I've been trying to find out what this part is? It's never come on and when key is on ACC (turned all the way without starting) This parts comes on and sounds like a vacuum sound.
Does anyone know what this part is?

 

Vaccum pump.

 

Diesels don't make vacuum like naturally aspirated gas cars so they need a separate vacuum pump. It's used to operate the HVAC system and engage the auto-locking 4x4 hubs.

They can be either mechanical or electric. 6.0 uses an electric which you've found.

 

Thanks guys. Just found out corrupted Tuner software. Will know more on Tuesday.