GMC Sierra 2008 Owner's Manual page 380

Trailer Brake Control Panel
A. Manual Trailer Brake Apply Lever
B. Trailer Gain Adjustment Buttons
4-78
The ITBC system has a control panel located on the
instrument panel to the left of the steering column.
See Instrument Panel Overview (Base/Uplevel version)
on page 3-4 or Instrument Panel Overview (Premium
version) on page 3-6 for more information on location.
The control panel allows you to adjust the amount
of output, referred to as trailer gain, available to
the electric trailer brakes and allows you to manually
apply the trailer brakes. The Trailer Brake Control
Panel is used along with the Trailer Brake Display
Page on the DIC to adjust and display power output
to the trailer brakes.
Trailer Brake DIC Display Page
The ITBC system displays messages into the vehicle's
Driver Information Center (DIC). See DIC Warnings
and Messages on page 3-67 for more information.