What length serpentine belt is a 2006 Chevy Silverado with a 6.6 liter duramax engine need?

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

Different model year shown but it is the same engine. The diagram should also be located on the shroud above your radiator. 2006 Chevrolet Silverado 3500 V8 8 1L Serpentine Belt Diagram...

Is this what you need? You said serpentine belt but my info showed three belts. If picture is wrong let me know.

Audi a4 a6 2 8 Serpentine Belt OEM ContiTech

1996 AUDI A6 Serpentine Belt Diagram for V6 2 8 Liter Engine Serpentine...

http://serpentinebelt-replacement.com/1996AudiA6SerpentineBeltReplacement

Audi Accessory Belts

you may still have the decal under the hood somewhere that shows the belt routing look for it, it should be there.

a fault with crankshaft position sensor will cause a no injector pulse on your 2006 chevy silverado 2500HD with the 6.0 Liter engine. have you checked your diagnostic trouble codes

You need a dealer, there is a real problem going on here, way over the head of any home do it yourselfer. The main reason is the special tools required to interface with the control modules that are throwing these codes

Here's a picture.

Pop the hood of the car and locate the serpentine belt routing diagram. The diagram on the 2003 Chevrolet Impala is on top of the fan shroud. The diagram will be a picture of all of the accessory pulleys and how the serpentine belt is routed among the pulleys. This diagram will give you the exact direction for routing the new belt onto the pulleys. If you cannot find a serpentine belt routing diagram, take a notepad and pen and draw out the exact routing diagram of the old belt across the pulleys.

2 Locate the serpentine belt tensioner. It is located below the alternator on the left front side of the engine. The tensioner on the 3.4 liter, 3.5 liter and the 3.9 liter engines will require a 3/8 ratchet to release the belt tensioner. The 3.8 liter engine will require a ratchet and a 15 mm socket for the belt tensioner. Rotate the belt tensioner clockwise to loosen and remove the belt from the belt tensioner pulley.

3 Slide the old belt from the belt tensioner pulley. Remove the belt from the remaining pulleys and pull the belt from the engine compartment.

4 Route the new belt across the crankshaft pulley first. The crankshaft pulley is the big pulley on the bottom of the engine in the center. Then route the serpentine belt across the remaining pulleys as directed by the serpentine belt routing diagram. Leave the belt tensioner pulley for last.

5 Rotate the belt tensioner clockwise again to relieve the tension and slide the new belt across the top of the belt tensioner pulley. Release the belt tensioner and the belt will tighten up as the tensioner applies pressure to the belt. Make sure the new belt is properly seated in all the pulleys.

6 Crank the engine and inspect the belt again to make sure that it stays seated in the pulleys.

Read more: How to Replace a Serpentine Belt on a 2003 Chevrolet Impala ' eHow.co.uk http://www.ehow.co.uk/how_6120665_replace-belt-2003-chevrolet-impala.html#ixzz1Yi6QLAjb

check belt tensioner pulley for worn bearings.check that belt is not worn beyond serviceable length,has cracks or is frayed.