Need diagram for replacing the serpentine belt on chevy implala 06' 3.9

you did not specify what engine.
google 2009 chevy impala serpentine belt Diagram


copy and paste

https://www.justanswer.com/chevy/3ruw6-need-serpentine-belt-diagram-2006-chevy-3-5-lt.html

https://www.fixya.com/cars/t15630016-diagram_serpentine_belt_2009_impala_3_5l

Belt diagram is down at the bottom for Chevy trucks

https://www.google.com/search?q=serpentine+belt+on+my+1989+Chevy+Shasta+G30+rv

..

There should be a diagram sticker on the hood or the fan shroud.
You can also draw a diagram before you remove the old belt.
There is a spring loaded tensioner you move over to release pressure on the belt.
I can upload a diagram if you can't find the sticker.

You use a breaker bar to move the tensioner, remove the belt and use the tensioner to put it back. You draw the belt and pulleys on a sheet of paper before removing, otherwise there should be a small diagram of the belt and pulley positions on the fan shroud or radiator support.

Diagram should be under the hood
The auto tensioneris down low and dificult to get to.
If it has not been changed in a while you will need a long thin push stick and a serpentine tool.
Push on the belt hard at the auto adjuster and pop the belt off the smooth pully (located top).
hook up the serpentine belt tool and then mount the new belt

check your frame for the diagram or go to google images look up 1997 Chevy Cheyenne C2500 w/5.7L V8 serpentine belt diagram they will have it might not be the first pic

diagram should be on the radiator shroud / top of radiator

First, keep this diagram around as you will need it to route the serpentine belt when you reinstall it. There may also be a diagram under the hood by the radiator.
Next, follow this link and watch the video that shows you how to replace a serpentine belt...
http://www.wonderhowto.com/how-to/video/how-to-inspect-and-replace-your-car-s-serpentine-belt-267229/

My sincere apologies for the delayed response.
I am personally going back to answer your unanswered questions.

I do not know if you still need this information, but I am going ahead and answering it anyway. You may want to Print the Diagrams for future use.

I am assuming this "van" is a Chevy Venture?
CLICK on the following LINK. It has the Belt Diagrams you will need.
If you would: Before Clicking: Let me know if this helped you, or if you have any additional information or questions. Feel Free to contact me at FixYa.com!
Again my apologies...
http://www.2carpros.com/car_repair_information/year/2000/make/chevrolet/model/venture/2000_chevrolet_venture_drive_belt_routing_diagram.htm