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Fuse Usage
7 Hazard Warning Flashers
8 Power Post
9 Courtesy Lamps
10 Warning 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 TransmissionFuse Usage
24 Hydraulics/Air Brake
A Spare
B Spare
Fuse Usage
Blank Not Used
BRK Brake Warning Lamp
RT PRK Passenger’s Side Parking Lamps
Blank Not Used
Blank Not Used
LT PARK Driver’s Side Parking Lamps
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
Blank Not Used
PWR WNDW Power Windows
343
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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’s Side Trailer Turn Signal
Blank Not Used
LT TRN TRLR Driver’s Side Trailer Turn Signal
Blank Not Used
Blank Not Used
Blank Not Used
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
NOTE 3L18 Fuel, LG4 Powertrain Control
Valve, LG5 Electronic Control
Module
STUD A Spare
STUD B Spare
Relay Usage
NOTE 1LLY/L18 Fuel Pump Relay, LG4/LG5
Heated Fuel Relay
IGN B Ignition Relay
STARTER Starter Relay
HORN Horn Relay
IGN A Ignition Relay
PTO/ECU*Power Take-Off/Engine Control Unit
(*Diesel 7.8L LG4)
REVERSE Reverse Relay
NEUTRAL
STARTNeutral Start (LG4 Allison Automatic
Transmission Series 3000/3500)
Fuse Usage
IGN 1 Ignition 1
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
346
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H
Hazard Warning Flashers............................ 142
Headlamp Wiring......................................... 341
Headlamps
Bulb Replacement.................................... 315
Daytime Running Lamps.......................... 151
High/Low Beam Changer......................... 144
On Reminder........................................... 150
Heater......................................................... 157
High Idle System......................................... 106
Highbeam On Light..................................... 179
Highway Hypnosis....................................... 229
Hill and Mountain Roads............................. 230
Hood
Checking Things Under............................ 266
Latches.................................................... 267
Horn............................................................ 142
Hourmeter Gage.......................................... 183
How to Use This Manual................................ 4
How to Wear Safety Belts Properly............... 26
Hydraulic Brake Systems............................. 211
I
Ignition Positions........................................... 96
Infants and Young Children, Restraints .......... 45
Inflation - Tire Pressure............................... 322
Instrument Panel
Overview.................................................. 140
Switchbank.............................................. 154
Instrument Panel (I/P)
Brightness................................................ 152
Cluster..................................................... 162
J
Jump Starting.............................................. 305
K
Keyless Entry System................................... 87
Keys............................................................. 86
423