
Power Windows and Other Power
Options
Circuit breakers in the fuse panel protect the power
windows and other power accessories. When the current
load is too heavy, the circuit breaker opens. This
protects the circuit until the current load returns to
normal or the problem is fixed.
Fuses and Circuit Breakers
The wiring circuits in the vehicle are protected from
short circuits by a combination of fuses, circuit breakers,
maxi-fuses and fusible links. This greatly reduces the
chance of a fire caused by an electrical problem. There
may be a fuse taped to the wiring harness near the
hydraulic brake booster.
Instrument Panel Fuse Block
There are two instrument panel fuse blocks located
behind the instrument panel on the passenger side of
the vehicle.
Be sure to replace fuses with fuses of the same rating.
Do not use fuses of higher amperage than those
indicated on the fuse block.
5-96

Fuse Usage
1 Stoplamps
2 Not Used
3 Parking Lamps
4 Powertrain Control Module
5 Auxiliary Wiring
6 Heater/Air Conditioning
7 Hazard Warning Flashers
8 Power PostFuse Usage
9 Courtesy Lamps
10Warning Lights, Gages and
Indicators
11 Starter
12 Rear Axle/Four-Wheel-Drive
13Trailer Turn Signals/Hazard Warning
Flashers
14 Radio/Chime
15 Daytime Running Lamps
5-97

Fuse Usage
16 Airbag System
17 Exterior/Interior Lamps
18 Parking Brake
19 Accessory Power
20 Ignition 4
21 Sidemarker Lamps
22 Turn Signal/Backup Lamps
23 Transmission
24 Hydraulics/Air Brake
A Spare
B Spare
Fuse Usage
Blank Not Used
BRK Brake Warning Lamp
RT PRK Passenger Side Parking Lamps
Blank Not Used
Blank Not Used
LT PARK Driver Side Parking Lamps
RT REAR
TRN/STOPPassenger Side Rear Turn
Signal/Stoplamp
LT REAR
TRN/STOPDriver Side Rear Turn
Signal/Stoplamp
Fuse Usage
RADIO Radio
Blank Not Used
Blank Not Used
PWR WNDW Power Windows
Relay Usage
ECU/PTO*Engine Control Unit/Power Take-Off
*Diesel 7.8 Duramax
BRK LAMPC4/C5 Brake Lamps,
C6/C7/C8 Tractor/Trailer Wiring
DRL Daytime Running Lamps
IGN-4 Ignition
CHMSL Center High Mounted Stoplamp
MRK LTS Sidemarker and Clearance Lamps
HTD/MIRR Heated Mirrors
HTR Diesel Heated Fuel
RT TRN TRLR Passenger Side Trailer Turn Signal
Blank Not Used
LT TRN TRLR Driver Side Trailer Turn Signal
Blank Not Used
Blank Not Used
Blank Not Used
5-98

(24)= Evaporative Control System Service, if equipped:
Check all fuel and vapor lines and hoses for proper
connections and correct routing (or every 24 months,
whichever occurs first). Replace parts as needed.
(25)= Replace spark plugs. Inspect wires for damage.
Check the wire boot and boot heat shield fit at spark
plugs and coil. Replace parts as needed.
(26)= Check the fuel tank, fuel cap and fuel lines for
damage which could cause leakage. Inspect fuel cap for
correct sealing ability and any indications of damage.
Check fuel cap gasket for even filler neck imprint.
Replace parts as needed.
(27)= Check Exhaust Gas Recirculation (EGR) system
as described in the service manual. SeeService
Publications Ordering Information on page 7-10.
(28)= Inspect Electronic Vacuum Regulator Valve
(EVRV) filter for excessive contamination or plugging.
If needed, clean filter with solution of soap and water, let
dry and install.
(29)= Drain, flush, and refill cooling system. This service
can be complex; you should have your dealer/retailer
perform this service. SeePart C: Recommended Fluids
and Lubricants on page 6-31for what to use. Inspect
hoses. Clean radiator, condenser, pressure cap, and
neck. Pressure test cooling system and pressure cap.
For Caterpillar
®diesel engines, always refer to the
Caterpillar®Diesel Engine Operation & Maintenance
Manual for coolant recommendations and change
intervals.(30)= Change the lubricant. SeePart C: Recommended
Fluids and Lubricants on page 6-31.
(31)= Front axle service: Re-pack upper kingpin roller
bearing.
(32)= Air brake service:
•Inspect brake lines and hoses for proper hook-up,
binding, leaks, cracks, chafing, etc. Inspect drum
brake linings for wear or cracks. Inspect other brake
parts at each wheel, including drums and wheel
speed sensor wiring. Check brake pedal for
excessive free play or travel (or every 6 months,
whichever occurs first) and have serviced if needed.
Check brakes more often if driving habits and
conditions result in frequent braking. Replace air
dryer cartridge only if excessive oil or moisture is
present. A small amount of oil in the system is normal
and should not be considered as a reason to replace
the cartridge.
•Test air lines for leaks; tighten as needed. Replace
compressor filter.
•Inspect air parking brake chamber for leaks and
damage. Inspect lines and hoses for leaks, cracks,
chafing, etc. Also check all attachments for tightness,
wear, or damage. Note: The spring brake section of
the rear brake diaphragms are non-serviceable.
6-24

Diesel Engine.................................................2-26
Engine Alarm and Automatic Shutdown...........2-18
Exhaust Restrictor.......................................2-22
Fuel............................................................ 5-8
High Idle System.........................................2-20
Starting......................................................2-14
Diesel Particulate Filter....................................2-46
Diesel Particulate Filter Warning Light................3-46
Differential Lock Control, Rear Axle..................... 4-7
Differential Lock Indicator Light.........................3-41
Doing Your Own Service Work........................... 5-5
Dome Lamps .................................................3-16
Door
Locks.......................................................... 2-6
Power Door Locks......................................... 2-7
Driving
At Night.....................................................4-13
Defensive..................................................... 4-2
Drunken....................................................... 4-3
Highway Hypnosis.......................................4-15
Hill and Mountain Roads..............................4-16
In Rain and on Wet Roads...........................4-14
Rocking Your Vehicle to Get it Out.................4-19
Tow Hooks.................................................4-20
Winter........................................................4-17
Driving for Better Fuel Economy......................... 4-2
Dual Tire Operation.........................................5-78E
EDR .............................................................7-11
Electrical System
Add-On Equipment......................................5-95
Fuses and Circuit Breakers...........................5-96
Fusible Links..............................................5-95
Headlamp Wiring.........................................5-95
Instrument Panel Fuse Block.........................5-96
Power Windows and Other Power Options......5-96
Underhood Fuse Block.................................5-99
Windshield Wiper Fuses...............................5-95
Engine
Air Cleaner/Filter.........................................5-38
Alarm and Automatic Shutdown.....................2-18
Change Engine Oil Light...............................3-39
Check and Service Engine Soon Lamp...........3-36
Checks Before Operating..............................2-23
Coolant......................................................5-47
Coolant Heater............................................2-25
Coolant Temperature Gage...........................3-34
Diesel Engine Exhaust Brake........................2-26
Drive Belt Routing......................................5-110
Exhaust.....................................................2-45
Exhaust Restrictor.......................................2-22
Fan Breakage............................................... 5-6
Fan Noise..................................................5-49
High Idle System.........................................2-20
Oil ....................................5-24, 5-27, 5-28, 5-32
Oil Life System...........................5-35, 5-36, 5-38
4

G
Gage
Air Pressure...............................................3-47
Check Gages Warning Light..........................3-43
Engine Coolant Temperature.........................3-34
Filter Minder...............................................3-46
Fuel..........................................................3-44
Hourmeter..................................................3-47
Oil Pressure...............................................3-38
Speedometer..............................................3-25
Tachometer.................................................3-25
Transmission Temperature.............................3-40
Voltmeter Gage...........................................3-30
Gasoline
Octane........................................................ 5-6
Specifications............................................... 5-7
Gasoline Engine, Starting.................................2-12
GM Mobility Reimbursement Program.................. 7-5
H
Hazard Warning Flashers................................... 3-6
Headlamp Wiring............................................5-95
Headlamps
Bulb Replacement.......................................5-71
Daytime Running Lamp................................3-15
Exterior Lamps............................................3-14
High/Low Beam Changer................................ 3-8
On Reminder..............................................3-14Heater...........................................................3-20
Engine Coolant...........................................2-25
High Idle System............................................2-20
Highbeam On Light.........................................3-42
Highway Hypnosis...........................................4-15
Hill and Mountain Roads..................................4-16
Hood
Checking Things Under................................5-22
Latches......................................................5-23
Horn ............................................................... 3-6
Hourmeter Gage.............................................3-47
How to Wear Safety Belts Properly...................1-16
I
Ignition Positions.............................................2-11
Infants and Young Children, Restraints...............1-32
Inflation - Tire Pressure...................................5-77
Instrument Panel
Brightness..................................................3-16
Cluster.......................................................3-24
Overview..................................................... 3-4
Switchbank.................................................3-18
J
Jump Starting.................................................5-62
6