Why this noise?

[richardrocks]

When I merely open my door with key in pocket, a pump fires up briefly. Why? Often I’m just retrieving stuff from the truck.

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[richardrocks]

Part 2, why is this pump so dang loud? It’s always present upon start up (I’ve read about the transmission pumps) and it’s often sounding when I’m pulling into my garage. The video doesn’t quite capture how loud and ugly it sounds. So loud! Normal I suppose…

 

[Snakebitten]

The loudest pump I hear on mine is the brake booster pump, but I don't hear it if I take my foot off the brake pedal.
The electric parking brake isn't very stealthy either.

I'm not sure what all runs just from the truck waking up though.

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