GMC 2009 Envoy Denali Owner's Manual page 301

The seven-wire harness contains the following trailer
circuits:
•
Yellow: Left Stop/Turn Signal
•
Dark Green: Right Stop/Turn Signal
•
Brown: Running Lamps
•
White: Ground
•
Light Green: Back-up Lamps
•
Red: Battery Feed
•
Dark Blue: Electric Brakes
If towing a light-duty trailer with a standard four-way
round pin connector, an adapter connector is available
from your dealer/retailer.
If charging a remote (non-vehicle) battery, turn on the
headlamps to boost the vehicle system voltage and
properly charge the battery.
The vehicle is also equipped with wiring for an
electric trailer brake controller. These wires are
located inside the vehicle on the driver side under the
instrument panel. These wires should be connected
to an electric trailer brake controller by your
dealer/retailer or a qualified service center.
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