2008 GMC SIERRA tow

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

Center Seat
Your vehicle may have a front center seat. The seatback
doubles as an armrest and cupholder/storage area for
the driver and passenger when the center seat is
not used. Do not use it as a seating position when the
seatback is folded down.
Rear Seats
Rear Seat Operation (Full Bench)
Folding the Rear Seat
To fold the seat up, do the following:
Notice:Folding a rear seat with the safety belts
still fastened may cause damage to the seat or the
safety belts. Always unbuckle the safety belts
and return them to their normal stowed position
before folding a rear seat.1. Pull up on the front of
the seat cushion while
pulling down on the
release strap, located
under the seat
cushion.
2. Pull the seat cushion up until it latches with the
seatback.
3. After latching the seat cushion up, pull forward on it
to make sure it is locked.
To fold the seat down, do the following:
1. Push the seat cushion rearward while pulling the
release strap, located under the seat cushion. Pull
the seat cushion down until it latches.
2. After latching the seat cushion, pull up on it to
make sure it is locked.
1-12

Rear Seat Operation (Split Bench)
Folding Rear Seat
On a vehicle with a second row 60/40 split seat
either side of the rear seat may be folded for added
cargo space.
Notice:Folding a rear seat with the safety belts
still fastened may cause damage to the seat or the
safety belts. Always unbuckle the safety belts
and return them to their normal stowed position
before folding a rear seat.
Make sure that nothing is on the seat.
To fold the seat, slowly pull the seat cushion up.
To return the seat to the normal seating position, slowly
pull the seat cushion down.
{CAUTION:
A safety belt that is improperly routed, not
properly attached, or twisted will not provide
the protection needed in a crash. The person
wearing the belt could be seriously injured.
After raising the rear seatback, always check
to be sure that the safety belts are properly
routed and attached, and are not twisted.
1-13

{CAUTION:
Children can be seriously injured or strangled
if a shoulder belt is wrapped around their neck
and the safety belt continues to tighten.
Secure any unused safety belts behind the
child restraint so children cannot reach them.
Pull the shoulder belt all the way out of the
retractor to set the lock, if your vehicle has
one, after the child restraint has been installed.
Be sure to follow the instructions of the child
restraint manufacturer.Notice:Contact between the child restraint LATCH
attachment parts and the vehicle’s safety belt
assembly may cause damage to these parts. Make
sure when securing unused safety belts behind
the child restraint that there is no contact between
the child restraint LATCH attachment parts and
the vehicle’s safety belt assembly.
Folding an empty rear seat with the safety belts
secured may cause damage to the safety belt or the
seat. When removing the child restraint, always
remember to return the safety belts to their normal,
stowed position before folding the rear seat.
1-51

Rollover capable roof-rail airbags are designed to help
contain the head and chest of occupants in the
outboard seating positions in the rst and second rows.
The rollover capable roof-rail airbags are designed to
help reduce the risk of full or partial ejection in rollover
events, although no system can prevent all such
ejections.
But airbags would not help in many types of collisions,
primarily because the occupant’s motion is not
toward those airbags. SeeWhen Should an Airbag
Inflate? on page 1-73for more information.
Airbags should never be regarded as anything more
than a supplement to safety belts.
What Will You See After an Airbag
Inates?
After the frontal airbags inate, they quickly deate, so
quickly that some people may not even realize an
airbag inated. Roof-rail airbags may still be at least
partially inated for some time after they deploy. Some
components of the airbag module may be hot for
several minutes. For location of the airbag modules, see
What Makes an Airbag Inflate? on page 1-74.
The parts of the airbag that come into contact with you
may be warm, but not too hot to touch. There may
be some smoke and dust coming from the vents in the
deated airbags. Airbag ination does not preventthe driver from seeing out of the windshield or being
able to steer the vehicle, nor does it prevent people from
leaving the vehicle.
{CAUTION:
When an airbag inates, there may be dust in
the air. This dust could cause breathing
problems for people with a history of asthma or
other breathing trouble. To avoid this, everyone
in the vehicle should get out as soon as it is
safe to do so. If you have breathing problems
but cannot get out of the vehicle after an airbag
inates, then get fresh air by opening a window
or a door. If you experience breathing problems
following an airbag deployment, you should
seek medical attention.
Your vehicle has a feature that may automatically
unlock the doors, turn the interior lamps on, and turn
the hazard warning ashers on when the airbags inate.
You can lock the doors, turn the interior lamps off,
and turn the hazard warning ashers off by using the
controls for those features.
1-75

A thick layer of additional material, such as a blanket or
cushion, or aftermarket equipment such as seat
covers, seat heaters, and seat massagers can affect
how well the passenger sensing system operates.
We recommend that you not use seat covers or other
aftermarket equipment other than any that GM has
approved for your specic vehicle. SeeAdding
Equipment to Your Airbag-Equipped Vehicle on
page 1-85for more information about modications that
can affect how the system operates.
{CAUTION:
Stowing of articles under the passenger’s seat
or between the passenger’s seat cushion and
seatback may interfere with the proper
operation of the passenger sensing system.
Servicing Your Airbag-Equipped
Vehicle
Airbags affect how your vehicle should be serviced.
There are parts of the airbag system in several places
around your vehicle. Your dealer/retailer and the service
manual have information about servicing your vehicle
and the airbag system. To purchase a service manual,
seeService Publications Ordering Information on
page 7-15.
{CAUTION:
For up to 10 seconds after the ignition is
turned off and the battery is disconnected, an
airbag can still inate during improper service.
You can be injured if you are close to an
airbag when it inates. Avoid yellow
connectors. They are probably part of the
airbag system. Be sure to follow proper
service procedures, and make sure the person
performing work for you is qualied to do so.
1-84

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

Tailgate
{CAUTION:
It is extremely dangerous to ride on the
tailgate, even when the vehicle is operated at
low speeds. People riding on the tailgate can
easily lose their balance and fall in response to
vehicle maneuvers. Falling from a moving
vehicle may result in serious injuries or death.
Do not allow people to ride on the tailgate. Be
sure everyone in your vehicle is in a seat and
using a safety belt properly.
On vehicles with a lock on the tailgate, use the key to
lock or unlock the tailgate.
Open the tailgate by lifting up on its handle while pulling
the tailgate toward you.
To shut the tailgate, rmly push it upward until it
latches.
After you put the tailgate back up, pull it back towards
you to be sure it latches securely.
Tailgate Removal
The tailgate can be removed to allow for different loading
situations. Although the tailgate can be removed without
assistance, you may want someone to assist you with the
removal to avoid possible damage to the vehicle.
To remove the tailgate, do the following:
1. Raise the tailgate
slightly and release
both retaining
cable clips. To release
the retaining cable
clips, lift the cable so it
points straight out.
Lift the clip over
the bolt, and push the
cable forward then
rotate down.
2. With the tailgate about halfway open, lift the right
edge of the tailgate from the lower pivot.
On vehicles with the tailgate assist feature, raise
the tailgate nearly all the way to the closed position
prior to removing the left edge.
3. Move the tailgate to the right to release the left edge.
Reverse this procedure to reinstall the tailgate. Make
sure the tailgate is secure.
2-14