Chevrolet Kodiak 2006 Owner's Manual page 113

Vehicles built for use as tractors or towing vehicles have
two air brake controls. They look like this:
CAUTION:
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When the yellow PARKING BRAKE and the red
TRAILER AIR SUPPLY knobs are both pushed
in, your rig will be free to move. It could strike
someone or something. When both of these
knobs are pushed in, hold the regular brake
pedal down to keep your rig from moving.
To charge a trailer's air brake system do the following:
1. Move your vehicle into the proper position.
2. Apply the parking brake by pulling the yellow
parking brake knob out.
3. Hook up the trailer air system properly.
4. Get into the vehicle.
5. Push and hold down the regular brake pedal.
6. Push in both the yellow parking brake and the red
trailer air supply knobs. This will charge your
trailer's air system.
After a few minutes, the trailer system should be fully
charged. When it is, the air pressure gage will show
about 125 to 135 psi (862 to 931 kPa). See Air Pressure
Gage on page 3-47 for more information.
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