Were is the idle air control valve located on a 1999 chevy k1500

SOURCE: no air

there are 2 of them one is at the reciever dryer inside the engine compartment (its inside the low pressure side ac line) the other is inside the unit in the rear and is a different style with a cap tube attached

SOURCE: Can you please tell me where the speed sensor is

There are several different combination's of engines and transmissions on these trucks. They may be in slightly different locations depending on your configuration.
4x4 GM trucks will be mounted in the tailstock of the transfer case. This is just ahead of where the rear driveshaft enters the case. They are a 2 wire hall effect sensor and most are easy to replace.

SOURCE: How to locate idle air control valve?

It's located on the left rear of throttle body assembly. I looks like a small metal cylinder with two bolts and an oval plug with 4 prongs. Yes you can change it yourself. If you can't find it, go to your local auto parts store and have them show you a picture.

SOURCE: Where is the idle air control valve located in a

You'll need to remove the interior engine cover(dog house).Torx screws for the covers, 2 bolts on floor. and bolts against the fire wall (i use a long extension with a swivel socket at the end). The IAC valve is screwed in to the side of the throttle housing (where the gas pedal hooks up to the engine).I can get a pic if you need it.

SOURCE: where is heater control valve

Does not have one, has a door that separates heater core from the rest of a/c box in dash.