Chevrolet 2003 Tahoe Owner's Manual page 166

Daytime Running Lamps
Daytime Running Lamps (DRL) can make it easier for
others to see the front of your vehicle during the
day. BRL can be helpful in many different driving
conditions, but they can be especially helpful in the short
periods after dawn and before sunset. Fully functional
daytime running lamps are required on all vehicles
first sold in Canada.
The DRL system will come on when the following
conditions are met:
the ignition is on,
the exterior lamps control is AUTO,
the automatic transmission is not in PARK (P),
the light sensor determines it is daytime and
When the DRL are on, only your DRL lamps will be on.
The taillamps, sidemarker and other lamps won't be
on. The instrument panel won't be lit up either.
When it begins to get dark, the automatic headlamp
system will switch from DRL to the headlamps or the last
chosen headlamp setting that was used.
When you turn the headlamp switch off, the headlamps
will go off, and your DRL lamps will illuminate,
provided it is not dark outside.
Shifting the transmission into PARK (P) will allow you to
idle the vehicle with the DRL off. The DRL will stay
off until you shift the transmission out of PARK (P).
This procedure applies only to vehicles first sold in the
United States.
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
the instrument panel.
of
Your parking lamps and/or low-beam headlamps must
be on for your fog lamps to work.
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