Chevrolet 2009 Suburban Owner's Manual page 392

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.
2. Connect a properly loaded trailer to the vehicle
and make all necessary mechanical and electrical
connections. See Loading the Vehicle on page 4-33
for more information.
3. After the electrical connection is made to a trailer
equipped with electric brakes:
•
A TRAILER CONNECTED message will be
briefly displayed on the DIC display.
•
The Trailer Brake Display Page will appear on
the DIC showing TRAILER GAIN and TRAILER
OUTPUT.
4-64
•
In the Trailer Output display on the DIC, "- - - - - -"
will disappear if there is no error present.
Connecting a trailer without electric brakes
will not clear the six dashed lines.
4. Adjust the Trailer Gain by using the gain adjustment
(+ / −) buttons on the Trailer Brake Control Panel.
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