Where is the airbag #3 sensor located in a 2008 silverado 2500hd 4wd

SOURCE: how do you remove headrest on a 2008 silverado?

1. Depress the button on the inboard head restraint guide to raise the head restraint to the full up position.
2. Insert a small diameter tool into the hole on the inboard side of the outboard head restraint guide and pull upward to remove.

SOURCE: where is the horn located under the hood of my 2008 chevy truck?

Have a friend, (or in-law) someone you're not too fond of, stand in front of the truck while you honk the horn and have them pinpoint it for you.

SOURCE: locate the oil sending unit on a 2003 6.0 2500HD silverado

You will find it down by the oil filter.

SOURCE: knock sensor location

The knock Sensors are located under the Intake Manifold at the top of your engine. The top will have to be taken off along with the intake manifold. Knock Sensors in past silverados used to have a problem with leaking water that corroded the sensors from washing the engine. Most times when you go to replace the knock sensor you will have to replace both along with the wiring harness that includes the the gaskets the knock sensors are surrounded by. After that you have to check the resistance to make sure you dont have any problems and then reinstall all parts along with a new intake manifold gasket. A good mechanic can do this for you in a day and charge you around $400. If you try to go to some place like a chevy dealer you will pay over $800. This is from experience of just replacing mine 2 weeks ago.

SOURCE: where is knock sensor located on 2004 chevy 2500Hd

Under intake manifold on top of block,you need to remove intake to access sensors there are two of them you can't miss them when intake is off. After replacing sensors you need a new intake gasket.