page 5 GMC ENVOY 2008 Service Manual

Automatic Transmission Operation
There are several different
positions for your gear shift
lever.
PARK (P):This position locks the rear wheels. It is the
best position to use when you start the engine
because your vehicle cannot move easily.{CAUTION:
It is dangerous to get out of your vehicle if the
shift lever is not fully in PARK (P) with the
parking brake rmly set. Your vehicle can roll.
Do not leave your vehicle when the engine is
running unless you have to. If you have left the
engine running, the vehicle can move suddenly.
You or others could be injured. To be sure your
vehicle will not move, even when you are on
fairly level ground, always set your parking
brake and move the shift lever to PARK (P).
SeeShifting Into PARK (P) on page 2-34.Ifyou
are pulling a trailer, seeTowing a Trailer on
page 4-45.
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{CAUTION:
If you have four-wheel drive, your vehicle will
be free to roll — even if your shift lever is
in PARK (P) — if your transfer case is in
NEUTRAL. So, be sure the transfer case is in a
drive gear — not in NEUTRAL. SeeFour-Wheel
Drive on page 2-29. SeeShifting Into PARK (P)
on page 2-34.
Make sure the shift lever is fully in PARK (P) before
starting the engine. Your vehicle has an automatic
transmission shift lock control system. You have to fully
apply the regular brakes rst and then press the shift
lever button before you can shift from PARK (P) when
the ignition key is in ON/RUN. If you cannot shift out of
PARK (P), ease pressure on the shift lever and push the
shift lever all the way into PARK (P) as you maintain
brake application. Then press the shift lever button and
move the shift lever into another gear. SeeShifting Out
of PARK (P) on page 2-36.
REVERSE (R):Use this gear to back up.
Notice:Shifting to REVERSE (R) while your vehicle
is moving forward could damage the transmission.
The repairs would not be covered by your warranty.
Shift to REVERSE (R) only after your vehicle is
stopped.To rock your vehicle back and forth to get out of snow,
ice, or sand without damaging your transmission,
seeIf Your Vehicle is Stuck in Sand, Mud, Ice, or Snow
on page 4-33.
NEUTRAL (N):In this position, the engine does not
connect with the wheels. To restart when you are
already moving, use NEUTRAL (N) only.
{CAUTION:
Shifting into a drive gear while the engine is
running at high speed is dangerous. Unless
your foot is rmly on the brake pedal, your
vehicle could move very rapidly. You could
lose control and hit people or objects. Do not
shift into a drive gear while your engine is
running at high speed.
Notice:Shifting out of PARK (P) or NEUTRAL (N)
with the engine running at high speed may damage
the transmission. The repairs would not be
covered by your warranty. Be sure the engine is not
running at high speed when shifting your vehicle.
2-27

DRIVE (D):This position is for normal driving.
It provides the best fuel economy for your vehicle.
If you need more power for passing, and you are:
Going less than about 35 mph (55 km/h), push the
accelerator pedal about halfway down.
Going about 35 mph (55 km/h) or more, push the
accelerator all the way down.
You will shift down to the next gear and have more
power.
Downshifting the transmission in slippery road conditions
could result in skidding, see “Skidding” underLoss of
Control on page 4-12.
DRIVE (D) can be used when towing a trailer, carrying a
heavy load, driving on steep hills, or for off-road driving.
You may want to shift the transmission to THIRD (3) or,
if necessary, a lower gear selection if the transmission
shifts too often.
THIRD (3):This position is also used for normal driving.
It reduces vehicle speed more than DRIVE (D) without
using your 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.
To shift to the THIRD (3) position, you must rst press
the large button on the shift handle. While the button
is pressed, move the shifter in the THIRD (3) position.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 your brakes off and on.
To shift to the SECOND (2) position, you must rst press
the large button on the shift handle. While the button is
pressed, move the shifter in the SECOND (2) position.
You can also use SECOND (2) for starting the vehicle
from a stop on slippery road surfaces.
FIRST (1):This position reduces vehicle speed even
more than SECOND (2) without using your 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 will not shift
into rst gear until the vehicle is going slowly enough.
To shift to the FIRST (1) position, you must rst press
the large button on the shift handle. While the button is
pressed, move the shifter in the FIRST (1) position.
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.
2-28

AUTO (Automatic Four-Wheel Drive):This setting is
ideal for use when road conditions are variable. When
driving your vehicle in automatic four-wheel drive, the
front axle is engaged, but the vehicle’s power is sent to
the rear wheels. When the vehicle senses a loss of
traction, the system will automatically engage four-wheel
drive. Driving in this mode results in slightly lower fuel
economy than Two-Wheel High.
4
m(Four-Wheel High):This setting should be used
when you need extra traction, such as on snowy or
icy roads or in most off-road situations. This setting also
engages your front axle to help drive your vehicle.
4
n(Four-Wheel Low):This setting also engages
your front axle and delivers extra torque. It sends
maximum power to all four wheels. You might choose
this setting if you are driving off-road in deep sand,
deep mud, and climbing or descending steep hills.
{CAUTION:
Shifting the transfer case to NEUTRAL
can cause your vehicle to roll even if the
transmission is in PARK (P). You or someone
else could be seriously injured. Be sure to set
the parking brake before placing the transfer
case in NEUTRAL. SeeParking Brake on
page 2-33.
NEUTRAL:Shift the vehicle’s transfer case
to NEUTRAL only when towing your vehicle.
SeeRecreational Vehicle Towing on page 4-40
for more information.
An indicator light in the knob will show you which
position the transfer case is in. The indicator lights will
come on briey when you turn on the ignition and one will
stay on. If the lights do not come on, you should take your
vehicle to your dealer for service. An indicator light will
ash while shifting the transfer case. It will stay on when
the shift is complete. If for some reason the transfer case
cannot make a requested shift, it will return to the last
chosen setting.
If the service Four-Wheel Drive Warning Light on the
instrument panel cluster stays on, you should take
your vehicle to your dealer for service. SeeService
Four-Wheel Drive Warning Light on page 3-47for
further information.
2-30

Parking Brake
To set the parking brake,
hold the regular brake
pedal down with your
foot and pull up on
the parking brake lever
located between the seats.
To release the parking brake, hold the regular brake
pedal down. Pull the parking brake lever up until you
can press in the button at the end of the lever. Hold the
button in as you move the parking brake lever all the
way down.If the ignition is on, the brake system warning light on
the instrument panel cluster will come on. SeeBrake
System Warning Light on page 3-38.
Notice:Driving with the parking brake on can
overheat the brake system and cause premature
wear or damage to brake system parts. Verify that
the parking brake is fully released and the brake
warning light is off before driving.
If you are towing a trailer and you must park on a hill,
seeTowing a Trailer on page 4-45.
2-33

Shifting Into PARK (P)
{CAUTION:
It can be dangerous to get out of your vehicle
if the shift lever is not fully in PARK (P) with the
parking brake rmly set. Your vehicle can roll.
If you have left the engine running, the vehicle
can move suddenly. You or others could be
injured. To be sure your vehicle will not move,
even when you are on fairly level ground, use
the steps that follow. With four-wheel drive,
your vehicle will be free to roll — even if your
shift lever is in PARK (P) — if your transfer case
is in NEUTRAL. So, be sure the transfer case
is in a drive gear — not in NEUTRAL. See
Four-Wheel Drive on page 2-29. Always put the
shift lever fully in PARK (P) with the parking
brake rmly set. If you are pulling a trailer,
seeTowing a Trailer on page 4-45.To shift into PARK (P):
1. Hold the brake pedal down with your foot and set
the parking brake.
2. Move the shift lever into PARK (P) by pressing the
button on the side of the shift lever and pushing the
lever all the way toward the front of the vehicle.
3. Turn the ignition key to OFF/LOCK.
4. Remove the key and take it with you. You know
your vehicle is in PARK (P) if the key can be
removed from the ignition.
2-34

Leaving Your Vehicle With the Engine
Running
{CAUTION:
It can be dangerous to leave your vehicle with
the engine running. Your vehicle could move
suddenly if the shift lever is not fully in
PARK (P) with the parking brake rmly set.
If you have four-wheel drive, your vehicle will be
free to roll – even if your lever is in PARK (P) – if
your transfer case is in NEUTRAL. So be sure
the transfer case is in a drive gear – not
NEUTRAL. SeeFour-Wheel Drive on page 2-29.
And, if you leave the vehicle with the engine
running, it could overheat and even catch re.
You or others could be injured. Do not leave
your vehicle with the engine running unless
you have to.If you have to leave your vehicle with the engine
running, be sure your vehicle is in PARK (P) and your
parking brake is rmly set before you leave it. After you
have moved the shift lever into PARK (P), hold the
regular brake pedal down. Then, see if you can move
the shift lever away from PARK (P) without rst pressing
the button on the console shift lever. If you can, it
means that the shift lever was not fully locked into
PARK (P).
Torque Lock
If you are parking on a hill and you do not shift your
transmission into PARK (P) properly, the weight of the
vehicle may put too much force on the parking pawl
in the transmission. You may nd it difficult to pull
the shift lever out of PARK (P). This is called “torque
lock.” To prevent torque lock, set the parking brake
and then shift into PARK (P) properly before you leave
the driver’s seat. To nd out how, seeShifting Into
PARK (P) on page 2-34.
When you are ready to drive, move the shift lever out of
PARK (P) before you release the parking brake.
If torque lock does occur, you may need to have another
vehicle push yours a little uphill to take some of the
pressure from the parking pawl in the transmission,
so you can pull the shift lever out of PARK (P).
2-35

Shifting Out of PARK (P)
This vehicle has an electronic shift lock release system.
The shift lock release is designed to:
Prevent ignition key removal unless the shift lever
is in PARK (P) with the shift lever button fully
released, and
Prevent movement of the shift lever out of
PARK (P), unless the ignition is in ON/RUN
and the regular brake pedal is applied.
The shift lock release is always functional except in the
case of an uncharged or low voltage (less than 9 volt)
battery.If your vehicle has an uncharged battery or a battery
with low voltage, try charging or jump starting the
battery. SeeJump Starting on page 5-42for more
information.
To shift out of PARK (P) use the following:
1. Apply the brake pedal.
2. Press the shift lever button.
3. Move the shift lever to the desired position.
If you still are unable to shift out of PARK (P):
1. Fully release the shift lever button.
2. Hold the brake pedal down and press the shift lever
button again.
3. Move the shift lever to the desired position.
If you still cannot move the shift lever from PARK (P),
consult your dealer/retailer or a professional towing
service.
2-36

Running the Vehicle While Parked
It is better not to park with the engine running. But if you
ever have to, here are some things to know.
{CAUTION:
Idling the engine with the climate control
system off could allow dangerous exhaust into
your vehicle. See the earlier caution under
Engine Exhaust on page 2-37.
Also, idling in a closed-in place can let deadly
carbon monoxide (CO) into your vehicle even if
the climate control fan is at the highest setting.
One place this can happen is a garage.
Exhaust — with CO — can come in easily.
NEVER park in a garage with the engine
running.
Another closed-in place can be a blizzard.
SeeWinter Driving on page 4-30.
{CAUTION:
It can be dangerous to get out of your vehicle
if the shift lever is not fully in PARK (P) with
the parking brake rmly set. Your vehicle can
roll. Do not leave your vehicle when the engine
is running unless you have to. If you have left
the engine running, the vehicle can move
suddenly. You or others could be injured.
To be sure your vehicle will not move, even
when you are on fairly level ground, always set
the parking brake and move the shift lever to
PARK (P).
2-38

{CAUTION:
If your vehicle has four-wheel drive, it will
be free to roll — even if the shift lever is in
PARK (P) — if the transfer case is in
NEUTRAL. So be sure the transfer case
is in a drive gear — not in NEUTRAL.
SeeFour-Wheel Drive on page 2-29.
Follow the proper steps to be sure your vehicle will not
move. SeeShifting Into PARK (P) on page 2-34.
If you are pulling a trailer, seeTowing a Trailer on
page 4-45.
Mirrors
Manual Rearview Mirror
When you are sitting in a comfortable driving position,
adjust the mirror so you can see clearly behind your
vehicle. Grip the mirror in the center to move it up
or down and side to side. The day/night adjustment
allows you to adjust the mirror to avoid glare from the
lamps behind you. Move the lever to the right for
nighttime use and to the left for daytime use.
Manual Rearview Mirror with
OnStar
®
When you are sitting in a comfortable driving position,
adjust the mirror so you can see clearly behind your
vehicle. Hold the mirror in the center to move it up or
down and side to side. The day/night adjustment allows
you to adjust the mirror to avoid glare from the lamps
behind you. Move the lever to the right for nighttime
use and to the left for daytime use.
There may also be three OnStar
®buttons located at the
bottom of the mirror face. See your dealer/retailer for
more information on the system and how to subscribe to
OnStar
®. SeeOnStar®System on page 2-48for more
information on the services OnStar®provides.
Automatic Dimming Rearview Mirror
with OnStar
®and Compass
Your vehicle may have an automatic-dimming rearview
mirror with a compass.
There may be three additional buttons for the OnStar
®
system. See your dealer/retailer for more information
on the system and how to subscribe to OnStar®.
SeeOnStar®System on page 2-48for more information
about the services OnStar®provides.
O(On/Off):This is the on/off button.
2-39