2008 GMC SIERRA ECU

Adding Equipment to Your
Airbag-Equipped Vehicle
Q:Is there anything I might add to or change
about the vehicle that could keep the airbags
from working properly?
A:Yes. If you add things that change your vehicle’s
frame, bumper system, height, front end or side
sheet metal, they may keep the airbag system from
working properly. Changing or moving any parts
of the front seats, safety belts, the airbag sensing
and diagnostic module, steering wheel, instrument
panel, roof-rail airbag modules, ceiling headliner
or pillar garnish trim, overhead console, front
sensors, rollover sensor module, or airbag wiring
can affect the operation of the airbag system.
In addition, your vehicle may have a passenger
sensing system for the right front passenger’s
position, which includes sensors that are part of the
passenger’s seat. The passenger sensing system
may not operate properly if the original seattrim is replaced with non-GM covers, upholstery or
trim, or with GM covers, upholstery or trim
designed for a different vehicle. Any object, such as
an aftermarket seat heater or a comfort enhancing
pad or device, installed under or on top of the
seat fabric, could also interfere with the operation of
the passenger sensing system. This could either
prevent proper deployment of the passenger
airbag(s) or prevent the passenger sensing system
from properly turning off the passenger airbag(s).
SeePassenger Sensing System on page 1-80.
If you have any questions about this, you should
contact Customer Assistance before you modify
your vehicle. The phone numbers and addresses for
Customer Assistance are in Step Two of the
Customer Satisfaction Procedure in this manual.
SeeCustomer Satisfaction Procedure on page 7-2.
If your vehicle has rollover roof-rail airbags, see
Different Size Tires and Wheels on page 5-86
for additional important information.
1-85

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

This feature will not operate if the key is in the ignition.
You can program this feature using the Driver
Information Center (DIC). See DELAY DOOR LOCK
underDIC Vehicle Customization (With DIC Buttons) on
page 3-72.
Programmable Automatic Door
Locks
Vehicles with an automatic lock/unlock feature enable
you to program the vehicle’s power door locks. You can
program this feature through the Driver Information
Center (DIC). SeeDIC Vehicle Customization (With DIC
Buttons) on page 3-72for more information on DIC
programming.
Rear Door Security Locks
Your vehicle has rear door security locks. These
prevent passengers from opening the rear doors from
the inside.The rear door security
locks are located on the
inside edge of each
rear door.
The rear doors must be open to access them. The
label showing lock and unlock positions is located near
the lock.
To set the locks, do the following:
1. Insert the key into the security lock slot and turn it
so the slot is in the horizontal position.
2. Close the door.Security Lock Label
shown
2-11

When you want to open a rear door when the security
lock is on, do the following:
1. Unlock the door by lifting the rear door manual lock,
using the power door lock switch, or the Remote
Keyless Entry (RKE) transmitter, if the vehicle
has one.
2. Open the door from the outside.
To cancel the rear door security lock, do the following:
1. Unlock the door and open it from the outside.
2. Insert the key into the security lock slot and turn it
so the slot is in the vertical position.Lockout Protection
This feature protects you from locking the key in the
vehicle when the key is in the ignition and a front door
is open.
If the driver’s side power door lock switch is pressed
when the driver’s door is open and the key is in
the ignition, all of the doors will lock and then the driver’s
door will unlock.
If the passenger’s side power door lock switch is
pressed when the front passenger’s door is open and
the key is in the ignition, all of the doors will lock
and then the front passenger’s door will unlock.
2-12

Rear Doors
Extended Cab
Your vehicle may have a rear access door(s) that allows
easier access to the rear area of the extended cab.
To open a rear access
door from the outside, rst
open the front door.
Then, use the handle
located on the front edge
of the rear access door
to open it.
You must fully close a rear access door before you can
close the front door.To open a rear access
door from the inside, the
front door must be opened
rst. Then, use the
handle located on the
inside of the rear access
door to open.
Crew Cabs
If your vehicle is a crew cab, you can open your doors
from the inside or outside. Your vehicle may also
have a feature which prevents children from opening the
rear doors. SeeRear Door Security Locks on page 2-11
for more information.
2-13

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

Sun Visors
Pull the sun visor down to block glare. Swing the sun
visor to the side to cover the side window.
The passenger’s side sun visor may have a vanity
mirror.
Theft-Deterrent Systems
Vehicle theft is big business, especially in some cities.
Although your vehicle has a number of theft-deterrent
features, we know that nothing we put on it can make it
impossible to steal.
Content Theft-Deterrent
Your vehicle may have a content theft-deterrent alarm
system.
This is the security light.To arm the theft-deterrent system:
1. Open the door.
2. Lock the door with the Remote Keyless Entry (RKE)
transmitter. The security light should come on and
ash.
If the delayed locking feature is active, the alarm
will not be activated until all doors are closed
and the security light goes off.
3. Close all doors. The security light will stop ashing
and go off after approximately 30 seconds. The
content theft deterrent alarm is not armed until the
security light goes off.
If a locked door is opened without using the RKE
transmitter, a ten second pre-alarm will occur. The horn
will chirp and the lights will ash. If the key is not
placed in the ignition and turned to START or the door
is not unlocked by pressing the unlock button on the
RKE transmitter during the ten second pre-alarm,
the alarm will go off. Your vehicle’s headlamps will ash
and the horn will sound for about two minutes, then
will turn off to save the battery power.
2-18

The theft-deterrent system will not activate if the doors
are locked with the vehicle’s key or the manual door
lock. It activates only if you use the power door
lock switch with the door open or the RKE transmitter.
You should also remember that you can start your
vehicle with the correct ignition key if the alarm has been
set off.
To avoid setting off the alarm by accident:
If you do not want to activate the theft-deterrent
system, the vehicle should be locked with the
door key after the doors are closed.
Always unlock a door with the RKE transmitter.
Unlocking a door any other way will set off the alarm
if the system has been armed.
If you set off the alarm by accident, press unlock on the
RKE transmitter or place the key in the ignition and
turn it to START to turn it off.
Testing the Alarm
To test the alarm:
1. From inside the vehicle, lower the driver’s window
and open the driver’s door.
2. Activate the system by locking the doors with the
RKE transmitter.
3. Get out of the vehicle, close the door and wait for
the security light to go out.
4. Then reach in through the window, unlock the door
with the manual door lock and open the door. This
should set off the alarm.
If the alarm does not sound when it should but the
headlamps ash, check to see if the horn works. The
horn fuse may be blown. To replace the fuse, seeFuses
and Circuit Breakers on page 5-123.
If the alarm does not sound or the headlamps do not
ash, see your dealer/retailer for service.
2-19