2008 GMC SIERRA wiring

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

Q:What if I added a snow plow? Will it keep the
airbags from working properly?
A:We have designed our airbag systems to work
properly under a wide range of conditions,
including snow plowing with vehicles that have the
optional Snow Plow Prep Package (RPO VYU).
But do not change or defeat the snow plow’s
“tripping mechanism.” If you do, it can damage your
snow plow and your vehicle, and it may cause an
airbag ination.
Q:Because I have a disability, I have to get my
vehicle modied. How can I nd out whether
this will affect my airbag system?
A:If you have questions, call Customer Assistance.
The phone numbers and addresses for Customer
Assistance are in Step Two of the Customer
Satisfaction Procedure in this manual. See
Customer Satisfaction Procedure on page 7-2.
In addition, your dealer/retailer and the service manual
have information about the location of the airbag
sensors, sensing and diagnostic module and airbag
wiring.
1-86

Puddle Lamps
If your vehicle has puddle lamps, they come on when
the unlock button on the Remote Keyless Entry
(RKE) Transmitter is pressed. The lamps time out or
turn off once the engine is started.
Fog Lamps
-(Fog Lamps):If your vehicle has fog lamps, the
control is located next to the exterior lamps control
on the instrument panel, to the left of the steering
column.
The ignition must be in the ON/RUN position for the fog
lamps to come on.
Press the button to turn the fog lamps on or off. A light
will come on in the instrument panel cluster.
When the fog lamps are turned on, the parking lamps
automatically turn on.
When the headlamps are changed to high-beam, the
fog lamps also go off. When the high-beam headlamps
are turned off, the fog lamps will come on again.
Some localities have laws that require the headlamps to
be on along with the fog lamps.
Auxiliary Roof Mounted Lamp
If your vehicle has this feature, this button includes
wiring provisions for a dealer or a qualied service
center to install an auxiliary roof lamp.
This button is located on
the overhead console.
When the wiring is connected to an auxiliary roof
mounted lamp, pressing the bottom of the button will
activate the lamp and illuminate an indicator light at the
bottom of this button. Pressing the top of the button
will turn off the roof mounted lamp and indicator.
The emergency roof lamp circuit is fused at 30 amps,
so the total current draw of the attached lamps
should be less than this value. The attachment points
for the roof lamp circuits are two blunt cut wires located
above the overhead console, a dark green switched
power wire and a black ground wire.
For further information on roof mount emergency lamp
installation, please visit the GM Uptter website at
www.gmuptters.com or contact your dealer.
3-20

Airbag Readiness Light
There is an airbag readiness light on the instrument
panel cluster, which shows the airbag symbol. The
system checks the airbag’s electrical system for
malfunctions. The light tells you if there is an electrical
problem. The system check includes the airbag
sensor, the pretensioners, the airbag modules, the
wiring and the crash sensing and diagnostic module.
For more information on the airbag system, seeAirbag
System on page 1-68.
This light will come on
when you start your
vehicle, and it will ash
for a few seconds.
The light should go out
and the system is ready.
If the airbag readiness light stays on after you start the
vehicle or comes on when you are driving, your
airbag system may not work properly. Have your vehicle
serviced right away.{CAUTION:
If the airbag readiness light stays on after you
start your vehicle, it means the airbag system
may not be working properly. The airbags in
your vehicle may not inate in a crash, or they
could even inate without a crash. To help
avoid injury to yourself or others, have your
vehicle serviced right away if the airbag
readiness light stays on after you start your
vehicle.
The airbag readiness light should ash for a few
seconds when you start the engine. If the light does not
come on then, have it xed immediately. If there is a
problem with the airbag system, an airbag Driver
Information Center (DIC) message may also come on.
SeeDIC Warnings and Messages on page 3-63for
more information.
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The following are the possible messages that can be
displayed and some information about them.
If your vehicle has the DURAMAX
®Diesel engine, see
the DURAMAX®Diesel manual for more information.
CHANGE ENGINE OIL SOON
This message displays when the engine oil needs to be
changed. When you change the engine oil, be sure
to reset the CHANGE ENGINE OIL SOON message.
SeeEngine Oil Life System on page 5-18for information
on how to reset the message. SeeEngine Oil (Gasoline
Engine) on page 5-15andScheduled Maintenance
(Gasoline Engine) on page 6-4for more information.
CHECK TIRE PRESSURE
If your vehicle has the Tire Pressure Monitor System
(TPMS), this message displays when the pressure
in one or more of the vehicle’s tires needs to be
checked. This message also displays LEFT FRONT,
RIGHT FRONT, LEFT REAR, or RIGHT REAR to
indicate which tire needs to be checked. You can
receive more than one tire pressure message at a time.
To read the other messages that may have been
sent at the same time, press the set/reset button or the
trip odometer reset stem. If a tire pressure message
appears on the DIC, stop as soon as you can. Have the
tire pressures checked and set to those shown on the
Tire Loading Information label. SeeTires on page 5-66,Loading Your Vehicle on page 4-36, andInflation - Tire
Pressure on page 5-74. The DIC also shows the tire
pressure values. See “DIC Operation and Displays (With
DIC Buttons)” earlier in this section. If the tire pressure
is low, the low tire pressure warning light comes on.
SeeTire Pressure Light on page 3-47.
CHECK TRAILER WIRING
On vehicles with the Integrated Trailer Brake Control
(ITBC) system, this message may display and a chime
may sound when one of the following conditions exists:
A trailer with electric brakes becomes disconnected
from the vehicle.
If the disconnect occurs while the vehicle is
stopped, this message clears itself after a
short time.
If the disconnect occurs while the vehicle is
moving, this message stays on until the ignition
is turned off.
There is a short in the wiring to the electric trailer
brakes.
When this message displays, power is no longer
available to the trailer brakes.
As soon as it is safe to do so, carefully pull your vehicle
over to the side of the road and turn the ignition off.
Check the wiring connection to the trailer and turn the
ignition back on. This message clears if the trailer
3-64

SERVICE THEFT DETERRENT SYSTEM
This message displays when there is a problem with
the theft-deterrent system. The vehicle may or may not
restart so you may want to take the vehicle to your
dealer/retailer before turning off the engine. See
PASS-Key
®III+ Operation on page 2-20for more
information.
SERVICE TIRE MONITOR SYSTEM
If your vehicle has the Tire Pressure Monitor System
(TPMS), this message displays if a part on the system is
not working properly. The tire pressure light also
ashes and then remains on during the same ignition
cycle. SeeTire Pressure Light on page 3-47. Several
conditions may cause this message to appear. SeeTire
Pressure Monitor Operation on page 5-78for more
information. If the warning comes on and stays on, there
may be a problem with the TPMS. See your
dealer/retailer.
SERVICE TRACTION CONTROL
If your vehicle has StabiliTrak®, this message displays
when there is a problem with the Traction Control
System (TCS). When this message displays, the system
will not limit wheel spin. Adjust your driving accordingly.
See your dealer/retailer for service. SeeStabiliTrak
®
System on page 4-6for more information.
SERVICE TRAILER BRAKE SYSTEM
On vehicles with the Integrated Trailer Brake Control
(ITBC) system, this message displays and a chime
sounds when there is a problem with the ITBC system.
When this message displays, power is no longer
available to the trailer brakes.
As soon as it is safe to do so, carefully pull your vehicle
over to the side of the road and turn the ignition off.
Check the wiring connection to the trailer and turn the
ignition back on. If this message still displays, either your
vehicle or the trailer needs service. See your
dealer/retailer.
See “Integrated Trailer Brake Control System” under
Towing a Trailer on page 4-55for more information.
3-69

Total vehicle reserve capacity is the difference between
your GVWR and the weight of your truck with full fuel
and passengers. It is the amount of weight you can add
to your vehicle before reaching your GVWR. Keep in
mind that reserve capacity numbers are intended
as a guide when selecting the amount of equipment or
cargo your truck can carry. If you are unsure of your
vehicle’s front, rear, or total weight, go to a weigh station
and weigh your vehicle. Your dealer/retailer can also
help you with this.
The total vehicle reserve capacity for your vehicle can
be found in the lower right corner of the Certication/Tire
label as shown previously.
See your dealer/retailer for additional advice and
information about using a snow plow on your vehicle.
Also, seeLoading Your Vehicle on page 4-36.
Emergency Roof Lamp Provisions
Vehicles with the RPO VYU snow plow prep package
also have an emergency roof lamp provision package,
RPO TRW. Wiring for the emergency roof lamp is
provided above the overhead console. SeeAuxiliary
Roof Mounted Lamp on page 3-20for switch location.
Truck-Camper Loading Information
A vehicle specic Truck-Camper Loading
information label is attached to the inside of your
vehicle’s glove box. This label will tell you if
your vehicle can carry a slide-in camper, how
much of a load your vehicle can carry, and how to
correctly spread out the load. Also, it will help
you match the right slide-in camper to your vehicle.
When you carry a slide-in camper, the total
cargo load of your vehicle is the weight of the
camper, plus the following:
Everything else added to the camper after it
left the factory
Everything in the camper
All the people inside
The Cargo Weight Rating (CWR) is the maximum
weight of the load your vehicle can carry. It
does not include the weight of the people inside.
But, you can gure about 150 lbs (68 kg) for
each seat.
The total cargo load must not be more than your
vehicle’s CWR.
4-47

TRAILER GAIN – This setting is displayed anytime the
Trailer Brake Display Page is active. This setting
can be adjusted from 0.0 to 10.0 with either a trailer
connected or disconnected. To adjust the Trailer Gain,
press one of the Trailer Gain adjustment buttons
located on the Trailer Brake Control Panel. Press and
hold a gain button to cause the Trailer Gain to
continuously adjust. To turn the output to the trailer off,
adjust the Trailer Gain setting to 0.0 (zero).
0.0 (zero) gain is the factory default setting. To properly
adjust trailer gain, see the Trailer Gain Adjustment
Procedure later in this section.
TRAILER OUTPUT – This is displayed any time a trailer
with electric brakes is connected. Output to the electric
brakes is based on the amount of vehicle braking
present and relative to the Trailer Gain setting. Output is
displayed from 0 to 10 bars for each gain setting.
The Trailer Output will indicate “------“ontheTrailer
Brake Display Page whenever the following occur:
No trailer is connected.
A trailer without electric brakes is connected (no
DIC message is displayed).
A trailer with electric brakes has become
disconnected (a CHECK TRAILER WIRING
message will also be displayed on the DIC).
There is a fault present in the wiring to the electric
trailer brakes (a CHECK TRAILER WIRING
message will also be displayed on the DIC).
There is a fault in the ITBC system (a SERVICE
TRAILER BRAKE SYSTEM message will also
be displayed in the DIC).
Manual Trailer Brake Apply
The Manual Trailer Brake Apply Lever is located on the
Trailer Brake Control Panel and is used to apply the
trailer’s electric brakes independent of your vehicle’s
brakes. This lever is used in the Trailer Gain Adjustment
Procedure to properly adjust the power output to the
trailer brakes. Sliding the lever to the left will apply only
the trailer brakes. The power output to the trailer is
indicated in the Trailer Brake Display Page in the DIC.
If your vehicle’s service brakes are applied while
using the Manual Trailer Brake Apply Lever, the trailer
output power will be the greater of the two.
The trailer and the vehicle’s brake lamps will come on
when either vehicle braking or manual trailer brakes
are applied.
4-82