GMC 1998 Savana Van Owner's Manual page 114

The DRL system will make your headlamps come on at
a reduced brightness when:
The ignition is on,
The headlamp switch is off, and
The parking brake is released.
When the DRL are on, only your headlamps will be on.
The taillamps, sidemarker and other lamps won't be on.
Your instrument panel won't be lit up either.
When it begins to get dark, your DRL indicator light is
a reminder to turn your headlamp switch on. The other
lamps that come on with your headlamps will also
come on.
When you turn off the headlamp switch, the regular
lamps will go off, and your headlamps will change to
the reduced brightness of DRL.
To idle your vehicle with the engine on and the DRL off,
set the parking brake. The DRL will stay off until you
release the parking brake.
As with any vehicle, you should turn on the regular
headlamp system when you need it.
Center High-Mounted Stoplamp
Your vehicle's center high-mounted stoplamp is located
above the rear doors at the center of the vehicle.
If items are loaded on
the roof of the vehicle, as in a
luggage carrier, care should be taken not to block or
damage the center high-mounted stoplamp unit.
If you tow a trailer that is equipped with provisions for a
center high-mounted stoplamp, see your GM dealer for
instructions on how to make it operate with your
vehicle's electrical system. As with any electrical system
modification, have the work performed by a qualified
electrical service person.
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