Body Control Systems: Description and Operation

Communications Network

Overview

A number of different types of communication network are incorporated into the vehicle wiring harnesses for the transmission of commands and information between control modules.The configuration installed on a particular vehicle depends on the model and equipment level.

The communication networks available on the vehicle are shown in the table below.

NOTE: For ease of reference, all networks are listed in alphabetical order.

NOTE: The Control Diagrams are schematics reflecting communication networks fitted to RHD (right-hand drive) vehicles only.For detailed layouts of the various communications networks fitted to LHD (left-hand drive) and RHD (right-hand drive) vehicles, refer to the Electrical Circuit Diagrams.

AiNET
The Ai Net is an Alpine proprietary network used to communicate between the Rear Seat Entertainment module and the DVD (digital versatile disc) autochanger.

CAN BUS
The CAN (controller area network) bus is a high speed broadcast network where control modules automatically transmit information every few milliseconds.Information is broadcast down a pair of twisted wires, known as CAN (controller area network) high and CAN (controller area network) low.Information is transmitted on the CAN (controller area network) bus as a voltage difference between the 2 wires.

Two CAN (controller area network) networks are used on the vehicle; medium speed and high speed, with the instrument cluster acting as a gateway between the 2 networks.

Both the medium and high speed CAN (controller area network) bus are connected to the instrument cluster and the diagnostic socket.The medium speed CAN (controller area network) bus terminates at the integrated head unit and the immobilization control module.The high speed CAN (controller area network) bus terminates at the parking brake control module and the ABS (anti-lock brake system) control module.

Control modules are connected in a loop or spur configuration.Should a control module that is looped suffer a connector failure, the bus system will separate into 2 sub-busses.Some communication may still be possible within each sub-bus, but symptoms may be noticed by the driver.

DS2 Diagnostic Bus
The DS2 diagnostic bus is a network that indirectly connects a number of communication networks to the diagnostic socket.This allows diagnostic routines to be run using the Land Rover approved diagnostic system.

Diagnostic Socket

The diagnostic socket is connected to all control modules on the bus networks, either directly or indirectly, via the instrument cluster.The diagnostic socket is located in a pocket in the instrument panel, next to the driver's side A pillar.

The majority of control modules connect to the diagnostic socket via the medium and high speed CAN (controller area network) bus networks.

GVIF
The GVIF bus is a Sony proprietary network for the transmission of video between a transmitter device and a display device.In this instance it is used to transmit navigation graphics from the navigation computer to the Touch Screen Display only.

I Bus
The I bus is a Land Rover corporate network connected between control modules of the 'Information and Entertainment' systems.

IS Bus
The IS bus is a dedicated Land Rover corporate network used to transfer information between the rear seat entertainment module and the two rear LCD (liquid crystal display) screens.

K Bus
The K bus is a Land Rover corporate network connected between control modules of the 'body' systems.

LIN Bus
The LIN bus is a low speed broadcast network that employs master and slave components.The master component transmits a message along a single wire to the slave components identifying which slave is to respond.The message has a header (slave identifier) and an empty data field.The identified slave component fills the data field with the relevant information and returns a message to the master component along the same wire.

M BUS
The M bus is a Land Rover corporate network connected between the ATC (automatic temperature control) module and motors on the heater assembly.

MOST RING
The MOST ring uses fiber optic cables to transport data and audio signals around the information and entertainment system.The fiber optic cables are arranged in a ring, with each unit on the ring having a 'MOST in' and 'MOST out' connection.

The MOST ring is a synchronous network.A timing master supplies the clock and all other components on the ring synchronize their operation to this clock.The timing master for the MOST ring is the integrated head unit.

When handling MOST fiber optic cables the following precautions should be observed:
^ After disconnection of any cables carefully install appropriate dust caps to protect the mating faces of the connectors from damage and contamination.
^ Avoid introducing bends of less than 25 mm (0.98 inches) radius or kinks into the fibre optic cable during service or repair.Tight bends or kinks could impair operation, cause immediate system failure, or future system failure.
^ Avoid excessive force, strain or stress on the fibers or connectors especially permanent stress after reinstallation.

P Bus
The P bus is a Land Rover corporate network connected between the GEM (generic electronic module) and 'peripheral' control modules.

SPDIF
The SPDIF is an digital optical network connected between the DVD (digital versatile disc) autochanger and the audio amplifier and is used to output the audio from the DVD (digital versatile disc) autochanger to the audio amplifier.

Control Diagram - AiNET

Control Diagram - Medium Speed CAN Bus

NOTE: Terminating resistors for the medium speed CAN (controller area network) bus are located in the integrated head unit and the immobilization control module

Control Diagram - High Speed CAN Bus

NOTE: Terminating resistors for the high speed CAN (controller area network) bus are located in the ABS (anti-lock brake system) module and the parking brake control module.

Control Diagram - DS2 Diagnostic Bus