This Wiring Diagram Service Manual, Version 2, covers FM Series, FH Series, and NH12 Series trucks produced up to December 2005. It is an essential resource for understanding the complex electrical systems of these robust vehicles, which have been a cornerstone in regional, long-haul, and heavy-haul transportation. The manual provides comprehensive, component-level wiring diagrams, crucial for accurate diagnostics and repair of electrical faults.
This manual is specifically designed to assist dealerships, independent repair shops, fleet maintenance personnel, and experienced mechanics in troubleshooting and maintaining the electrical systems of the specified truck models. It details electrical systems from engine management and powertrain to chassis, cab interior, lighting, and safety features. The manual includes component wiring diagrams, harness illustrations, fuse and relay information, ground connections, and connector details, all presented with high-resolution diagrams and a clear cable color code to ensure precise electrical work.
Wiring diagram
FM
FH
NH12
VERSION2
UPTO > DEC 2005
FM, FH CHID A615020–
FM, FH CHID B421649–
Contents
Example of wiring diagram ................................................................... 2
Component wiring diagram index ........................................................ 5
Component wiring diagrams ................................................................ 8
Illustrations index ................................................................................ 98
Illustrations ........................................................................................... 99
Fuses ................................................................................................... 185
Relays ................................................................................................. 187
Wiring harness illustration index ..................................................... 189
Ground connections .......................................................................... 192
List of ground connections ................................................................. 194
List of connectors .............................................................................. 195
List of components ............................................................................ 204
Abbreviations ..................................................................................... 210
Cable colour code .............................................................................. 212
Wiring diagram
FM
FH
NH12
VERSION2
UPTO > DEC 2005
FM, FH CHID A615020–
FM, FH CHID B421649–
Contents
Example of wiring diagram ................................................................... 2
Component wiring diagram index ........................................................ 5
Component wiring diagrams ................................................................ 8
Illustrations index ................................................................................ 98
Illustrations ........................................................................................... 99
Fuses ................................................................................................... 185
Relays ................................................................................................. 187
Wiring harness illustration index ..................................................... 189
Ground connections .......................................................................... 192
List of ground connections ................................................................. 194
List of connectors .............................................................................. 195
List of components ............................................................................ 204
Abbreviations ..................................................................................... 210
Cable colour code .............................................................................. 212
