Buzzing noise after a bump?

[treehan77]

Need some help. Twice now I’ve hit a large bump (railroad tracks) and hear a loud buzzing from what seems to be in the dash or possibly firewall area. It lasted about a second and a half. Best way I can describe it is the alarm from an old washing machine or dryer buzzing you that’s it’s done. Don’t notice any other symptoms, everything seems to working still. Ideas?

 

[Big Mama]

Any dash lights during this? It almost sounds like either a tire rub. Look at your inner fenders for a rub mark. If it’s an electronic sound see if your battery and grounds are secure.

 

[treehan77]

Definitely not tire rub. That doesn’t sound like a washing machine buzzer, and I redid all the shocks etc a while ago, had these tires for a couple of years. No dash lights, headlights were not on because it was sunny.

 

[Big Mama]

Ok sounds even more like a possible ground or wiring issue. These rigs are known to have grounding issues. The bump may be what starts the process. Check your battery grounds and the one by the passenger foot well.

 

[ncalvo]

maybe a weird noise from one of the hvac actuators

 

[treehan77]

Still monitoring. Still only happened twice. Best guess is stereo, who knows. If it would happen, I’d try with the stereo off but for now, I guess I wait

 

[Marky Dissod]

Need some help. Twice now I’ve hit a large bump (railroad tracks) and hear a loud buzzing from what seems to be in the dash or possibly firewall area.
It lasted about a second and a half. Best way I can describe it is the alarm from an old washing machine or dryer buzzing you that’s it’s done.
Don’t notice any other symptoms, everything seems to working still. Ideas?

Definitely not tire rub. That doesn’t sound like a washing machine buzzer, and I redid all the shocks etc a while ago, had these tires for a couple of years.
No dash lights, headlights were not on because it was sunny.

Still monitoring. Still only happened twice. Best guess is stereo, who knows. If it would happen, I’d try with the stereo off but for now, I guess I wait.

Once is never, twice is a coincidence, thrice is too often.
How long does this loud buzzing last? Less than 1sec, or more than 2sec?

 

[treehan77]

probably about a second a half. The first time it happened I wasn’t even sure it wasn’t sparking else’s car. Second time I had a passenger and we both knew it was mine for sure. Went over the same railroad tracks 4 times this weekend, couldnt reproduce it

 

[Marky Dissod]

maybe a weird noise from one of the hvac actuators?

This is what I think it is. Might've had something momentarily lose or make electrical contact immediately upon or after striking that bump.

 

[treehan77]

As good a guess as any I suppose. I have replaced a few of them over the years, last was the mode door one I think

 

[treehan77]

Still no recurrence of the mystery buzz. For now, I’m going to chalk it up to beta iPhone software.

 

[treehan77]

Buzzed at me for about a second again, this time just changing lanes. Wasn’t the stereo, was listening to a podcast it wasn’t interrupted or anything.

 

[Big Mama]

Could it be your lane keep assist setting?

 

[treehan77]

No, it is a 2005 lol

 

[Marky Dissod]

Could it be your lane keep assist setting?

Think of all the skills that we failed to pass down to next gen drivers ...
ABS? You were going too fast, dumbschidt, and pay better attention next time; every surprise is YOUR FAULT. Traction Control? See previous, buy better tires next time.
Stability Control? See previouses again, buy aftermarket suspension parts. What, you NEVER did parking lot doughnuts? Who let you think you could drive?

Even with Lane Keep Assist, inside the dotted lines, far too many people still weave like drunks.
Starting to get 'older', so I bought blind spot monitor mirrors at a car wash for $5, attached them to the upper outer corners of my side mirrors.

Enough of my ranting, back to you @treehan77.
You likely have a loose HVAC electrical connection, that's the most likely place where a brief buzzing would come from.

 

[Big Mama]

Think of all the skills that we failed to pass down to next gen drivers ...
ABS? You were going too fast, dumbschidt, and pay better attention next time; every surprise is YOUR FAULT. Traction Control? See previous, buy better tires next time.
Stability Control? See previouses again, buy aftermarket suspension parts. What, you NEVER did parking lot doughnuts? Who let you think you could drive?

Even with Lane Keep Assist, inside the dotted lines, far too many people still weave like drunks.
Starting to get 'older', so I bought blind spot monitor mirrors at a car wash for $5, attached them to the upper outer corners of my side mirrors.

Enough of my ranting, back to you @treehan77.
You likely have a loose HVAC electrical connection, that's the most likely place where a brief buzzing would come from.

And an interesting, to me anyway, side note. I recently traded a ‘23 Sierra 1500 for a ‘25 Sierra 2500. It has LKA but no steering correction, also no DFM or auto start/stop. The reason, according to GM, is the electric steering, DFM, and auto stop aren’t reliable enough for HD trucks. It also has an iron block instead of aluminum. Go figure. Everyone should get a 2500. They’re basically the same price.