GMC 2010 Sierra 1500 Crew Cab Owner's Manual page 446

This symbol is located on the Trailer Brake Control
Panel on vehicles with an Integrated Trailer Brake
Control System. The power output to the trailer brakes
is based on the amount of brake pressure being applied
by the vehicle s brake system. This available power
output to the trailer brakes can be adjusted to a wide
range of trailering situations.
5-70
The vehicle may have an
Integrated Trailer Brake
Control (ITBC) system for
electric trailer brakes.
The ITBC system is integrated with the vehicle s brake,
anti lock brake and StabiliTrak (if equipped) systems.
In trailering conditions that cause the vehicle s anti lock
brake or StabiliTrak systems to activate, power sent to
the trailer's brakes will be automatically adjusted to
minimize trailer wheel lock-up. This does not imply that
the trailer has the StabiliTrak system.
If the vehicle s brake, anti lock brake or StabiliTrak
systems are not functioning properly, the ITBC system
may not be fully functional or may not function at all.
Make sure all of these systems are fully operational to
ensure full functionality of the ITBC system.
The ITBC system is powered through the vehicle's
electrical system. Turning the ignition off will also turn
off the ITBC system. The ITBC system is fully functional
only when the ignition is in ON or in RUN.
The ITBC system can only be used with trailers with
electric brakes.