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Headlamp Wiring
The headlamp wiring is protected by a circuit breaker in
the light switch. An electrical overload will cause the
lights to go on and off, or in some cases to remain off. If
this happens, have your headlamp wiring checked
right away.
Windshield Wiper Fuses
The windshield wiper motor is protected by a circuit
breaker inside the motor and a circuit breaker or fuse in
the fuse block. If the motor overheats, the wipers will
stop until the motor cools. If the overload is caused by
an electrical problem, be sure to get it fixed.
Fusible Links
A fusible link is a short piece of wire several gauge
sizes smaller than the circuit it protects. It will melt in an
overload situation, opening the circuit.
Your starter and other circuits have these fusible links.
The size is printed on the insulation. If the insulation
is burned beyond recognition, consult your GM dealer
for the proper size. Replace a fusible link with one of the
same size and insulation type. Fusible link insulation
is a special purpose high-temperature material.The hydraulic brake booster motor feed circuit and
starter circuit are protected by a fusible link. Vehicles
with a diesel engine have a fusible link for the intake
heater feed circuit.
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 your 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.
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Instrument Panel Fuse Block
There are two instrument panel fuse blocks located behind the instrument panel on the passenger’s 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.
Circuit Breaker Usage
1 Stoplamps
2 Center High-Mounted Stoplamp
3 Parking Lamps
4 Powertrain Control ModuleCircuit Breaker Usage
5 Auxiliary Wiring
6 Heater/Air Conditioning
7 Hazard Warning Flashers
8 Power Post
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Circuit Breaker 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
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 SpareFuse Usage
HTD/MIRR Heated Mirrors
Blank Not Used
RT TRN TRLR Passenger’s Side Trailer Turn Signal
Blank Not Used
LT TRN TRLR Driver’s Side Trailer Turn Signal
Blank Not Used
BRK Brake Warning Lamp
RT PRK Passenger’s Side Parking Lamps
Blank Not Used
Blank Not Used
Blank Not Used
LT PARK Driver’s Side Parking Lamps
Blank Not Used
RT REAR
TRN/STOPPassenger’s Side Rear Turn
Signal/Stoplamp
LT REAR
TRN/STOPDriver’s Side Rear Turn
Signal/Stoplamp
RADIO Radio
Blank Not Used
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Fuse Usage
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 Stop Lamp
MRK LTS Sidemarker and Clearance Lamps
Underhood Fuse Block
When a circuit goes out, the problem could be in either
the primary or secondary underhood fuse blocks.
These blocks use blade-type fuses.
Both underhood fuse blocks are located in the engine
compartment, on the passenger’s side of the vehicle.
To access the fuse blocks, gently squeeze both sides of
the cover to unlatch the tabs at the top. Then, unsnap
both attachments at the bottom and remove the cover.
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.
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Fuse Usage
RR DEFOG Rear Defog
ENG 1 Engine 1
ENG 3 Engine 3
PCM-B Powertrain Control Module
BLANK Not Used
Fuse Usage
ENG 4 Engine 4
ENG 2 Engine 2
HTD FUEL Heated Fuel
BLANK Not Used
BLANK Not Used
02A Emissions
A/C COMP Air Conditioning Compressor
ABS 1 Anti-lock Brake System 1
ABS 2 Anti-lock Brake System 2
ABS 3 Anti-lock Brake System 3
ENGINE Engine
E/A PUMP Electronic/Automatic Pump
HORN Horn
NOTE 2L18 Fuel, LG4 Powertrain Control
Valve, LG5 Electronic Control
Module
NOTE 3L18 Fuel, LG4 Powertrain Control
Valve, LG5 Electronic Control
Module
STUD A Spare
STUD B Spare Primary Underhood Fuse Block
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Relay Usage
NOTE 1LG4 Powertrain Control Valve,
L18 Fuel Pump, LG5 Heated Fuel
IGN B Ignition
STARTER Starter
HORN Horn
IGN A Ignition
PTO/ECU*Power Take-Off/Engine Control Unit
*Diesel 7.8L DURAMAX
®
REVERSE Reverse
NEUTRAL
STARTNeutral Start
Fuse Usage
IGN 1 Four-Wheel Drive Module
IGN 4 Ignition 4
IGN 3 Ignition 3
BATT/HAZ Battery/Hazard Warning Flashers
HEADLAMP Headlamps
LIGHTING Interior/Exterior Lamps
HVAC Climate Control System
NOTEC4/C5 Electric Brake,
C6/C7/C8 Brake Lamps Secondary Underhood
Fuse Block
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