Buzzing sound upon opening driver door

That's the vacuum pump for the brakes. The car needs to have an electric pump so that the brake assist works when the engine is off.

 

I don't think it's a vacuum pump, but it is a pump. It's pressurizing the brake system.

 

ABS pressurization pump.

 

The same noise occurs when I open my 2015 Prius car door. Is there any action I should take to fix this, or is it something I can leave be without worrying about?

 

Ignore. Normal. Sometimes you hear it as you walk up to the car without even touching it. Sometimes several seconds after exiting the car.

 

The only time to worry would be if you don't hear it.

That's your brake accumulator pump, building up the brake fluid pressure for you so that you will be able to slow and stop the car at times of your choosing. They think of everything, these guys.

-Chap

 

Woohoo, thank you!

Glad to hear it, thanks!

 

I also noticed that the buzzing sounds repeats itself every 30 sec or so while driving. Is it normal? Same pump?

 

yes and no

it has to keep repressuizing, but increased frequency means the system is slowly failing

 

Or you have an ABS system leak-down, whether in the pump or elsewhere.

 

Would I get a warning light because of that?

 

If there is a leak, I should see a spot where I park, no? That is not the case though. Would I get a warning light it that is the case?

 

it doesn't leak out. sometimes there is a warning, sometimes the brakes operate more like manual than power.

 

This would not be an external leak, it would be an internal leak past seals, a loss of pressurization that requires frequent re-pumping up to operating pressure parameters.