GMC Yukon XL Denali Owner's Manual page 313

Trailer Sway Control (TSC) on
page 9 35 and Hill Start Assist
(HSA) on page 9 35.
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).
Manual Trailer Brake Apply
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 in 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 and the vehicle's brake
lamps will come on when either
vehicle braking or manual trailer
brakes are applied.
Driving and Operating
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.
9-69