Page 370 of 536
Heavy-Duty Trailer Wiring Harness
Package
Your vehicle is equipped with the seven-wire trailer
towing harness. This harness with a seven-pin
universal trailer connector is attached to a bracket on
the hitch platform.The seven-wire harness contains the following
trailer circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn Signal
Brown: Taillamps
White: Ground
Light Green: Back-up Lamps
Red: Battery Feed**
Dark Blue: Trailer Brake
**If you are charging a remote (non-vehicle) battery,
turn on the headlamps to boost the vehicle system
voltage and properly charge the battery.
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Service............................................................5-3
Doing Your Own Service Work.........................5-4
Adding Equipment to the Outside of
Your Vehicle..............................................5-4
Fuel................................................................5-5
Gasoline Octane............................................5-5
Gasoline Speci cations....................................5-5
California Fuel...............................................5-5
Additives.......................................................5-6
Fuel E-85 (85% Ethanol).................................5-6
Fuels in Foreign Countries...............................5-8
Filling the Tank..............................................5-8
Filling a Portable Fuel Container.....................5-10
Checking Things Under the Hood....................5-10
Hood Release..............................................5-11
Engine Compartment Overview.......................5-12
Engine Oil...................................................5-16
Engine Oil Life System..................................5-19
Engine Air Cleaner/Filter................................5-21
Automatic Transmission Fluid.........................5-23
Engine Coolant.............................................5-26
Coolant Surge Tank Pressure Cap..................5-28
Engine Overheating.......................................5-28
Overheated Engine Protection
Operating Mode........................................5-30Cooling System............................................5-30
Engine Fan Noise.........................................5-35
Power Steering Fluid.....................................5-36
Windshield Washer Fluid................................5-37
Brakes........................................................5-38
Battery........................................................5-41
Jump Starting...............................................5-42
All-Wheel Drive..............................................5-47
Rear Axle.......................................................5-48
Four-Wheel Drive............................................5-49
Front Axle......................................................5-50
Bulb Replacement..........................................5-52
Halogen Bulbs..............................................5-52
Headlamps..................................................5-52
Front Turn Signal, Sidemarker and Daytime
Running Lamps.........................................5-53
Side Identi cation Marker Lamps.....................5-54
Roof Marker Lamps......................................5-55
Taillamps, Turn Signal, Stoplamps and
Back-up Lamps.........................................5-57
Replacement Bulbs.......................................5-58
Windshield Wiper Blade Replacement..............5-59
Section 5 Service and Appearance Care
5-1
Page 426 of 536
Bulb Replacement
For the proper type of replacement bulbs, see
Replacement Bulbs on page 5-58.
For any bulb changing procedure not listed in this
section, contact your dealer.
Halogen Bulbs
{CAUTION:
Halogen bulbs have pressurized gas inside
and can burst if you drop or scratch the bulb.
You or others could be injured. Be sure to read
and follow the instructions on the bulb
package.
Headlamps
To replace a headlamp bulb, do the following:
1. Open the hood. SeeHood Release on page 5-11
for more information.
2. Remove the two pins on the top of the headlamp
assembly. To remove them, turn the outer pin
outward and pull it straight up. To remove the inner
pin, turn it inward and pull it straight up.
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Page 427 of 536
A. Low-Beam Headlamp
B. High-Beam Headlamp
3. Pull the headlamp assembly out.
4. Unplug the electrical connector.
5. Turn the bulb counterclockwise and remove it from
the headlamp assembly.
6. Put the new bulb into the headlamp assembly and
turn it clockwise until it is tight. Use care not to
touch the bulb with your ngers or hands.
7. Plug in the electrical connector.
8. Put the headlamp assembly back into the vehicle.
9. Install and turn the two pins into the locking feature.
Front Turn Signal, Sidemarker and
Daytime Running Lamps
A. Sidemarker Lamp
B. Retainer Clip
C. Front Turn
Signal LampD. Daytime Running
Lamp (DRL)
To replace a front turn signal, sidemarker or DRL bulb,
do the following:
1. Open the hood. SeeHood Release on page 5-11
for more information.
2. Remove the headlamp assembly as described
previously. SeeHeadlamps on page 5-52for
more information.
5-53
Page 428 of 536

3. Press the retainer clip (B), located behind the turn
signal assembly, towards the outside of the vehicle.
4. Pull the turn signal assembly out of the vehicle.
5. Press the locking release lever, turn the bulb socket
counterclockwise and remove it from the turn signal
assembly.
6. Remove the old bulb from the bulb socket.
7. Install a new bulb into the bulb socket.
8. Insert the bulb socket into the turn signal assembly
and turn it clockwise until it locks.9. Reinstall the turn signal assembly back into the
vehicle placing the hook and posts on the inner side
into the alignment holes rst, then the outer side into
the retainer bracket until you hear a click.
10. Reinstall the headlamp assembly.
Side Identi cation Marker Lamps
To replace a side identi cation marker bulb, do
the following:
1. Locate the lamp gasket near the rear wheel to
expose the service slot and pull back the edge.
2. Using a at tool, push into the slot to release the
lamp housing.
3. Pull the housing out to expose the wiring harness
and connector.
4. Unplug the lamp assembly harness from the
housing.
5. Unplug the lamp.
6. Put in a new lamp and snap it into the housing.
7. Reinstall the lamp housing.
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Page 432 of 536
4. Pull the old bulb
straight out from the
socket.
5. Press a new bulb into the socket, insert the socket
into the taillamp housing and turn the socket
clockwise into the taillamp housing until it clicks.
6. Reinstall the taillamp assembly.Replacement Bulbs
Exterior Lamp Bulb Number
Back-up Lamp 3157
Daytime Running Lamps (DRL) 4114K
Front Roof Marker Lamp 194
Front Parking and Turn Lamp 3457A
Headlamps
High-Beam 9005
Low-Beam 9006
Rear Marker Lamp, Taillamp and
Stoplamp3157
Rear Turn Signal Lamp 3157
For replacement bulbs not listed here, contact your
dealer.
5-58
Page 449 of 536

Each new wheel should have the same load-carrying
capacity, diameter, width, offset and be mounted
the same way as the one it replaces.
If you need to replace any of your wheels, wheel bolts
or wheel nuts, replace them only with new GM
original equipment parts. This way, you will be sure to
have the right wheel, wheel bolts and wheel nuts
for your vehicle.
{CAUTION:
Using the wrong replacement wheels, wheel
bolts or wheel nuts on your vehicle can be
dangerous. It could affect the braking and
handling of your vehicle, make your tires lose
air and make you lose control. You could have
a collision in which you or others could be
injured. Always use the correct wheel, wheel
bolts and wheel nuts for replacement.Notice:The wrong wheel can also cause problems
with bearing life, brake cooling, speedometer or
odometer calibration, headlamp aim, bumper height,
vehicle ground clearance and tire or tire chain
clearance to the body and chassis.
SeeChanging a Flat Tire on page 5-78for more
information.
Used Replacement Wheels
{CAUTION:
Putting a used wheel on your vehicle is
dangerous. You cannot know how it has been
used or how far it has been driven. It could fail
suddenly and cause a crash. If you have to
replace a wheel, use a new GM original
equipment wheel.
5-75
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Fuses Usage
IGN 1 Ignition Relay
PCM 1 Powertrain Control Module
ETC/ECMElectronic Throttle Control,
Electronic Brake Controller
IGN EInstrument Panel Cluster,
Air Conditioning Relay,
Turn Signal/Hazard Switch,
Starter Relay
RTD Ride Control
TRL B/U Backup Lamps Trailer Wiring
PCM BPowertrain Control Module,
Fuel Pump
F/PMP Fuel Pump (Relay)
B/U LPBack-up Lamps, Automatic
Transmission Shift Lock
Control System
RR DEFOG Rear Window Defogger
HDLP-HI Headlamp High Beam Relay
PRIME Not Used
AIRBAGSupplemental In atable
Restraint System
FRT PARKFront Parking Lamps,
Sidemarker Lamps
DRLDaytime Running
Lamps (Relay)Fuses Usage
SEO IGN Rear Defog Relay
TBC IGN1 Truck Body Controller Ignition
HI HDLP - LT High Beam Headlamp - Left
LH HID Not Used
DRL Daytime Running Lamps
RVC Regulated Voltage Control
IPC/DICInstrument Panel
Cluster/Driver Information
Center
HVAC/ECAS Climate Control Controller
CIG LTR Cigarette Lighter
HI HDLP - RT High Beam Headlamp - Right
HDLP - LOW Headlamp Low Beam Relay
A/C COMP Air Conditioning Compressor
A/C COMPAir Conditioning
Compressor Relay
RR WPR Rear Wiper/Washer
RADIO Audio System
SEO B1Mid Bussed Electrical Center,
HomeLink, Rear Heated
Seats
LO HDLP - LT Headlamp Low Beam - Left
BTSIBrake Transmission Shift
Interlock System
5-114