2016 GMC SIERRA service trailer brake system

GMC Sierra Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-
9234758) - 2016 - crc - 11/9/15
154 Instruments and Controls
Brake System Messages
BRAKE FLUID LOW
This message is displayed when the
brake fluid level is low. SeeBrake
Fluid 0380.
SERVICE BRAKE ASSIST
This message may be displayed
when there is a problem with the
brake boost assist system. When
this message is displayed, the brake
boost assist motor might be heard
operating and you might notice
pulsation in the brake pedal. This is
normal under these conditions. Take
the vehicle to your dealer for
service.
SERVICE TRAILER BRAKE
SYSTEM
On vehicles with the Integrated
Trailer Brake Control (ITBC) system,
this message displays and a chime
may sound when there is a problem
with the ITBC system.
When this message displays, power
is no longer available to the trailer
brakes. As soon as it is safe to do so,
carefully pull your vehicle over to
the side of the road and turn the
ignition off. Check the wiring
connection to the trailer and turn the
ignition back on. If this message still
displays, either your vehicle or the
trailer needs service. See your
dealer.
See
“Integrated Trailer Brake
Control System” underTowing
Equipment 0339 for more
information.
Compass Messages
Dashes may be displayed if the
vehicle temporarily loses
communication with the Global
Positioning System (GPS).
Door Ajar Messages
DOOR OPEN
This message displays and a chime
may sound if a door is not fully
closed. Stop and turn off the
vehicle, check the door for obstructions, and close the door
again. Check to see if the message
still appears on the DIC.
HOOD OPEN
This message displays and a chime
may sound if the hood is not fully
closed. Stop and turn off the
vehicle, check the hood for
obstructions, and close the hood
again. Check to see if the message
still appears on the DIC.
Engine Cooling System
Messages
A/C OFF DUE TO HIGH
ENGINE TEMP
This message displays when the
engine coolant becomes hotter than
the normal operating temperature.
See
Engine Coolant Temperature
Gauge 0135. To avoid added strain
on a hot engine, the air conditioning
compressor automatically turns off.
When the coolant temperature
returns to normal, the air
conditioning compressor turns back
on. You can continue to drive your
vehicle.

GMC Sierra Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-
9234758) - 2016 - crc - 11/9/15
162 Instruments and Controls
Vehicle Reminder
Messages
CHECK TRAILER WIRING
On vehicles with the Integrated
Trailer Brake Control (ITBC) system,
this message may display and a
chime may sound when one of the
following conditions exists:
.A trailer with electric brakes
becomes disconnected from the
vehicle.
‐If the disconnect occurs while
the vehicle is stopped, this
message clears itself after a
short time.
‐ If the disconnect occurs while
the vehicle is moving, this
message stays on until the
ignition is turned off.
. There is a short in the wiring to
the electric trailer brakes.
When this message displays, power
is no longer available to the trailer
brakes. As soon as it is safe to do so,
carefully pull the vehicle over to the
side of the road and turn the ignition
off. Check the wiring connection to
the trailer and turn the ignition back
on. This message clears if the trailer
is reconnected. This message also
clears if you acknowledge it. If this
message still displays, either the
vehicle or the trailer needs service.
See your dealer.
See
“Integrated Trailer Brake
Control System” underTowing
Equipment 0339.
ICE POSSIBLE DRIVE
WITH CARE
This message displays when ice
conditions are possible.
TRAILER CONNECTED
On vehicles with the Integrated
Trailer Brake Control (ITBC) system,
this message displays briefly when
a trailer with electric or electric over
hydraulic brakes is first connected
to the vehicle. This message clears itself after
several seconds. This message also
clears if you acknowledge it. After
this message clears, the TRAILER
GAIN and OUTPUT displays appear
in the DIC.
See
Driver Information Center (DIC)
(Base Level) 0148 orDriver
Information Center (DIC) (Uplevel)
0 150 and“Integrated Trailer Brake
Control System” underTowing
Equipment 0339.
Vehicle Speed Messages
REDUCE SPEED FOR HILL
DESCENT CONTROL
This message displays when
attempting to enable Hill Descent
Control (HDC) when the vehicle
speed is too high. See Hill Descent
Control (HDC) 0305.

GMC Sierra Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-
9234758) - 2016 - crc - 11/9/15
Driving and Operating 325
If parking the rig on a hill:1. Press the brake pedal, but do not shift into P (Park) yet. Turn
the wheels into the curb if
facing downhill or into traffic if
facing uphill.
2. Have someone place chocks under the trailer wheels.
3. When the wheel chocks are in place, release the regular
brakes until the chocks absorb
the load.
4. Reapply the brake pedal. Then apply the parking brake and
shift into P (Park).
5. Release the brake pedal.
Leaving After Parking on a Hill
1. Apply and hold the brake pedal.
2. Start the engine.
3. Shift into a gear.
4. Release the parking brake.
5. Let up on the brake pedal.
6. Drive slowly until the trailer is clear of the chocks. 7. Stop and have someone pick
up and store the chocks.
Maintenance when Trailer
Towing
The vehicle needs service more
often when pulling a trailer. See
Maintenance Schedule 0454.
Things that are especially important
in trailer operation are automatic
transmission fluid, engine oil, axle
lubricant, belts, cooling system, and
brake system. It is a good idea to
inspect these before and during
the trip.
Check periodically to see that all
hitch nuts and bolts are tight.
Trailer Towing
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
If the vehicle is bi-fuel, see the
bi-fuel supplement.
Do not tow a trailer during break-in.
See New Vehicle Break-In 0277.
{Warning
The driver can lose control when
pulling a trailer if the correct
equipment is not used or the
vehicle is not driven properly. For
example, if the trailer is too heavy
or the trailer brakes are
inadequate for the load, the
vehicle may not stop as expected.
The driver and passengers could
be seriously injured. The vehicle
may also be damaged; the
resulting repairs would not be
covered by the vehicle warranty.
Pull a trailer only if all the steps in
this section have been followed.
Ask your dealer for advice and
information about towing a trailer
with the vehicle.
Caution
Pulling a trailer improperly can
damage the vehicle and result in
costly repairs not covered by the
(Continued)

GMC Sierra Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-
9234758) - 2016 - crc - 11/9/15
346 Driving and Operating
.There is a fault present in the
wiring to the trailer brakes (a
CHECK TRAILER WIRING
message will also display on
the DIC).
. The ITBC system is not working
due to a fault (a SERVICE
TRAILER BRAKE SYSTEM
message will also display in
the DIC).
Manual Trailer Brake Apply
The Manual Trailer Brake Apply
Lever is used to apply the trailer ’s
electric brakes independent of the
vehicle’s brakes. Sliding the lever to
the left will apply only the trailer
brakes. Use this lever to adjust
Trailer Gain to properly adjust the
power output to the trailer brakes.
The trailer's and the vehicle's brake
lamps will come on when either
vehicle brakes or manual trailer
brakes are applied. Trailer Gain Adjustment Procedure
Trailer Gain should be set for a
specific trailering condition and must
be adjusted anytime vehicle loading,
trailer loading, or road surface
conditions change.
{Warning
Trailer brakes that are
over-gained or under-gained may
not stop the vehicle and the trailer
as intended and can result in a
crash. Always follow the
instructions to set the Trailer Gain
for the proper trailer stopping
performance.
Use the following to adjust Trailer
Gain for each towing condition: 1. Drive the vehicle with the trailer attached on a level road
surface representative of the
towing condition and free of
traffic at about 32 to 40 km/h
(20 to 25 mph) and fully apply
the Manual Trailer Brake Apply
Lever. Adjusting Trailer Gain at
speeds lower than 32 to
40 km/h (20 to 25 mph) may
result in an incorrect gain
setting.
2. Adjust the Trailer Gain, using the Trailer Gain Adjustment
Buttons, 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.
3. Readjust Trailer Gain anytime vehicle loading, trailer loading,
or road surface conditions
change or if trailer wheel
lock-up is noticed at any time
while towing.

GMC Sierra Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-
9234758) - 2016 - crc - 11/9/15
Driving and Operating 347
Other ITBC-Related DIC Messages
In addition to displaying TRAILER
GAIN and OUTPUT through the
DIC, trailer connection and ITBC
system status are displayed on
the DIC.
TRAILER CONNECTED: This
message will briefly display when a
trailer with electric brakes is first
connected to the vehicle. This
message will automatically turn off
in about 10 seconds. This message
can be acknowledged before it
automatically turns off.
CHECK TRAILER WIRING: This
message will display if:
.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 30 seconds. This
message will also turn off if it is
acknowledged or if the trailer
harness is reconnected. 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 it is
acknowledged or if the trailer
harness is reconnected.
. There is an electrical fault in the
wiring to the trailer brakes. This
message will continue as long
as there is an electrical fault in
the trailer wiring. This message
will also turn off if it is
acknowledged.
To determine if the electrical fault is
on the vehicle side or trailer side of
the trailer wiring harness
connection: 1. Disconnect the trailer wiring harness from the vehicle.
2. Turn the ignition off.
3. Wait 10 seconds, then turn the ignition back to RUN.
4. If the CHECK TRAILER WIRING message reappears,
the electrical fault is on the
vehicle side. If the CHECK TRAILER
WIRING message only
reappears when connecting the
trailer wiring harness to the
vehicle, the electrical fault is on
the trailer side.
SERVICE TRAILER BRAKE
SYSTEM: This message will display
when there is a problem with the
ITBC system. If this message
continues over multiple ignition
cycles, there is a problem with the
ITBC system. Have the vehicle
serviced.
If either the CHECK TRAILER
WIRING or SERVICE TRAILER
BRAKE SYSTEM message displays
while driving, the ITBC system may
not be fully functional or may not
function at all. When traffic
conditions allow, carefully pull the
vehicle over to the side of the road
and turn the ignition off. Check the
wiring connection to the trailer and
turn the ignition back on. If either of
these messages continues, either
the vehicle or trailer needs service.

GMC Sierra Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-
9234758) - 2016 - crc - 11/9/15
Index 503
Messages (cont'd)Engine Oil . . . . . . . . . . . . . . . . . . . . 155
Engine Power . . . . . . . . . . . . . . . . 155
Fuel System . . . . . . . . . . . . . . . . . . 156
Key and Lock . . . . . . . . . . . . . . . . . 156
Lamp . . . . . . . . . . . . . . . . . . . . . . . . . 156
Object Detection System . . . . . 156
Ride Control System . . . . . . . . . . 157
Safety Belt . . . . . . . . . . . . . . . . . . . . 158
Security . . . . . . . . . . . . . . . . . . . . . . 159
Steering System . . . . . . . . . . . . . . 159
Tire . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Transmission . . . . . . . . . . . . . . . . . 160
Vehicle . . . . . . . . . . . . . . . . . . . . . . . 153
Vehicle Reminder . . . . . . . . . . . . . 162
Vehicle Speed . . . . . . . . . . . . . . . . 162
Washer Fluid . . . . . . . . . . . . . . . . . 163
Mirrors
Automatic Dimming . . . . . . . . . . . . . 48
Automatic DimmingRearview . . . . . . . . . . . . . . . . . . . . . . 50
Blind Spot . . . . . . . . . . . . . . . . . . . . . . 48
Convex . . . . . . . . . . . . . . . . . . . . . . . . . 45
Folding . . . . . . . . . . . . . . . . . . . . . . . . . 47
Heated . . . . . . . . . . . . . . . . . . . . . . . . . 48
Manual Rearview . . . . . . . . . . . . . . . 49
Power . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Tilt in Reverse . . . . . . . . . . . . . . . . . . 49 Mirrors (cont'd)
Trailer Tow . . . . . . . . . . . . . . . . . . . . . . 46
Mirrors, Interior Rearview . . . . . . . . 49
Monitor System, Tire Pressure . . . . . . . . . . . . . . . . . . . . . . 409
Multi-band Antenna . . . . . . . . . . . . . 199
N
Navigation OnStar®. . . . . . . . . . . . . . . . . . . . . . 487
New Vehicle Break-In . . . . . . . . . . . 277
Noise Control System . . . . . . . . . . 385
O
Object Detection System Messages . . . . . . . . . . . . . . . . . . . . . 156
Odometer . . . . . . . . . . . . . . . . . . . . . . . 133 Trip . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Off-Road . . . . . . . . . . . . . . . . . . . . . . . 261 Driving . . . . . . . . . . . . . . . . . . . . . . . . 261
Recovery . . . . . . . . . . . . . . . . . . . . . 260
Oil Engine . . . . . . . . . . . . . . . . . . . . . . . . 363
Engine Oil Life System . . . . . . . 366
Engine Oil Pressure Gauge . . . 134
Messages . . . . . . . . . . . . . . . . . . . . 155
Older Children, Restraints . . . . . . . 87
Online Owner Center . . . . . . . . . . . 475
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . 485 OnStar
®Additional
Information . . . . . . . . . . . . . . . . . . . . 490
OnStar
®Connections . . . . . . . . . . . 488
OnStar®Diagnostics . . . . . . . . . . . . 490
OnStar®Emergency . . . . . . . . . . . . 487
OnStar®Navigation . . . . . . . . . . . . . 487
OnStar®Overview . . . . . . . . . . . . . . 486
OnStar®Security . . . . . . . . . . . . . . . 487
Operating Mode Overheated EngineProtection . . . . . . . . . . . . . . . . . . . 377
Operation Fog Lamps . . . . . . . . . . . . . . . . . . . 179
Ordering Service Publications . . . . . . . . . . 481
Outlets
Power . . . . . . . . . . . . . . . . . . . . . . . . 126
Overheated Engine Protection Operating Mode . . . . 377
Overheating, Engine . . . . . . . . . . . . 375
Overview . . . . . . . . . . . . . . . . . . 186, 189
P
Pandora Internet Radio . . . . . . . . . 199
Park Shifting Into . . . . . . . . . . . . . . . . . . . 283
Shifting Out of . . . . . . . . . . . . . . . . 284
Parking Brake . . . . . . . . . . . . . . . . . . . . . . . . . 301