Question about a SOUND
 

So question. when you first turn the key to the on position. ( Not cranking it), there is a noise for a bout 2 to 3 seconds. Its hard to describe but kind of like a whine. Can you tell me what noise that is? (07Hummer h3x)

Probably the brake booster kicking in.

whatever it is..when i am parked at work on lunch break with the vehicle running. at different times I hear this noise again. and today..i was driving.. and was backed up in traffic at a 4 way stop..and i was hearing it a lot as i would ease forward and stop.

( I usually have my music up loud which is probably why i havent been hearing it before)

I've heard the noise as well, thought it was the fuel pump bringing the fuel rail up to pressure before cranking the engine. Never really thought more about it and considered it normal.

I'm just not sure if its normal to hear it as much as I am hearing it.. I thought for some reason it was the fuel pump also. but installed a brand new one a week ago.


I've been getting some random misfire codes sometimes when i am parked and the vehicle is running/idle. i just clear it and go on my way. But I was thinking it might have something to do with whats making this sound.

It is the electric brake booster/ABS pump.
It is completely normal.

ok thanks. so today i turned my music down today when i was in traffic for the 4 way stop and pretty much every time i hit the brakes to stop again..i heard it . its supposed to come on that much?

Did you check your fluid level?
How many miles? Might want to drain and refill with the proper fluid if you have high mileage or drive in stop and go all the time. Every fluid in a vehicle breaks down eventually. Heat and condensation are a brake systems enemy.

every time i ever checked before it was good.. so i will check it again. 54,000 miles.