brakes GMC YUKON 2008 Owner's Manual

MANUAL MODE (M):This position, is available on
vehicles with the Allison Transmission®or Hydra-Matic®
6-Speed transmission. It lets drivers select the range
of gears appropriate for current driving conditions. If your
vehicle has this feature, see Range Select Mode
(Allison Transmission
®or Hydra-Matic®6-Speed
transmission) later in this section.
THIRD (3):This position is also used for normal driving.
It reduces vehicle speed more than DRIVE (D) without
using the brakes. You might choose THIRD (3)
instead of DRIVE (D) when driving on hilly, winding
roads, when towing a trailer, so there is less shifting
between gears and when going down a steep hill.
SECOND (2):This position reduces vehicle speed even
more than THIRD (3) without using your brakes. You can
use SECOND (2) on hills. It can help control your speed
as you go down steep mountain roads, but then you
would also want to use the brakes off and on.
If you manually select SECOND (2) in an automatic
transmission, the transmission will start in second gear.
You can use this feature for reducing the speed of the
rear wheels when you are trying to start your vehicle from
a stop on slippery road surfaces.FIRST (1):For the Hydra-Matic
®4-Speed transmission
this position reduces vehicle speed even more than
SECOND (2) without using the brakes. You can use it
on very steep hills, or in deep snow or mud. If the
shift lever is put in FIRST (1) while the vehicle is moving
forward, the transmission does not shift into rst gear
until the vehicle is going slowly enough.
For an Allison Transmission
®or Hydra-Matic®6-Speed
transmission, this position reduces vehicle speed
without using your brakes. You can use it for
major/severe downgrades and off-road driving where
the vehicle would otherwise accelerate due to steepness
of grade. When you shift to FIRST (1) it provides the
lowest gear appropriate to your current road speed and
continues to downshift as the vehicle slows, eventually
downshifting to FIRST (1) gear.
Notice:Spinning the tires or holding the vehicle in
one place on a hill using only the accelerator
pedal may damage the transmission. The repair will
not be covered by your warranty. If you are stuck,
do not spin the tires. When stopping on a hill,
use the brakes to hold the vehicle in place.
2-35

Range Selection Mode (Allison®or
Hydra-Matic®6-Speed Transmission)
Your vehicle may have a Range Selection Mode.
The Range Selection Mode helps control the vehicle’s
transmission and vehicle speed while driving down hill
or towing a trailer by letting you select a desired range
of gears.
To use this feature, do the following:
1. Move the shift lever to the MANUAL MODE (M).
2. Press the plus/minus buttons, located on the
steering column shift lever, to select the desired
range of gears for your current driving conditions.When MANUAL MODE (M) is selected a number
displays next to the M, indicating the current gear.
This number is the highest gear that can be used.
However, your vehicle can automatically shift to lower
gears as it adjusts to driving conditions. This means that
all gears below that number are available. When
FIFTH (5) is selected, FIRST (1) through FIFTH (5)
gears are automatically shifted by the vehicle, but
SIXTH (6) cannot be used until the plus/minus button
located on the steering column lever is used to change
to the gear.
Grade Braking is not available when the Range
Selection Mode is active. SeeTow/Haul Mode on
page 2-37.
While using the Range Selection mode feature, cruise
control and the Tow/Haul mode can be used.
Notice:Spinning the tires or holding the vehicle in
one place on a hill using only the accelerator
pedal may damage the transmission. The repair will
not be covered by your warranty. If you are stuck,
do not spin the tires. When stopping on a hill,
use the brakes to hold the vehicle in place.
2-36

When the System Does Not Seem to
Work Properly
The driver disables the system.
The parking brake pedal is depressed.
The ultrasonic sensors are not clean. Keep your
vehicle’s rear bumper free of mud, dirt, snow,
ice and slush. For cleaning instructions, see
Washing Your Vehicle on page 5-111.
A trailer was attached to your vehicle, or a bicycle
or an object was hanging out of your liftgate/liftglass
during your last drive cycle, the red light may
illuminate in the rear display. Once the attached
object is removed, URPA will return to normal
operation.
A tow bar is attached to your vehicle.
The vehicle’s bumper is damaged. Take the vehicle
to your dealer/retailer to repair the system.
Other conditions may affect system performance,
such as vibrations from a jackhammer or the
compression of air brakes on a very large truck.
If the system is still disabled, after driving forward at
least 15 mph (25 km/h), take your vehicle to your
dealer/retailer.
OnStar®System
OnStar uses several innovative technologies and live
advisors to provide you with a wide range of safety,
security, information, and convenience services. If your
airbags deploy, the system is designed to make an
automatic call to OnStar Emergency advisors who can
request emergency services be sent to your location.
If you lock your keys in the vehicle, call OnStar at
1-888-4-ONSTAR and they can send a signal to unlock
your doors. If you need roadside assistance, press
the OnStar button and they can contact Roadside
Service for you.
OnStar service is provided to you subject to the
OnStar Terms and Conditions. You may cancel your
OnStar service at any time by contacting OnStar.
2-60

Cruise Control
{CAUTION:
Cruise control can be dangerous where you
cannot drive safely at a steady speed. So, do
not use your cruise control on winding roads
or in heavy traffic.
Cruise control can be dangerous on slippery
roads. On such roads, fast changes in tire
traction can cause excessive wheel slip, and
you could lose control. Do not use cruise
control on slippery roads.With cruise control, you can maintain a speed of about
25 mph (40 km/h) or more without keeping your foot
on the accelerator. This can really help on long
trips. Cruise control does not work at speeds below
about 25 mph (40 km/h).
When you apply your brakes, cruise control is
turned off.
If your vehicle has the StabiliTrak
®system and begins
to limit wheel spin while you are using cruise control, the
cruise control will automatically disengage. See
StabiliTrak
®System on page 4-6. When road conditions
allow you to safely use it again, you may turn the
cruise control back on.
3-13

If the warning light comes on and a chime sounds there
could be a brake problem. Have your brake system
inspected right away.
This light may also come on due to low brake uid. See
Brakes on page 5-41for more information.
This light should come on briey when you turn the
ignition key to RUN. If it does not come on then, have it
xed so it will be ready to warn you if there is a
problem.
{CAUTION:
Your brake system may not be working
properly if the brake system warning light is
on. Driving with the brake system warning light
on can lead to an accident. If the light is still
on after you have pulled off the road and
stopped carefully, have the vehicle towed for
service.
If the light comes on while you are driving, pull off the
road and stop carefully. You may notice that the pedal is
harder to push or may go closer to the oor. It may
take longer to stop. If the light is still on, have the vehicle
towed for service. SeeTowing Your Vehicle on
page 4-45. United States
Canada
3-45

Antilock Brake System
Warning Light
For vehicles with the
Antilock Brake System
(ABS), this light will come
on briey when you
start the engine.
That is normal. If the light does not come on then, have it
xed so it will be ready to warn you if there is a problem.
If the ABS light stays on, turn the ignition off, if the light
comes on when you are driving, stop as soon as it
is safely possible and turn the ignition off. Then start the
engine again to reset the system. If the ABS light still
stays on, or comes on again while you are driving, your
vehicle needs service. If the regular brake system
warning light is not on, you still have brakes, but you do
not have antilock brakes. If the regular brake system
warning light is also on, you do not have antilock brakes
and there is a problem with your regular brakes. See
Brake System Warning Light on page 3-44
For vehicles with a Driver Information Center (DIC), see
DIC Warnings and Messages on page 3-64for all
brake related DIC messages.
StabiliTrak®Indicator Light
If equipped, this warning
light should come on
briey when the engine is
started.
If the warning light does not come on then, have it xed
so it will be ready to warn you if there is a problem. If
it stays on, or comes on when you are driving, there may
be a problem with your StabiliTrak
®system and your
vehicle may need service. When this warning light is on,
the system is off and will not limit wheel spin. Adjust
your driving accordingly.
This light will also ash when the StabiliTrak
®system is
active.
If the StabiliTrak
®system warning light comes on and
stays on for an extended period of time when the system
is turned on, your vehicle needs service. See
StabiliTrak
®System on page 4-6for more information.
3-46

SERVICE AIR BAG
This message displays if there is a problem with the
airbag system. Have your dealer/retailer inspect
the system for problems. SeeAirbag Readiness Light
on page 3-40andAirbag System on page 1-76for more
information.
SERVICE BATTERY CHARGING
SYSTEM
On some vehicles, this message displays if there is a
problem with the battery charging system. Under certain
conditions, the charging system light may also turn
on in the instrument panel cluster. SeeCharging System
Light on page 3-43. Driving with this problem could
drain the battery. Turn off all unnecessary accessories.
Have the electrical system checked as soon as
possible. See your dealer/retailer.
SERVICE BRAKE SYSTEM
This message displays along with the brake system
warning light if there is a problem with the brake system.
SeeBrake System Warning Light on page 3-44. If this
message appears, stop as soon as possible and turn off
the vehicle. Restart the vehicle and check for the
message on the DIC display. If the message is still
displayed or appears again when you begin driving, the
brake system needs service as soon as possible.
See your dealer/retailer.
SERVICE BRAKES SOON
This message displays if there is a problem with the
brake system. If this message appears, stop as soon as
possible and turn off the vehicle. Restart the vehicle
and check for the message on the DIC display. If
the message is still displayed or appears again when
you begin driving, the brake system needs service. See
your dealer/retailer.
SERVICE PARK ASSIST
If your vehicle has the Ultrasonic Rear Parking Assist
(URPA) system, this message displays if there is a
problem with the URPA system. Do not use this system
to help you park. SeeUltrasonic Rear Parking Assist
(URPA) on page 2-58for more information. See
your dealer/retailer for service.
SERVICE STABILITRAK
If your vehicle has StabiliTrak®and this message
displays, it means there may be a problem with the
StabiliTrak
®system. If you see this message, try to reset
the system. Stop; turn off the engine for at least
15 seconds; then start the engine again. If this message
still comes on, it means there is a problem. You
should see your dealer/retailer for service. The vehicle
is safe to drive, however, you do not have the benet
of StabiliTrak
®, so reduce your speed and drive
accordingly.
3-69

Death and injury associated with drinking and driving is
a global tragedy.
Alcohol affects four things that anyone needs to drive a
vehicle: judgment, muscular coordination, vision, and
attentiveness.
Police records show that almost 40 percent of all motor
vehicle-related deaths involve alcohol. In most cases,
these deaths are the result of someone who was
drinking and driving. In recent years, more than
17,000 annual motor vehicle-related deaths have been
associated with the use of alcohol, with about
250,000 people injured.
For persons under 21, it is against the law in every
U.S. state to drink alcohol. There are good medical,
psychological, and developmental reasons for
these laws.
The obvious way to eliminate the leading highway
safety problem is for people never to drink alcohol and
then drive.Medical research shows that alcohol in a person’s
system can make crash injuries worse, especially
injuries to the brain, spinal cord, or heart. This means
that when anyone who has been drinking — driver
or passenger — is in a crash, that person’s chance of
being killed or permanently disabled is higher than if the
person had not been drinking.
Control of a Vehicle
The following three systems help to control your vehicle
while driving — brakes, steering, and accelerator. At
times, as when driving on snow or ice, it is easy to ask
more of those control systems than the tires and
road can provide. Meaning, you can lose control of your
vehicle. SeeStabiliTrak
®System on page 4-6.
Adding non-dealer/non-retailer accessories can affect
your vehicle’s performance. SeeAccessories and
Modifications on page 5-3.
4-3

Braking
If your vehicle is a Two-mode Hybrid, see the Two-mode
Hybrid manual for more information.
SeeBrake System Warning Light on page 3-44.
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 the 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. The brakes might not have time to cool
between hard stops. The 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 vehicle’s engine ever stops while you are driving,
brake normally but do not pump the brakes. If you do,
the pedal could get harder to push down. If the
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 can take longer to stop and
the brake pedal will be harder to push.
Adding non-dealer/non-retailer accessories can affect
your vehicle’s performance. SeeAccessories and
Modifications on page 5-3.
4-4

Antilock Brake System (ABS)
Your vehicle has the Antilock Brake System (ABS), an
advanced electronic braking system that will help
prevent a braking skid.
When you start the engine and begin to drive away,
ABS will check itself. You might 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. SeeAntilock
Brake System Warning
Light on page 3-46.
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 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/retailer for
service.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, the 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 the brakes if
that vehicle suddenly slows or stops. Always leave
enough room up ahead to stop, even though you
have ABS.
4-5