brake light GMC SIERRA 1500 2012 Owner's Manual
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Page 329 of 556
Black plate (53,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-53
Brakes
Antilock Brake
System (ABS)
This vehicle has the Antilock
Brake System (ABS), an advanced
electronic braking system that helps
prevent a braking skid.
When the engine is started and the
vehicle begins to drive away, ABS
checks itself. A momentary motor or
clicking noise might be heard while
this test is going on, and it might
even be noticed that the brake
pedal moves a little. This is normal.
If there is a problem with ABS, this
warning light stays on. SeeAntilock
Brake System (ABS) Warning Light
on page 5‑26. If driving safely on a wet road and it
becomes necessary to slam on the
brakes and continue braking to
avoid a sudden obstacle, a
computer senses that the wheels
are slowing down. If one of the
wheels is about to stop rolling, the
computer will separately work the
brakes at each wheel.
ABS can change the brake pressure
to each wheel, as required, faster
than any driver could. This can help
the driver steer around the obstacle
while braking hard.
As the brakes are applied, the
computer keeps receiving updates
on wheel speed and controls
braking pressure accordingly.
Remember: ABS does not change
the time needed to get a foot up to
the brake pedal or always decrease
stopping distance. If you get too
close to the vehicle in front of you,
there will not be enough time to
apply the brakes if that vehicle
suddenly slows or stops. Always
leave enough room up ahead to
stop, even with ABS.
Using ABS
Do not pump the brakes. Just hold
the brake pedal down firmly and let
ABS work. You might hear the ABS
pump or motor operating and feel
the brake pedal pulsate, but this is
normal.
Braking in Emergencies
ABS allows the driver to steer and
brake at the same time. In many
emergencies, steering can help
more than even the very best
braking.
Page 330 of 556
Black plate (54,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-54 Driving and Operating
Parking Brake
Set the parking brake by holding the
regular brake pedal down, then
pushing down the parking brake
pedal.
If the ignition is on, the brake
system warning light will come on.
SeeBrake System Warning Light on
page 5‑25.
Notice: Driving with the parking
brake on can overheat the brake
system and cause premature
wear or damage to brake system
parts. Make sure that the parking brake is fully released and the
brake warning light is off before
driving.
To release the parking brake, hold
the regular brake pedal down, then
push down momentarily on the
parking brake pedal until you feel
the pedal release. Slowly pull your
foot up off the parking brake pedal.
If the parking brake is not released
when you begin to drive, the brake
system warning light will flash and a
chime will sound warning you that
the parking brake is still on.
If you are towing a trailer and are
parking on a hill, see
Driving
Characteristics and Towing Tips on
page 9‑74.
Brake Assist
If this vehicle has StabiliTrak®, it
also has a Brake Assist feature
designed to assist the driver in
stopping or decreasing vehicle
speed in emergency driving
conditions. This feature uses the
stability system hydraulic brake control module to supplement the
power brake system under
conditions where the driver has
quickly and forcefully applied the
brake pedal in an attempt to quickly
stop or slow down the vehicle. The
stability system hydraulic brake
control module increases brake
pressure at each corner of the
vehicle until the ABS activates.
Minor brake pedal pulsation or
pedal movement during this time
is normal and the driver should
continue to apply the brake pedal
as the driving situation dictates
The Brake Assist feature will
automatically disengage when the
brake pedal is released or brake
pedal pressure is quickly
decreased.Hill Start Assist (HSA)
Non‐hybrid vehicles with StabiliTrak
have a Hill Start Assist (HSA)
feature, which may be useful when
the vehicle is stopped on a grade.
Page 331 of 556
Black plate (55,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-55
This feature is designed to prevent
the vehicle from rolling, either
forward or rearward, during vehicle
drive off. After the driver completely
stops and holds the vehicle in a
complete standstill on a grade, HSA
will be automatically activated.
During the transition period between
when the driver releases the brake
pedal and starts to accelerate to
drive off on a grade, HSA holds the
braking pressure for a maximum of
two seconds to ensure that there
is no rolling. The brakes will
automatically release when the
accelerator pedal is applied within
the two‐second window. If the
vehicle is equipped with the
Integrated Trailer Brake Control
(ITBC) system, HSA may also apply
the trailer brakes. It will not activate
if the vehicle is in a drive gear and
facing downhill or if the vehicle is
facing uphill and in R (Reverse).
There may be situations on minor
hills (less than 5% grade) with a
loaded vehicle or while pulling a
trailer where HSA will not activate.Ride Control Systems
StabiliTrak®System
The vehicle has a vehicle stability
enhancement system called
StabiliTrak. It is an advanced
computer-controlled system that
assists the driver with directional
control of the vehicle in difficult
driving conditions.
StabiliTrak activates when the
computer senses a discrepancy
between the intended path and the
direction the vehicle is actually
traveling. StabiliTrak selectively
applies braking pressure at any one
of the vehicle's brakes to assist the
driver with keeping the vehicle on
the intended path.
StabiliTrak is on automatically
whenever the vehicle is started. To
assist with directional control of the
vehicle, the system should always
be left on. Trailer Sway Control
(TSC) is also on automatically whenthe vehicle is started. See
Trailer
Sway Control (TSC) on page 9‑105
for more information.
When the vehicle is started and
begins to move, the system
performs several diagnostic checks
to insure there are no problems.
The system may be heard or felt
while it is working. This is normal
and does not mean there is a
problem with the vehicle. The
system should initialize before the
vehicle reaches 32 km/h (20 mph).
In some cases, it may take
approximately 3.2 km (2 mi) of
driving before the system initializes.
If cruise control is being used
when StabiliTrak activates, the
cruise control automatically
disengages. The cruise control
can be re-engaged when road
conditions allow. See Cruise Control
on page 9‑58.
If the system fails to turn on or
activate, the StabiliTrak light along
with a message will be displayed on
the Driver Information Center (DIC).
Page 332 of 556
Black plate (56,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-56 Driving and Operating
If a DIC message appears, make
sure the StabiliTrak system has not
been turned off using the Traction
Control System (TCS)/StabiliTrak
button. Then turn the vehicle off,
wait 15 seconds, and then turn it
back on again to reset the system.
If any of the messages still appear
on the DIC, the vehicle should be
taken in for service. For more
information on the DIC messages,
seeRide Control System Messages
on page 5‑44.
The StabiliTrak light will flash on the
instrument panel cluster when the
system or the TSC feature is both
on and activated.
The system may be heard or felt
while it is working; this is normal.
The TCS/StabiliTrak button is
located on the instrument panel.
The traction control part of
StabiliTrak can be turned off by
pressing and releasing the TCS/
StabiliTrak button if both systems
(traction control and StabiliTrak)
were previously on.
To disable both TCS and
StabiliTrak, press and hold the
TCS/StabiliTrak button until the
StabiliTrak OFF light illuminates and the appropriate DIC message
displays. This will also disable the
TSC feature.
Traction control and StabiliTrak
can be turned on by pressing and
releasing the TCS/StabiliTrak button
if they are not automatically shut off
for any other reason. This will also
enable the TSC feature.
When the TCS or StabiliTrak system
is turned off, the StabiliTrak light
and the appropriate message will be
displayed on the DIC to warn the
driver. The vehicle will still have
brake-traction control when traction
control is off, but will not be able to
use the engine speed management
system. See
“Traction Control
Operation” next for more
information.
When the TCS has been turned off,
system noises may still be heard as
a result of the brake-traction control
coming on.
Page 333 of 556
Black plate (57,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-57
It is recommended to leave the
system on for normal driving
conditions, but it may be necessary
to turn the system off if the vehicle
is stuck in sand, mud, ice or snow,
and you want to“rock”the vehicle to
attempt to free it. It may also be
necessary to turn off the system
when driving in extreme off-road
conditions where high wheel spin is
required. See If the Vehicle Is Stuck
on page 9‑15.
When the transfer case is in 4LO,
the stability system is automatically
disabled, the StabiliTrak light comes
on, and the appropriate message
will appear on the DIC. Both
traction control and StabiliTrak
are automatically disabled in this
condition.
Traction Control Operation
The TCS is part of the StabiliTrak
system. Traction control limits wheel
spin by reducing engine power
to the wheels (engine speed
management) and by applying brakes to each individual wheel
(brake-traction control) as
necessary.
The TCS is enabled automatically
when the vehicle is started. It will
activate and the StabiliTrak light
will flash if it senses that any of the
wheels are spinning or beginning to
lose traction while driving. If traction
control is turned off, only the
brake-traction control portion of
traction control will work. The
engine speed management will be
disabled. In this mode, engine
power is not reduced automatically
and the driven wheels can spin
more freely. This can cause the
brake-traction control to activate
constantly.
Notice:
If the wheel(s) of one axle
is allowed to spin excessively
while the StabiliTrak
®, ABS, brake
warning lights, and any relevant
DIC messages are displayed, the
transfer case could be damaged.
The repairs would not be covered
by the vehicle warranty. Reduce
engine power and do not spin the wheel(s) excessively while these
lights and messages are
displayed.
The TCS may activate on dry or
rough roads or under conditions
such as heavy acceleration while
turning or abrupt upshifts/downshifts
of the transmission. When this
happens, a reduction in acceleration
may be noticed, or a noise or
vibration may be heard. This is
normal.
If cruise control is being used when
the system activates, the StabiliTrak
light will flash and cruise control will
automatically disengage. Cruise
control may be reengaged when
road conditions allow. See
Cruise
Control on page 9‑58.
StabiliTrak may also turn off
automatically if it determines that a
problem exists with the system.
If the problem does not clear itself
after restarting the vehicle, see your
dealer for service.
Page 335 of 556
Black plate (59,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-59
I(On/Off):Press to turn the
system on or off. The indicator light
is on when cruise control is on and
turns off when cruise control is off.
+ RES (Resume/Accelerate):
Press briefly to resume to a
previously set speed, or press and
hold to accelerate.
SET −(Set/Coast): Press to set
the speed and activate cruise
control or make the vehicle
decelerate.
[(Cancel): Press to disengage
cruise control without erasing the
set speed from memory.
Setting Cruise Control
If the cruise button is on when not in
use, it could get bumped and go into
cruise when not desired. Keep the
cruise control switch off when cruise
is not being used.
The cruise control light on the
instrument panel cluster will come
on after the cruise control has been
set to the desired speed.
1. Press
I.
2. Get up to the desired speed.
3. Press the SET− button located
on the steering wheel and
release it.
4. Take your foot off the accelerator. Resuming a Set Speed
If the cruise control is set at a
desired speed and then the brakes
are applied, the cruise control is
disengaged without erasing the set
speed from memory.
Once the vehicle speed reaches
about 40 km/h (25 mph) or more,
press the +RES button on the
steering wheel. The vehicle returns
to the previous set speed and stays
there.
Increasing Speed While Using
Cruise Control
If the cruise control system is
already activated,
.Press and hold the +RES button
on the steering wheel until the
desired speed is reached, then
release it.
.To increase vehicle speed in
small amounts, press the
+RES button. Each time this is
done, the vehicle goes about
1.6 km/h (1 mph) faster.
Page 336 of 556
Black plate (60,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-60 Driving and Operating
Reducing Speed While Using
Cruise Control
If the cruise control system is
already activated,
.Press and hold the SET–button
on the steering wheel until the
desired lower speed is reached,
then release it.
.To slow down in small amounts,
press the SET– button on the
steering wheel briefly. Each time
this is done, the vehicle goes
about 1.6 km/h (1 mph) slower.
Passing Another Vehicle While
Using Cruise Control
Use the accelerator pedal to
increase the vehicle speed. When
you take your foot off the pedal,
the vehicle will slow down to the
previous set cruise speed.
Using Cruise Control on Hills
How well the cruise control works
on hills depends on the vehicle
speed, the load, and the steepness
of the hills. When going up steep hills, pressing the accelerator pedal
may be necessary to maintain
vehicle speed.
While going downhill:
.Vehicles with a four speed
automatic transmission may
need to have the brakes applied
or the transmission shifted
to a lower gear to keep the
speed down.
.Vehicles with a six speed
automatic transmission have a
Cruise Grade Braking feature
that may automatically shift to a
lower gear to keep the speed
down. It may be necessary to
apply the brake or manually
shift the transmission to a lower
gear. The vehicle may shift to a
higher gear when grade braking
assistance is no longer required.
Cruise Grade Braking is not
available while in Range
Selection Mode. This feature is
active when the exhaust brake
is enabled (if equipped). See
"Range Selection Mode" under
Manual Mode on page 9‑38.
When the brakes are manually
applied the cruise control is
disengaged.
Ending Cruise Control
There are three ways to end cruise
control:.To disengage cruise control;
step lightly on the brake pedal.
.Press[on the steering wheel.
.To turn off the cruise control,
press
Ion the steering wheel.
Erasing Speed Memory
The cruise control set speed
is erased from memory by
pressing
Ior if the ignition is
turned off.
Page 371 of 556
Black plate (95,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-95
Fifth-Wheel and Gooseneck
Trailering
Fifth-wheel and gooseneck trailers
can be used with many pickup
models. These trailers place a
larger percentage of the weight
(kingpin weight) on the tow vehicle
than conventional trailers. Make
sure this weight does not cause the
vehicle to exceed GAWR or GVWR.
Fifth-wheel or gooseneck kingpin
weight should be 15 to 25 percent of
the trailer weight up to the maximum
amount specified in the trailering
chart for the vehicle. See“Weight of
the Trailer” underTrailer Towing on
page 9‑78 for more information.
The hitch should be located in the
pickup bed so that its centerline is
over or slightly in front of the rear
axle. Take care that it is not so far
forward that it will contact the back
of the cab in sharp turns. This is
especially important for short box
pickups. Trailer pin box extensions
and sliding fifth-wheel hitch
assemblies can help this condition. There should be at least six inches
of clearance between the top of the
pickup box and the bottom of the
trailer shelf that extends over
the box.
Make sure the hitch is attached to
the tow vehicle frame rails. Do not
use the pickup box for support.
Safety Chains
Always attach chains between the
vehicle and the trailer. Cross the
safety chains under the tongue
of the trailer to help prevent the
tongue from contacting the road if it
becomes separated from the hitch.
Instructions about safety chains
may be provided by the hitch
manufacturer or by the trailer
manufacturer. If the trailer being
towed weighs up to 2 271 kg
(5,000 lbs) with a factory-installed
step bumper, safety chains may be
attached to the attaching points on
the bumper; otherwise, safety
chains should be attached to holes
on the trailer hitch platform. Always
leave just enough slack so the
combination can turn. Never allow
safety chains to drag on the ground.
Trailer Brakes
A loaded trailer that weighs more
than 900 kg (2,000 lbs) needs to
have its own brake system that is
adequate for the weight of the
trailer. Be sure to read and follow
the instructions for the trailer brakes
so they are installed, adjusted, and
maintained properly.
Do not tap into the vehicle's
hydraulic brake system.
Auxiliary Battery
The auxiliary battery provision can
be used to supply electrical power
to additional equipment that may be
added, such as a slide-in camper.
If the vehicle has this provision, this
relay will be located on the driver
side of the vehicle, next to the
underhood electrical center.
Page 373 of 556
Black plate (97,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
Driving and Operating 9-97
.Red: Battery Feed*
.Dark Blue: Trailer Brake*
*The fuses for these two circuits are
installed in the underhood electrical
center, but the wires are not
connected. They should be
connected by your dealer or a
qualified service center. The fuse
and wire for the ITBC is factory
installed and connected if the
vehicle is equipped with an ITBC.
The fuse for the battery feed is not
required if the vehicle has an
auxiliary battery. If the vehicle does
not have an auxiliary battery, have
your dealer or authorized service
center install the required fuse.
If charging a remote (non-vehicle)
battery, press the Tow/Haul Mode
button, if equipped, located at
the end of the shift lever. This will
boost the vehicle system voltage
and properly charge the battery.
If the trailer is too light for Tow/
Haul Mode, or the vehicle is not
equipped with Tow/Haul, turn on the headlamps as a second way to
boost the vehicle system and
charge the battery.
Camper/Fifth-Wheel Trailer Wiring
Package
The seven-wire camper harness is
located under the front edge of the
pickup box on the driver side of
the vehicle, attached to the frame
bracket. A connector must be
added to the wiring harness which
connects to the camper.
The harness contains the following
camper/trailer circuits:
.Yellow: Left Stop/Turn Signal
.Dark Green: Right Stop/Turn
Signal
.Brown: Taillamps
.White: Ground
.Light Green: Back-up Lamps
.Red: Battery Feed
.Dark Blue: Trailer Brake
If the vehicle is equipped with the
“Heavy-Duty Trailering”
option,
please refer to “Heavy-Duty Trailer
Wiring Package” earlier in this
section.
When the camper-wiring harness
is ordered without the heavy-duty
trailering package, a seven-wire
harness with a seven-pin connector
is located at the rear of the vehicle
and is tied to the vehicle's frame.
Page 374 of 556
Black plate (98,1)GMC Sierra Owner Manual - 2012 - CRC - 11/15/11
9-98 Driving and Operating
Electric Brake Control Wiring
Provisions
These wiring provisions are
included with the vehicle as part of
the trailer wiring package. These
provisions are for an electric brake
controller. The instrument panel
contains blunt cut wires behind the
steering column for the trailer brake
controller. The harness contains the
following wires:
.Dark Blue: Brake Signal to
Trailer Connector
.Red/Black: Battery
.Light Blue/White: Brake Switch
.White: Ground
The harness should be installed by
your dealer or a qualified service
center.
If the vehicle is equipped with an
Integrated Trailer Brake Control
(ITBC) System, the blunt cuts exist,
but are not connected further in the harness. If an aftermarket trailer
brake controller is installed, the
ITBC must be disconnected. Do not
power both ITBC and aftermarket
controllers to control the trailer
brakes at the same time.
Tow/Haul Mode
Pressing this button at the end of
the shift lever turns on and off the
Tow/Haul Mode.
This indicator light on the instrument
panel cluster comes on when the
Tow/Haul Mode is on.
Tow/Haul is a feature that assists
when pulling a heavy trailer or a
large or heavy load. See
Tow/Haul
Mode on page 9‑39 for more
information.
Tow/Haul is designed to be most
effective when the vehicle and
trailer combined weight is at least
75 percent of the vehicle's Gross
Combined Weight Rating (GCWR).
See “Weight of the Trailer” under
Trailer Towing on page 9‑78. Tow/
Haul is most useful under the
following driving conditions:
.When pulling a heavy trailer or
a large or heavy load through
rolling terrain.