brakes GMC ACADIA 2008 Owner's Manual

Tow/Haul Mode
Your vehicle may have a Tow/Haul mode.
The button to turn it on or
off is located on instrument
panel under the climate
controls.
Push the button to turn it on, push it again to deactivate
the system. You can use this feature to assist when
towing or hauling a heavy load.
When Tow/Haul is activated the Tow/Haul symbol will
come on the instrument panel cluster. SeeTow/Haul
ModeunderTowing a Trailer on page 4-30for
more information.
Automatic Engine Grade Braking
Automatic Engine Grade Braking assists when driving
on a downhill grade. It maintains the vehicle’s speed by
automatically implementing a shift schedule that uses
the engine and the transmission to slow the vehicle. This
reduces wear on the brakes system and increases
control of the vehicle. The system constantly monitors
the vehicle’s speed, acceleration, throttle position,
and whether the brake pedal is being pressed, and
determines when to keep the current vehicle speed or
to slow down. The system will then automatically
command downshifts that reduces the vehicle’s speed,
until the brake pedal is no longer being pressed.
This indicates the desired vehicle speed has been
reached.
While in the Electronic Range Select (ERS) mode,
grade braking is deactivated, allowing the driver to
select a range and limiting the highest gear available.
Grade braking is available for normal driving and in
Tow/Haul mode.
SeeAutomatic Transmission Operation on page 2-30.
2-34

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 5-92.
A trailer was attached to your vehicle, or a bicycle
or an object was hanging out of your liftgate
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.
Rear Vision Camera
Your vehicle may have a Rear Vision Camera system.
Read the entire section before using the system.
The rear vision camera system is designed to help the
driver when backing up. See “Rear Vision Camera”
in the Index of the navigation manual.
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.
2-47

Cruise Control
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.
{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.The cruise control
buttons are located
on left side of the
steering wheel.T(On/Off):Press this button to turn cruise control
on and off. The indicator comes on when cruise control
is on.
+ RES (Resume/Accelerate):Press this button to
make the vehicle accelerate or resume to a previously
set speed.
SET–:Press this button to set the speed or make the
vehicle decelerate.
[(Cancel):Press this button to cancel cruise control.
3-12

Brake System Warning Light
Your vehicle’s hydraulic brake system is divided into
two parts. If one part is not working, the other part can
still work and stop you. For good braking, though,
you need both parts working well.
If the warning light comes on, there is a brake problem.
Have your brake system inspected right away.
This light should come on briey when you turn the
ignition key to ON. If it does not come on then, have it
xed so it will be ready to warn you if there is a problem.
This light may also come on due to low brake uid.
SeeBrakes on page 5-35for more information.When the ignition is on, the brake system warning light
will also come on when you set your parking brake.
The light will stay on if your parking brake does
not release fully. If it stays on after your parking brake
is fully released, it means you have a brake problem.
If the light comes on while you are driving, pull off
the road and stop carefully. Make sure the parking brake
is fully released. You may notice that the pedal is
harder to push or, the pedal 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 4-26.
{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. United StatesCanada
3-47

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.
SeeBrake System Warning Light on page 3-47
For vehicles with a Driver Information Center (DIC),
seeDIC Warnings and Messages on page 3-66for
all brake related DIC messages.
StabiliTrak®Indicator Light
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.
SeeStabiliTrak
®System on page 4-6for more
information.
3-48

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 5-4.
4-3

Braking
SeeBrake System Warning Light on page 3-47.
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 5-4.
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, and
you might even notice that the brake pedal moves
a little. This is normal.
If there is a problem with
ABS, this warning light will
stay on. SeeAntilock
Brake System Warning
Light on page 3-48.
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 wheel.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.
Using ABS
Do not pump the brakes. Just hold the brake pedal
down rmly and let antilock work for you. You might hear
the antilock pump or motor operate, and feel the
brake pedal pulsate, but this is normal.
4-5

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 3-12.
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/retailer for service.
4-8

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 the 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-dealer/non-retailer accessories can affect
your vehicle’s performance. SeeAccessories and
Modifications on page 5-4.
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 the brakes. SeeBraking on
page 4-4. It is better to remove as much speed as youcan 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.
4-10