tech.  Not a mechanic.  Guessing a trip to the dealership and a 300$ repair.  Three year old vehicles shouldn’t have issues.