GMC 2004 Sierra 1500 Pickup Owner's Manual page 181

To idle an automatic transmission equipped vehicle with
the DRL off, set the parking brake. Shifting the
transmission into PARK (P) will also allow you to idle
the vehicle with the DRL off. The DRL will stay off until
you release the parking brake or shift the transmission
out of PARK (P).
To idle a manual transmission equipped vehicle with the
DRL off, set the parking brake. The DRL will stay off
until you release the parking brake.
Fog Lamps
If your vehicle has fog lamps, use them for better vision
in foggy or misty conditions.
The fog lamp button is
located on the left side of
your instrument panel.
Your parking lamps and/or low-beam headlamps must
be on for your fog lamps to work.
Press the button to turn the fog lamps on. Press the
button again to turn them off. An indicator light will glow
in the button when the fog lamps are on.
Remember, fog lamps alone will not give off as much
light as your headlamps. Never use the fog lamps in the
dark without turning on the headlamps.
The fog lamps will go off whenever the high-beam
headlamps come on. When the high beams go off, the
fog lamps will come on again.
The fog lamps will be cancelled after the ignition is
turned off. If you still want to use the fog lamps after you
restart the vehicle, you will need to press the fog
lamp button again.
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