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Towing
Towing Your Vehicle
Consult your dealer or a professional towing service if
you need to have your disabled vehicle towed. See
Roadside Assistance Program on page 7-5.
Releasing Air-Operated Parking Brakes
If your vehicle has air brakes, you could have a
special towing problem. If your vehicle has to be towed
because of a complete loss of air pressure from
both systems, the parking brakes will have automatically
engaged. The tow operator can release the brakes
manually by using the following steps. Then your vehicle
can be towed with all wheels or only the rear wheels
on the ground.
1. Block the wheels of the vehicle.2. Remove the release stud and nut from the side of
the brake chamber. Some chambers have studs
which are visible at all times.
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3. Remove the rubber
cap from the rear of
the chamber.
4. Put the release stud, nut and flat washer into
the chamber.
5. Turn the stud clockwise a quarter of a turn.6. Turn the stud nut
clockwise several turns
to release the brakes.
Follow the same
procedure to release
the other brake
or brakes.
7. At the repair facility, apply air pressure of at least
70 psi (480 kPa) to the brake chambers, either
from an external air supply or the vehicle’s
air system.
8. Turn the stud nut counterclockwise several turns.
Remove the stud from the chamber.
9. Replace the stud and washer and tighten the nut
into the side of the chamber.
10. Replace the rubber cap.
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Trailer Connections
Heavy-Duty Trailer Wiring Package
Your vehicle may be equipped with an eight-wire trailer
towing harness. This harness, with a seven-pin
universal heavy-duty trailer connector, is attached to a
bracket on the platform hitch.
The Center High-Mounted Stoplamp (CHMSL) wire is
tied next to the trailer wiring harness for use with a
trailer.
The eight-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
•Light Blue: CHMSL
•Red: Battery Feed
•Dark Blue: Trailer Brake
Trailer Connections
(C7/C8 Models Only)
If your vehicle has these trailer connections, they are
located at the rear of the cab for a tractor and at the rear
of the chassis when towing a trailer. There will be an
air connection and an electrical connection.
Be sure that the couplings to the trailer are made
correctly.
Air Connections
If you are not connecting the trailer air line connections
to another piece of equipment, be sure to replace
their protective caps.
Electrical Connections
This system is a seven-wire cable that will connect to
the trailer, supplying power to the trailer’s lighting
system. When not in use, it is stored in the trailer
air-hose storage bracket.
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Page 229 of 398

Service............................................................5-3
California Proposition 65 Warning.....................5-3
Doing Your Own Service Work.........................5-4
Engine Fan Breakage.....................................5-5
Fuel................................................................5-6
Gasoline Octane............................................5-6
Gasoline Specifications....................................5-6
Additives.......................................................5-6
Diesel Engine Fuel.........................................5-7
What Fuel to Use...........................................5-8
Very Cold Weather Operation.........................5-10
Water in Fuel...............................................5-10
Running Out of Fuel.....................................5-17
Fuel Filter Replacement.................................5-18
Fuels in Foreign Countries.............................5-19
Filling the Tank............................................5-20
Filling a Portable Fuel Container.....................5-21
Checking Things Under the Hood....................5-22
Hood Latches...............................................5-22
Engine Oil (Caterpillar
®Diesel Engine).............5-24
Engine Oil (DURAMAX®Diesel)......................5-24
Engine Oil (Gasoline Engine)..........................5-28
Engine Oil Life System (Gasoline Engine)........5-31
Engine Oil Life System (DURAMAX
®Diesel).....5-33
Engine Oil Life System
(Caterpillar
®Diesel Engine).........................5-34Engine Air Cleaner/Filter................................5-35
Automatic Transmission Fluid.........................5-36
Manual Transmission Fluid.............................5-37
Engine Coolant
(Gas and DURAMAX
®Engines)...................5-38
Engine Coolant (Caterpillar®Diesel Engines).....5-40
Coolant Surge Tank Pressure Cap..................5-40
Engine Overheating.......................................5-40
Cooling System
(Gas and DURAMAX
®Engines)...................5-42
Engine Fan Noise.........................................5-47
Power Steering Fluid.....................................5-47
Windshield Washer Fluid................................5-48
Brakes........................................................5-49
Battery........................................................5-58
Jump Starting...............................................5-59
Rear Axle.......................................................5-64
Rear Axle Shift Motor....................................5-65
Four-Wheel Drive............................................5-65
Front Axle......................................................5-66
Noise Control System.....................................5-67
Tampering with Noise Control System
Prohibited.................................................5-67
Bulb Replacement..........................................5-68
Windshield Wiper Blade Replacement..............5-69
Section 5 Service and Appearance Care
5-1
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Other Service Items........................................5-70
Fuel Filter....................................................5-70
Primary Fuel Filter and Water Separator..........5-71
Secondary Fuel Filter and Water
Separator/Heater (Caterpillar
®Diesel)...........5-71
Automatic Ether Injection System
(Caterpillar
®Diesel)....................................5-72
Front Wheel Bearings with Oil-Filled Hubs........5-73
Air Conditioning System.................................5-74
Tires..............................................................5-74
Inflation - Tire Pressure.................................5-75
Wheel Loading.............................................5-75
Dual Tire Operation.......................................5-76
When It Is Time for New Tires.......................5-76
Wheel Alignment and Tire Balance..................5-77
Tightening the Wheel Nuts.............................5-77
Wheel Replacement......................................5-81
If a Tire Goes Flat........................................5-82
Appearance Care............................................5-83
Cleaning the Inside of Your Vehicle.................5-83
Fabric/Carpet...............................................5-85
Instrument Panel, Vinyl, and Other Plastic
Surfaces..................................................5-86
Care of Safety Belts......................................5-86
Weatherstrips...............................................5-86
Washing Your Vehicle...................................5-87Cleaning Exterior Lamps/Lenses.....................5-87
Finish Care..................................................5-87
Windshield and Wiper Blades.........................5-88
Aluminum or Chrome-Plated Wheels................5-89
Tires...........................................................5-89
Sheet Metal Damage.....................................5-89
Finish Damage.............................................5-89
Underbody Maintenance................................5-90
Chemical Paint Spotting.................................5-90
Vehicle Identi cation......................................5-91
Vehicle Identification Number (VIN).................5-91
Service Statement.........................................5-92
Service Parts Identification Label.....................5-92
Electrical System............................................5-92
Add-On Electrical Equipment..........................5-92
Headlamp Wiring..........................................5-93
Windshield Wiper Fuses................................5-93
Fusible Links................................................5-93
Power Windows and Other Power Options.......5-93
Fuses and Circuit Breakers............................5-93
Instrument Panel Fuse Block..........................5-94
Underhood Fuse Block..................................5-96
Capacities and Speci cations..........................5-99
Normal Maintenance Replacement Parts.........5-104
Section 5 Service and Appearance Care
5-2
Page 231 of 398
Service
Your dealer knows your vehicle best and wants you to
be happy with it. We hope you will go to your dealer
for all your service needs. You will get genuine GM parts
and GM-trained and supported service people.
We hope you will want to keep your GM vehicle all GM.
Genuine GM parts have one of these marks:
California Proposition 65 Warning
Most motor vehicles, including this one, contain and/or
emit chemicals known to the State of California to
cause cancer and birth defects or other reproductive
harm. Engine exhaust, many parts and systems
(including some inside the vehicle), many fluids, and
some component wear by-products contain and/or emit
these chemicals.
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Doing Your Own Service Work
{CAUTION:
You can be injured and your vehicle could be
damaged if you try to do service work on a
vehicle without knowing enough about it.
Be sure you have sufficient knowledge,
experience, the proper replacement parts,
and tools before you attempt any vehicle
maintenance task.
Be sure to use the proper nuts, bolts, and
other fasteners. English and metric
fasteners can be easily confused. If you
use the wrong fasteners, parts can later
break or fall off. You could be hurt.If you want to do some of your own service work, you
will want to use the proper service manual. It tells
you much more about how to service your vehicle than
this manual can. To order the proper service manual,
seeService Publications Ordering Information on
page 7-11.
Your vehicle has an airbag system. Before attempting to
do your own service work, seeServicing Your
Airbag-Equipped Vehicle on page 1-61.
You should keep a record with all parts receipts and list
the mileage and the date of any service work you
perform. SeePart D: Maintenance Record on page 6-35.
5-4