2008 GMC SIERRA light

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

Release the control when the lower seatback reaches
the desired level of lumbar support.
Your vehicle may have a memory function which allows
seat settings to be saved and recalled. SeeMemory
Seat, Mirrors, and Pedals on page 1-6for more
information.
Keep in mind that as your seating position changes, as
it may during long trips, so should the position of
your lumbar support. Adjust the seat as needed.
Heated Seats
On vehicles with heated front seats, the controls are
located on the driver’s and passenger’s doors.
I(Heated Seatback):Press to turn on the heated
seatback.
J(Heated Seat and Seatback):Press to turn on the
heated seat and seatback.
The light on the button will come on to indicate that the
feature is working. Press the button to cycle through
the temperature settings of high, medium, and low and
to turn the heat to the seat off. Indicator lights will
show the level of heat selected: three for high, two for
medium, and one for low.The heated seats will be canceled ten seconds after the
ignition is turned off. To use the heated seat feature
after restarting your vehicle, press the heated seat
or seatback button again.
Memory Seat, Mirrors, and Pedals
Your vehicle may have the memory package.
The controls for this
feature are located on the
driver’s door panel, and
are used to program
and recall memory settings
for the driver’s seat,
outside mirrors, and the
adjustable throttle and
brake pedal.
To save your positions in memory, do the following:
1. Adjust the driver’s seat, including the seatback
recliner and lumbar, both outside mirrors, and
the throttle and brake pedals to a comfortable
position.
1-6

Lap-Shoulder Belt
All seating positions in your vehicle have a lap-shoulder
belt except for the center front passenger position (if
equipped) if your vehicle is a crew or extended
cab, which has a lap belt. SeeLap Belt (Crew and
Extended Cab) on page 1-34for more information.
Here is how to wear a lap-shoulder belt properly.
1. Adjust the seat, if the seat is adjustable, so you can
sit up straight. To see how, see “Seats” in the Index.
2. Pick up the latch plate and pull the belt across you.
Do not let it get twisted.
The lap-shoulder belt may lock if you pull the belt
across you very quickly. If this happens, let the belt
go back slightly to unlock it. Then pull the belt
across you more slowly.
If you ever pull the shoulder portion of a passenger
belt out all the way, you may engage the child
restraint locking feature. If this happens, just let the
belt go back all the way and start again.
Engaging the child restraint locking feature may
affect the passenger sensing system. See
Passenger Sensing System on page 1-80.3. Push the latch plate into the buckle until it clicks.
Pull up on the latch plate to make sure it is secure.
If the belt is not long enough, seeSafety Belt
Extender on page 1-35.
Make sure the release button on the buckle is
positioned so you would be able to unbuckle the
safety belt quickly if necessary.
4. If equipped with a shoulder belt height adjuster,
move it to the height that is right for you. Improper
shoulder belt height adjustment could reduce
the effectiveness of the safety belt in a crash. See
“Shoulder Belt Height Adjustment” later in this
section.
1-28

{CAUTION:
If the airbag readiness light ever comes on
when you have turned off the airbag, it means
that something may be wrong with the airbag
system. The right front passenger’s airbag
could inate even though the switch is off. If
this ever happens, do not let anyone whom the
national government has identied as a
member of a passenger airbag risk group sit in
the right front passenger’s position (for
example, do not secure a rear-facing child
restraint in the right front passenger’s seat)
until you have your vehicle serviced. See
Airbag Off Switch on page 1-76andAirbag
Readiness Light on page 3-38for more on this,
including important safety information.
If your vehicle does not have a rear seat that will
accommodate a rear-facing child restraint, we
recommend that rear-facing child restraints not be
transported in your vehicle, even if the airbag is off.
If your child restraint has the LATCH system, seeLower
Anchors and Tethers for Children (LATCH) on
page 1-45for how to install your child restraint usingLATCH. If you secure a child restraint using a safety
belt and it uses a top tether, seeLower Anchors
and Tethers for Children (LATCH) on page 1-45for top
tether anchor locations.
Do not secure a child restraint in a position without a
top tether anchor if a national or local law requires that
the top tether be anchored, or if the instructions that
come with the child restraint say that the top strap must
be anchored.
In Canada, the law requires that forward-facing child
restraints have a top tether, and that the tether be
attached.
You will be using the lap-shoulder belt to secure the
child restraint in this position. Follow the instructions that
came with the child restraint.
1. Move the seat as far back as it will go before
securing the forward-facing child restraint.
If you have no other choice but to install a
rear-facing child restraint in this seat, make sure the
airbag is off once the child restraint has been
installed.
When the airbag off switch has turned off the right
front passenger’s frontal airbag, the off indicator
in the airbag off light should light and stay lit when
you start the vehicle. SeeAirbag Off Light on
page 3-39.
2. Put the child restraint on the seat.
1-59

If your vehicle does not have a rear seat that will
accommodate a rear-facing child restraint, we
recommend that rear-facing child restraints not be
transported in your vehicle, even if the airbag is off.
If your child restraint has the LATCH system, seeLower
Anchors and Tethers for Children (LATCH) on
page 1-45for how to install your child restraint using
LATCH. If you secure a child restraint using a safety belt
and it uses a top tether, seeLower Anchors and
Tethers for Children (LATCH) on page 1-45for top
tether anchor locations.
Do not secure a child seat in a position without a top
tether anchor if a national or local law requires that the
top tether be anchored, or if the instructions that
come with the child restraint say that the top strap must
be anchored.
In Canada, the law requires that forward-facing child
restraints have a top tether, and that the tether be
attached.
You will be using the lap-shoulder belt to secure the
child restraint in this position. Follow the instructions that
came with the child restraint.
1. Move the seat as far back as it will go before
securing the forward-facing child restraint.
When the passenger sensing system has turned off
the right front passenger’s frontal airbag, the off
indicator in the passenger airbag status indicatorshould light and stay lit when you start the vehicle.
SeePassenger Airbag Status Indicator on
page 3-41.
2. Put the child restraint on the seat.
3. Pick up the latch plate, and run the lap and shoulder
portions of the vehicle’s safety belt through or
around the restraint. The child restraint instructions
will show you how.
4. Push the latch plate into the buckle until it clicks.
Make sure the release button is positioned so you
would be able to unbuckle the safety belt quickly
if necessary.
1-63

7. If your child restraint manufacturer recommends
using a top tether and the position you are using
has a top tether anchor, attach and tighten the top
tether to the top tether anchor. Refer to the
instructions that came with the child restraint and to
Lower Anchors and Tethers for Children (LATCH)
on page 1-45.
8. Push and pull the child restraint in different
directions to be sure it is secure.
If the airbag is off, the off indicator in the passenger
airbag status indicator will come on and stay on when
the vehicle is started.
If a child restraint has been installed and the on
indicator is lit, turn the vehicle off. Remove the child
restraint from the vehicle and reinstall the child restraint.If, after reinstalling the child restraint and restarting the
vehicle, the on indicator is still lit, check to make
sure that the vehicle’s seatback is not pressing the child
restraint into the seat cushion. If this happens, slightly
recline the vehicle’s seatback and adjust the seat
cushion if possible. Also make sure the child restraint is
not trapped under the vehicle head restraint. If this
happens, adjust the head restraint.
Remove any additional material from the seat such as
blankets, cushions, seat covers, seat heaters or seat
massagers before reinstalling or securing the child
restraint.
If the on indicator is still lit, secure the child in the child
restraint in a rear seat position in the vehicle and
check with your dealer/retailer. If no rear seat is
available, do not install a child restraint in this vehicle
and check with your dealer/retailer.
To remove the child restraint, unbuckle the vehicle’s
safety belt and let it go back all the way. If the top tether
is attached to a top tether anchor, disconnect it.
1-65

{CAUTION:
Airbags inate with great force, faster than the
blink of an eye. Anyone who is up against, or
very close to, any airbag when it inates can
be seriously injured or killed. Do not sit
unnecessarily close to the airbag, as you
would be if you were sitting on the edge of
your seat or leaning forward. Safety belts help
keep you in position before and during a
crash. Always wear your safety belt, even with
airbags. The driver should sit as far back as
possible while still maintaining control of the
vehicle.
Occupants should not lean on or sleep against
the door or side windows in seating positions
with roof-rail airbags.
{CAUTION:
Airbags plus lap-shoulder belts offer the best
protection for adults, but not for young
children and infants. Neither the vehicle’s
safety belt system nor its airbag system is
designed for them. Young children and infants
need the protection that a child restraint
system can provide. Always secure children
properly in your vehicle. To read how, see
Older Children on page 1-35orInfants and
Young Children on page 1-38.
There is an airbag
readiness light on the
instrument panel cluster,
which shows the airbag
symbol.
The system checks the airbag electrical system for
malfunctions. The light tells you if there is an electrical
problem. SeeAirbag Readiness Light on page 3-38
for more information.
1-70

In many crashes severe enough to inate the airbag,
windshields are broken by vehicle deformation.
Additional windshield breakage may also occur from the
right front passenger airbag.
Airbags are designed to inate only once. After an
airbag inates, you will need some new parts for
the airbag system. If you do not get them, the airbag
system will not be there to help protect you in
another crash. A new system will include airbag
modules and possibly other parts. The service
manual for your vehicle covers the need to replace
other parts.
Your vehicle has a crash sensing and diagnostic
module which records information after a crash.
SeeVehicle Data Recording and Privacy on
page 7-16andEvent Data Recorders on page 7-17.
Let only qualied technicians work on the airbag
systems. Improper service can mean that an
airbag system will not work properly. See your
dealer/retailer for service.
Airbag Off Switch
If one of the switches pictured in the following
illustrations is located in your glove box, your vehicle
has an airbag on-off switch that you can use to manually
turn on or off the right front passenger’s airbag. Your
switch may vary slightly.
If your vehicle does not have an airbag off switch, it
may have a passenger sensing system. SeePassenger
Sensing System on page 1-80. United States
Canada
1-76