2007 GMC YUKON brakes

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.
Adding non-GM accessories can affect your
vehicle’s performance. SeeAccessories and
Modications on page 421.
Braking
SeeBrake System Warning Light on page 233.
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.
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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. 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 421.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 234.
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.
As you brake, your computer keeps receiving
updates on wheel speed and controls braking
pressure accordingly.
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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 Differential
If your vehicle has this feature, your locking
differential 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 wheels
has no traction and the other does, this feature will
allow the wheel with traction to move the vehicle.
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.
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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. See
Cruise Control on page 200.
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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Suppose you are steering through a sharp curve.
Then you suddenly accelerate. Both control
systems — steering and acceleration — have to
do their work where the tires meet the road.
Adding the sudden acceleration can demand too
much of those places. You can lose control.
What should you do if this ever happens? Ease up
on the accelerator pedal, steer the vehicle the
way you want it to go, and slow down.
Speed limit signs near curves warn that you
should adjust your speed. Of course, the posted
speeds are based on good weather and road
conditions. Under less favorable conditions you will
want to go slower.
If you need to reduce your speed as you approach
a curve, do it before you enter the curve, while
your front wheels are straight ahead.
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 421.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 346. 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.
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If other vehicles are lined up to pass a slow
vehicle, wait your turn. But take care that
someone is not trying to pass you as you pull
out to pass the slow vehicle. Remember to
glance over your shoulder and check the
blind spot.
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.
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If you decide you can go down a hill safely, then
try to keep your vehicle headed straight down, and
use a low gear. This way, engine drag can help
the brakes and they will not have to do all
the work. Descend slowly, keeping your vehicle
under control at all times.
{CAUTION:
Heavy braking when going down a hill can
cause your brakes to overheat and fade.
This could cause loss of control and a
serious accident. Apply the brakes lightly
when descending a hill and use a low
gear to keep vehicle speed under control.
Q:Are there some things I should not do
when driving down a hill?
A:Yes! These are important because if you
ignore them you could lose control and
have a serious accident.
When driving downhill, avoid turns that take
you across the incline of the hill. A hill that
is not too steep to drive down may be
too steep to drive across. You could roll over
if you do not drive straight down.
Never go downhill with the transmission in
NEUTRAL (N). This is called “free-wheeling.”
The brakes will have to do all the work
and could overheat and fade.
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