GMC Yukon Owner's Manual page 424

5. Drive the vehicle with the trailer attached on a
level road surface representative of the towing
condition and free of traffic at about 20 to 25 mph
(32 to 40 km/h) and fully apply the Manual Trailer
Brake Apply lever.
Adjusting trailer gain at speeds lower than
20 to 25 mph (32 to 40 km/h) may result in an
incorrect gain setting.
6. Adjust the Trailer Gain to just below the point of
trailer wheel lock-up, indicated by trailer wheel
squeal or tire smoke when a trailer wheel locks.
Trailer wheel lock-up may not occur if towing a
heavily loaded trailer. In this case, adjust the
Trailer Gain to the highest allowable setting for
the towing condition.
7. Re-adjust Trailer Gain any time vehicle loading,
trailer loading or road surface conditions change or
if trailer wheel lock-up is noticed at any time while
towing
5-62
Other ITBC Related DIC Messages
In addition to displaying TRAILER GAIN and TRAILER
OUTPUT through the DIC, trailer connection and ITBC
system status is displayed in the DIC.
TRAILER CONNECTED
briefly displayed when a trailer with electric brakes
is first connected to the vehicle. This message will
automatically turn off in about ten seconds. The driver
can also acknowledge this message before it
automatically turns off.
CHECK TRAILER WIRING
displayed if:
1. The ITBC system first determines connection to
a trailer with electric brakes and then the trailer
harness becomes disconnected from the vehicle.
If the disconnect occurs while the vehicle is
stationary, this message will automatically turn off
in about thirty seconds. This message will also turn
off if the driver acknowledges this message off or if
the trailer harness is re-connected.
If the disconnect occurs while the vehicle is
moving, this message will continue until the ignition
is turned off. This message will also turn off if the
driver acknowledges this message off or if the
trailer harness is re-connected.
This message will be
This message will be