brake GMC YUKON XL 2007 Owner's Guide

Control of a Vehicle
You have three systems that make your vehicle
go where you want it to go. They are the brakes,
the steering, and the accelerator. All three
systems have to do their work at the places where
the tires meet the road.
Sometimes, as when you are driving on snow or
ice, it is easy to ask more of those control systems
than the tires and road can provide. That means
you can lose control of your vehicle. See
StabiliTrak
®System on page 348.
Adding non-GM accessories can affect your
vehicle’s performance. SeeAccessories and
Modications on page 426.
Braking
SeeBrake System Warning Light on page 232.
Braking action involves perception time and
reaction time.
First, you have to decide to push on the brake
pedal. That is perception time. Then you have to
bring up your foot and do it. That is reaction time.Average reaction time is about three-fourths of a
second. But that is only an average. It might
be less with one driver and as long as two or
three seconds or more with another. Age, physical
condition, alertness, coordination, and eyesight
all play a part. So do alcohol, drugs, and
frustration. But even in three-fourths of a second,
a vehicle moving at 60 mph (100 km/h) travels
66 feet (20 m). That could be a lot of distance in an
emergency, so keeping enough space between
your vehicle and others is important.
And, of course, actual stopping distances vary
greatly with the surface of the road, whether it is
pavement or gravel; the condition of the road,
whether it is wet, dry, or icy; tire tread; the
condition of your brakes; the weight of the vehicle;
and the amount of brake force applied.
Avoid needless heavy braking. Some people drive
in spurts — heavy acceleration followed by
heavy braking — rather than keeping pace with
traffic. This is a mistake. Your brakes may
not have time to cool between hard stops. Your
brakes will wear out much faster if you do a lot of
heavy braking.
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If you keep pace with the traffic and allow realistic
following distances, you will eliminate a lot of
unnecessary braking. That means better braking
and longer brake life.
If your engine ever stops while you are driving,
brake normally but do not pump your brakes.
If you do, the pedal may get harder to push down.
If your engine stops, you will still have some
power brake assist. But you will use it when you
brake. Once the power assist is used up, it
may take longer to stop and the brake pedal will
be harder to push.
Adding non-GM accessories can affect your
vehicle’s performance. SeeAccessories and
Modications on page 426.Anti-Lock Brake System (ABS)
Your vehicle has the Anti-Lock Brake System
(ABS), an advanced electronic braking system that
will help prevent a braking skid.
When you start your engine and begin to drive
away, ABS will check itself. You may hear a
momentary motor or clicking noise while this test
is going on. This is normal.
If there is a problem
with ABS, this warning
light will stay on.
SeeAnti-Lock Brake
System Warning
Light on page 233.
Along with ABS, your vehicle has a Dynamic Rear
Proportioning (DRP) system. If there is a DRP
problem, both the brake and ABS warning lights will
come on accompanied by a 10-second chime. The
lights and chime will come on each time the ignition
is turned on until the problem is repaired. See your
dealer for service.
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Let us say the road is wet and you are driving
safely. Suddenly, an animal jumps out in front of
you. You slam on the brakes and continue braking.
Here is what happens with ABS:
A computer senses that wheels are slowing down.
If one of the wheels is about to stop rolling, the
computer will separately work the brakes at each
front wheel and at both rear wheels.
ABS can change the brake pressure faster than
any driver could. The computer is programmed to
make the most of available tire and road
conditions. This can help you steer around the
obstacle while braking hard.
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As you brake, your computer keeps receiving
updates on wheel speed and controls braking
pressure accordingly.
Remember: ABS does not change the time you
need to get your foot up to the brake pedal or
always decrease stopping distance. If you get too
close to the vehicle in front of you, you will not have
time to apply your brakes if that vehicle suddenly
slows or stops. Always leave enough room up
ahead to stop, even though you have ABS.
Using ABS
Do not pump the brakes. Just hold the brake
pedal down rmly and let anti-lock work for you.
You may feel the brakes vibrate, or you may notice
some noise, but this is normal.
Braking in Emergencies
With ABS, you can steer and brake at the same
time. In many emergencies, steering can help you
more than even the very best braking.
Locking Rear Axle
If your vehicle has this feature, your locking rear
axle can give you additional traction on snow, mud,
ice, sand or gravel. It works like a standard axle
most of the time, but when one of the rear wheels
has no traction and the other does, this feature will
allow the wheel with traction to move the vehicle.
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StabiliTrak®System
Your vehicle may be equipped with the
StabiliTrak®system which combines antilock
brake, traction and stability control systems and
helps the driver maintain directional control of the
vehicle in most driving conditions.
When you rst start your vehicle and begin to drive
away, the system performs several diagnostic
checks to ensure there are no problems. You may
hear or feel the system working. This is normal and
does not mean there is a problem with your vehicle.
The system should initialize before the vehicle
reaches 20 mph (32 km/h). In some cases, it may
take approximately two miles of driving before the
system initializes.
If the system fails to turn on or activate, the
StabiliTrak
®light along with one of the following
messages will be displayed on the Driver
Information Center (DIC) (TRACTION CONTROL
OFF, SERVICE TRACTION CONTROL,
STABILITRAK OFF, SERVICE STABILITRAK).
For 2500 series vehicles, if the vehicle has gone
through heavy acceleration or braking during
the rst 2 miles (3.2 km) after starting your vehicle,
these messages may also appear.For 1500 series vehicles, if these DIC messages
appear, make sure the StabiliTrack
®system
has not been turned off, then turn the steering
wheel through either the ten or two o’clock
positions. If this does not clear the message(s),
take your vehicle to the dealer for service. If this is
the case, your vehicle does not need servicing.
Turn your vehicle off and back on again to
reset the system. If any of these messages appear
on the Driver Information Center (DIC), and your
vehicle hasn’t gone through hard acceleration
or braking in the rst two miles, your vehicle
should be taken in for service. For more
information on the DIC messages, seeDriver
Information Center (DIC) on page 244.
The StabiliTrak
®light
will ash on the
instrument panel cluster
when the system is
both on and activated.
You may also feel or hear the system working;
this is normal.
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The traction control
disable button is located
on the instrument
panel below the climate
controls.
The traction control part of StabiliTrak
®can be
turned off by pressing and releasing the
StabiliTrak
®button if both systems (traction control
and StabiliTrak®) were previously on. To disable
both traction control and StabiliTrak®, press
and hold the button for ve seconds.
Traction control and StabiliTrak
®can be turned on
by pressing and releasing the StabiliTrak®
button if both systems were previously off, if not
automatically shut off for any other reason.
When the system is turned off, the TRACTION
CONTROL OFF message and the StabiliTrak
®
light will appear to warn the driver that both
the traction control and part of StabiliTrak®are
disabled. Your 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 traction control system has been turned
off, you may still hear system noises as a result
of the brake-traction control coming on.
It is recommended to leave the system on for
normal driving conditions, but it may be necessary
to turn the system off if your vehicle is stuck in
sand, mud, ice or snow, and you want to
“rock” your 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. SeeIf Your Vehicle is
Stuck in Sand, Mud, Ice, or Snow on page 388.
When the transfer case is in 4LO, the stability
system is automatically disabled, the StabiliTrak
®
light will come on and the STABILITRAK OFF
message will appear on the DIC. Both traction
control and StabiliTrak
®are automatically disabled
in this condition.
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Traction Control Operation
The traction control system 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 traction control system is enabled
automatically when you start your vehicle. It will
activate and the StabiliTrak
®light will ash if
it senses that any of the wheels are spinning or
beginning to lose traction while driving. If you turn
off traction control, 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 you allow the wheel(s) of one axle to
spin excessively while the StabiliTrak
®, ABS
and brake warning lights and the SERVICE
STABILITRAK message are displayed, you
could damage the transfer case.The repairs would not be covered by your
warranty. Reduce engine power and do not spin
the wheel(s) excessively while these lights and
this message are displayed.
The traction control system 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, you may notice a reduction in
acceleration, or may hear a noise or vibration.
This is normal.
If your vehicle is in cruise control when the system
activates, the StabiliTrak
®light will ash and the
cruise control will automatically disengage.
When road conditions allow you to use cruise
again, you may re-engage the cruise control.
SeeCruise Control on page 196.
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, you should see your dealer for
service.
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Try to adjust your speed so you can “drive”
through the curve. Maintain a reasonable, steady
speed. Wait to accelerate until you are out of
the curve, and then accelerate gently into
the straightaway.
Adding non-GM accessories can affect your
vehicle’s performance. SeeAccessories and
Modications on page 426.
Steering in Emergencies
There are times when steering can be more
effective than braking. For example, you come over
a hill and nd a truck stopped in your lane, or a car
suddenly pulls out from nowhere, or a child darts
out from between parked cars and stops right in
front of you. You can avoid these problems by
braking — if you can stop in time. But sometimes
you cannot; there is not room. That is the time for
evasive action — steering around the problem.
Your vehicle can perform very well in emergencies
like these. First apply your brakes.
SeeBraking on page 344. It is better to remove as
much speed as you can from a possible collision.
Then steer around the problem, to the left or
right depending on the space available.An emergency like this requires close attention
and a quick decision. If you are holding the
steering wheel at the recommended 9 and 3 o’clock
positions, you can turn it a full 180 degrees very
quickly without removing either hand. But you have
to act fast, steer quickly, and just as quickly
straighten the wheel once you have avoided
the object.
The fact that such emergency situations are
always possible is a good reason to practice
defensive driving at all times and wear safety belts
properly.
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Check your mirrors, glance over your shoulder
and start your left lane change signal before
moving out of the right lane to pass. When you
are far enough ahead of the passed vehicle
to see its front in your inside mirror, activate
your right lane change signal and move
back into the right lane. Remember that if your
passenger side outside mirror is convex, the
vehicle you just passed may seem to be
farther away from you than it really is.
Try not to pass more than one vehicle at a
time on two-lane roads. Reconsider before
passing the next vehicle.
Do not overtake a slowly moving vehicle too
rapidly. Even though the brake lamps are
not ashing, it may be slowing down or starting
to turn.
If you are being passed, make it easy for the
following driver to get ahead of you. Perhaps
you can ease a little to the right.
Loss of Control
Let us review what driving experts say about what
happens when the three control systems — brakes,
steering, and acceleration — do not have enough
friction where the tires meet the road to do what the
driver has asked.
In any emergency, do not give up. Keep trying to
steer and constantly seek an escape route or
area of less danger.
Skidding
In a skid, a driver can lose control of the vehicle.
Defensive drivers avoid most skids by taking
reasonable care suited to existing conditions, and
by not overdriving those conditions. But skids
are always possible.
The three types of skids correspond to your
vehicle’s three control systems. In the braking skid,
your wheels are not rolling. In the steering or
cornering skid, too much speed or steering in a
curve causes tires to slip and lose cornering force.
And in the acceleration skid, too much throttle
causes the driving wheels to spin.
A cornering skid is best handled by easing your
foot off the accelerator pedal.
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Remember: StabiliTrak®helps avoid only the
acceleration skid. SeeStabiliTrak®System
on page 348. If the StabiliTrak®System is off,
then an acceleration skid is also best handled by
easing your foot off the accelerator pedal.
If your vehicle starts to slide, ease your foot off
the accelerator pedal and quickly steer the
way you want the vehicle to go. If you start
steering quickly enough, your vehicle may
straighten out. Always be ready for a second skid
if it occurs.
Of course, traction is reduced when water, snow,
ice, gravel, or other material is on the road.
For safety, you will want to slow down and adjust
your driving to these conditions. It is important
to slow down on slippery surfaces because
stopping distance will be longer and vehicle control
more limited.
While driving on a surface with reduced traction,
try your best to avoid sudden steering,
acceleration, or braking, including reducing vehicle
speed by shifting to a lower gear. Any sudden
changes could cause the tires to slide.You may not realize the surface is slippery until
your vehicle is skidding. Learn to recognize
warning clues — such as enough water, ice, or
packed snow on the road to make a mirrored
surface — and slow down when you have
any doubt.
Remember: Any Anti-Lock Brake System (ABS)
helps avoid only the braking skid.
Off-Road Driving
This off-road guide is for vehicles that have
four-wheel drive or all-wheel drive. Also, see
Braking on page 344. If your vehicle does not have
four-wheel drive or all-wheel drive, you should
not drive off-road unless you are on a level, solid
surface.
Off-road driving can be great fun. But it does have
some denite hazards. The greatest of these is
the terrain itself.
“Off-roading” means you have left the great North
American road system behind. Traffic lanes
are not marked. Curves are not banked. There are
no road signs. Surfaces can be slippery, rough,
uphill or downhill. In short, you have gone
right back to nature.
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