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Discussion Starter #1
Maybe someone can refresh my memory. When you cold start your Traverse it goes to high idle for abou 45 seconds or so. I always let my Traverse RPMs drop to 900 or so before I put my foot on the brake and shift into gear. Now, sometimes, my wife will not wait for the high idle to end, and she will just go ahead and press the brake pedal and shift into reverse. What is that TONE that you hear when you are still in high idle and you press the brake?
 

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Just a guess, but it's probably related to the fuel system while the injectors are delivering more fuel to help warm-up the engine quicker.
 

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while hes correct about the high idle and the 2 injector pulses for about 45 sec..
Im a little confused about the tone you speak of..
coming from speakers?
outside?
Parking assists?
Ive been close to my gate before and put it into reverse and im close enough that the system makes 1 long continous beeeeeepppp.
But sounds like youre hearing something else
 

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The vacuum like sound is the brake boost reservoir filling. This system is only used in emergency/heavy braking and will supply a quick burst of pressure to maximize breaking performance.
 

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Discussion Starter #5
BigBlue, that makes sense. I figured it had to do with the pressure in the brake lines. Because you only hear the "pump" noise when you depress the brake pedal BEFORE the idle levels drops down to under 1000 or so.
 

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Quantum-
I would be happy to research this for you. I would like to get more specific information from you regarding this issue. In order to do some further research, it would be very helpful to have the VIN of the vehicle as well as your full name and address for our records sent to me in an email. It would also be helpful to direct the message to Caron as well as mention that you were contacted on Yahoo Answers. Any assistance you can provide would be greatly appreciated. Thank you.

Michelle P, GM Customer Service
 

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Discussion Starter #7
Thanks Michelle, but I'm quite confident that the noise I am hearing is completely normal.
 

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BigBlueTraverse said:
The vacuum like sound is the brake boost reservoir filling. This system is only used in emergency/heavy braking and will supply a quick burst of pressure to maximize breaking performance.
agree....
 
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