2008 GMC SIERRA four wheel drive

Seats and Restraint Systems........................... 1-1
Front Seats
............................................... 1-3
Rear Seats
..............................................1-12
Safety Belts
.............................................1-14
Child Restraints
.......................................1-35
Airbag System
.........................................1-68
Restraint System Check
............................1-87
Features and Controls..................................... 2-1
Keys
........................................................ 2-3
Doors and Locks
......................................2-10
Windows
.................................................2-15
Theft-Deterrent Systems
............................2-18
Starting and Operating Your Vehicle
...........2-22
Mirrors
....................................................2-55
Object Detection Systems
..........................2-63
OnStar
®System
......................................2-65
Universal Home Remote System
................2-68
Storage Areas
.........................................2-74
Sunroof
..................................................2-79
Instrument Panel............................................. 3-1
Instrument Panel Overview
.......................... 3-4
Climate Controls
......................................3-25
Warning Lights, Gages, and Indicators
........3-34
Driver Information Center (DIC)
..................3-54
Audio System(s)
.......................................3-80Driving Your Vehicle....................................... 4-1
Your Driving, the Road, and Your Vehicle
..... 4-2
Towing
...................................................4-50
Service and Appearance Care.......................... 5-1
Service
..................................................... 5-4
Fuel
......................................................... 5-6
Checking Things Under the Hood
...............5-12
Rear Axle
...............................................5-51
Four-Wheel Drive
.....................................5-52
Front Axle
...............................................5-54
Noise Control System
...............................5-56
Headlamp Aiming
.....................................5-56
Bulb Replacement
....................................5-59
Windshield Wiper Blade Replacement
.........5-65
Tires
......................................................5-66
Appearance Care
...................................5-112
Vehicle Identication
...............................5-121
Electrical System
....................................5-122
Capacities and Specications
...................5-130
Maintenance Schedule..................................... 6-1
Maintenance Schedule
................................ 6-2
Customer Assistance Information.................... 7-1
Customer Assistance and Information
........... 7-2
Reporting Safety Defects
...........................7-14
Vehicle Data Recording and Privacy
...........7-16
Index................................................................ 1
2008 GMC Sierra Owner ManualM

Keys...............................................................2-3
Remote Keyless Entry (RKE) System................2-4
Remote Keyless Entry (RKE) System
Operation...................................................2-5
Remote Vehicle Start......................................2-7
Doors and Locks............................................2-10
Door Locks..................................................2-10
Power Door Locks........................................2-10
Delayed Locking...........................................2-10
Programmable Automatic Door Locks..............2-11
Rear Door Security Locks..............................2-11
Lockout Protection........................................2-12
Rear Doors..................................................2-13
Tailgate.......................................................2-14
Windows........................................................2-15
Manual Windows..........................................2-16
Power Windows............................................2-16
Power Sliding Rear Window...........................2-17
Sun Visors...................................................2-18
Theft-Deterrent Systems..................................2-18
Content Theft-Deterrent.................................2-18
PASS-Key
®III+............................................2-20
PASS-Key®III+ Operation..............................2-20
Starting and Operating Your Vehicle................2-22
New Vehicle Break-In....................................2-22
Ignition Positions..........................................2-22Retained Accessory Power (RAP)...................2-23
Starting the Engine.......................................2-24
Fast Idle System..........................................2-25
Adjustable Throttle and Brake Pedal................2-26
Engine Coolant Heater..................................2-26
Active Fuel Management™.............................2-27
Automatic Transmission Operation...................2-28
Tow/Haul Mode............................................2-34
Four-Wheel Drive..........................................2-36
Parking Brake..............................................2-49
Shifting Into PARK (P)...................................2-50
Shifting Out of PARK (P)...............................2-52
Parking Over Things That Burn.......................2-53
Engine Exhaust............................................2-53
Running the Engine While Parked...................2-54
Mirrors...........................................................2-55
Manual Rearview Mirror.................................2-55
Automatic Dimming Rearview Mirror with
OnStar
®, Compass and Temperature
Display....................................................2-55
Automatic Dimming Rearview Mirror with
Compass and Temperature Display..............2-57
Outside Manual Mirrors..................................2-58
Outside Trailer-Tow Mirrors............................2-59
Outside Power Mirrors...................................2-59
Outside Power Foldaway Mirrors.....................2-61
Section 2 Features and Controls
2-1

{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 2-50. If you are pulling a trailer, see
Towing a Trailer on page 4-55.
{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, Two-Wheel Drive High or
Four-Wheel Drive High or Four-Wheel Drive
Low — not in NEUTRAL. SeeShifting Into
PARK (P) on page 2-50.
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 4-34.
2-29

Using this information, it detects when the truck is on a
downhill grade and the driver desires to slow the
vehicle by pressing the brake. See the diesel
supplement for information on Cruise Grade Braking.
Also seeTowing a Trailer on page 4-55for more
information.
Four-Wheel Drive
If your vehicle has Four-Wheel Drive, you can send the
engine’s driving power to all four wheels for extra
traction. To get the most satisfaction out of Four-Wheel
Drive, you must be familiar with its operation. Read
the part that follows before using Four-Wheel Drive. See
the appropriate text for the transfer case in your
vehicle.
Notice:Driving on clean, dry pavement in
Four-Wheel-Drive High or Four-Wheel-Drive Low for
an extended period of time may cause premature
wear on your vehicle’s powertrain. Do not drive on
clean, dry pavement in Four-Wheel-Drive High or
Four-Wheel-Drive Low for extended periods of time.
While driving on clean dry pavement and during tight
turns, you may experience vibration in the steering
system.
Front Axle Locking Feature
The front axle locks and unlocks automatically when
you shift the transfer case. Some delay for the axle to
lock or unlock is normal.
Manual Transfer Case
The transfer case shift lever is on the oor to the right
of the driver. Use this lever to shift into and out of
Four-Wheel Drive.
2-36

A Four-Wheel Drive
indicator light comes on
when you shift into
four-wheel drive and the
front axle engages.
SeeFour-Wheel-Drive
Light on page 3-53
Some delay between shifting and when the indicator
light comes on is normal.
Recommended Transfer Case Settings
Driving ConditionsTransfer Case Settings
2m4m4nN
Normal YES
Severe YES
Extreme YES
Vehicle in Tow* YES
*SeeRecreational Vehicle Towing on page 4-50
Towing Your Vehicle on page 4-50Notice:Driving on clean, dry pavement in
four-wheel drive for an extended period of time can
cause premature wear on your vehicle’s powertrain.
Do not drive on clean, dry pavement in Four-Wheel
Drive for extended periods of time.
4
n(Four-Wheel-Drive Low):This setting also
engages the front axle and delivers extra torque. You
may never need Four-Wheel-Drive Low. It sends
maximum power to all four wheels. You might choose
Four-Wheel-Drive Low if you are driving off-road in deep
sand, deep mud, deep snow, and while climbing or
descending steep hills. When operating in Four-Wheel
Low, the gear ratio provides additional torque when
compared to Four-Wheel-Drive High. The transmission
gear shift feel is exaggerated.
2-37

A parking brake symbol
is located next to the
N (NEUTRAL) symbol
as a reminder to set the
parking brake before
shifting the transfer
case in Neutral.
{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 2-49.N (NEUTRAL):Shift to this setting only when your
vehicle needs to be towed. SeeRecreational Vehicle
Towing on page 4-50orTowing Your Vehicle on
page 4-50.
2
m(Two-Wheel-Drive High):This setting is used for
driving in most street and highway situations. The
front axle is not engaged in two-wheel drive. This setting
also provides the best fuel economy.
4
m(Four-Wheel-Drive High):Use this setting when
you need extra traction, such as on snowy or icy
roads or in most off-road situations. This setting also
engages the front axle to help drive your vehicle. This is
the best setting to use when plowing snow.
You can shift from Two-Wheel-Drive High to
Four-Wheel-Drive High or Four-Wheel-Drive High to
Two-Wheel-Drive High while the vehicle is moving. In
extremely cold weather, it may be necessary to stop or
slow the vehicle to shift into Four-Wheel-Drive High.
2-38

When Using the Manual Transfer Case

Shifting should be made using quick motions.
Shifting slowly may make it more difficult to shift.
You may notice that it is harder to shift when the
vehicle is cold. After the vehicle warms up the
shifting will return to normal.
While in Four-Wheel High or Four-Wheel-Drive Low
you may experience reduced fuel economy.
Avoid driving in Four-Wheel Drive on clean, dry
pavement. It may cause your tires to wear faster,
and make the transfer case harder to shift and run
noisier.
If the transfer case shifter is in the NEUTRAL
position and you have difficulty reaching the
selected transfer case mode, with the engine
running, shift the transmission momentarily to drive
and then back to NEUTRAL. This will realign the
gear teeth in the transfer case and allow you
to complete the shift.
Shifting from Two-Wheel-Drive High to
Four-Wheel-Drive High

Shifts between Two-Wheel-Drive High and
Four-Wheel-Drive High can be made at any
vehicle speed.
Shift the transfer case lever in one continuous
motion into either the Four-Wheel-Drive High
or Two-Wheel-Drive High position.
In extremely cold weather, it may be necessary
to slow or stop the vehicle to shift into
Four-wheel-Drive High until your vehicle has
warmed up.
While in Four-Wheel-Drive High, your vehicle can
be driven at any posted legal speed limit.
2-39

Shifting In or Out of Four-Wheel-Drive Low
Notice:Shifting the transfer case into
Four-Wheel-Drive Low while moving at speeds
faster than 3 mph (5 km/h) may cause premature
wear to the transfer case, and may cause the gears
to grind. To avoid causing premature wear, and
grinding the gears, do not shift the transfer case into
Four-Wheel-Drive Low while the vehicle is moving
faster than 3 mph (5 km/h).
Shifting into Four-Wheel-Drive Low should be done, if
possible, with the vehicle at a slight roll, 3 mph (5 km/h)
or less.
Shift the transmission into NEUTRAL (N).
{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 2-49.
Shifting into Four-Wheel-Drive Low with the vehicle
at a stop may be more difficult. You may be unable
to complete the shift to Four-Wheel-Drive Low,
and will end up in NEUTRAL. This is normal, and is
a function of the gear teeth aligning in your
transfer case. When this happens, make sure the
engine is on, shift your transmission momentarily to
drive and back to NEUTRAL, and then complete
the shift.
Shift the transfer case shift lever in one continuous
motion into the Four-Wheel-Drive Low position.
When Four-Wheel-Drive Low do not drive faster
than 45 mph. This will reduce wear and extend
the life of your transfer case.
Shifting In or Out of NEUTRAL
1. With the vehicle running and the engine at an idle
set the parking brake.
2. Place the transmission into NEUTRAL (N).
Shift the transfer case in one continuous motion into or
out of the NEUTRAL position.
2-40