GMC 2011 Sierra Denali Owner's Manual page 340

9-88 Driving and Operating
The power output to the trailer is
indicated in the Trailer Brake
Display Page on the DIC. If the
vehicle s service brakes are applied
while using the Manual Trailer Brake
Apply Lever, the trailer output power
will be the greater of the two.
The trailer's and the vehicle's brake
lamps will come on when either
vehicle braking or manual trailer
brakes are applied.
Trailer Gain Adjustment Procedure
Trailer Gain should be set for a
specific trailering condition and must
be adjusted any time vehicle
loading, trailer loading, or road
surface conditions change.
Setting the Trailer Gain properly is
needed for the best trailer stopping
performance. A trailer that is
over-gained may result in locked
trailer brakes. A trailer that is
under-gained may result in not
enough trailer braking. Both of these
conditions may result in poorer
stopping and stability of the vehicle
and trailer.
Use the following procedure to
correctly adjust Trailer Gain for each
towing condition:
1. Make sure the trailer brakes are
in proper working condition.
2. Connect a properly loaded
trailer to the vehicle and
make all necessary mechanical
and electrical connections.
See Vehicle Load Limits on
page 9 23 for more information.
3. After the electrical connection is
made to a trailer equipped with
electric brakes:
A TRAILER CONNECTED
message will be briefly
displayed on the DIC.
The Trailer Brake Display
Page will appear on the
DIC showing TRAILER
GAIN and TRAILER
OUTPUT.
In the Trailer Output Display
on the DIC, - - - - - - will
disappear if there is no
error present. Connecting a
trailer without electric
brakes will not clear the
six dashed lines.
4. Adjust the Trailer Gain by using
the gain adjustment (+ / -)
buttons on the Trailer Brake
Control Panel.