GMC 2012 Sierra Denali Owner's Manual page 324

To adjust the Trailer Gain, press one
of the Trailer Gain adjustment
buttons located on the Trailer Brake
Control Panel. Press and hold a
gain button to cause the Trailer Gain
to continuously adjust. To turn the
output to the trailer off, adjust the
Trailer Gain setting to 0.0 (zero).
0.0 (zero) gain is the factory default
setting. To properly adjust trailer
gain, see Trailer Gain Adjustment
Procedure later in this section.
TRAILER OUTPUT: This is
displayed any time a trailer with
electric brakes is connected. Output
to the electric brakes is based on
the amount of vehicle braking
present and relative to the Trailer
Gain setting. Output is displayed
from 0 to 10 bars for each gain
setting.
Vehicles with Trailer Sway Control
(TSC) or Hill Start Assist (HSA),
output to the electric trailer brakes
may be displayed when the systems
are active. See
and
The Trailer Output will
indicate - - - - - - on the
Trailer Brake Display Page
whenever the following occur:
No trailer is connected
A trailer without electric brakes
is connected (no DIC message
is displayed)
A trailer with electric brakes
has become disconnected
(a CHECK TRAILER WIRING
message will also be displayed
on the DIC)
There is a fault present in the
wiring to the electric trailer
brakes (a CHECK TRAILER
WIRING message will also be
displayed on the DIC)
There is a fault in the ITBC
system (a SERVICE TRAILER
BRAKE SYSTEM message will
also be displayed in the DIC)
The Manual Trailer Brake Apply
.
Lever is located on the Trailer Brake
Control Panel and is used to apply
the trailer s electric brakes
independent of the vehicle s brakes.
This lever is used in the Trailer Gain
Adjustment Procedure to properly
adjust the power output to the trailer
brakes. Sliding the lever to the left
will apply only the trailer brakes.
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.