Communication network of modules (Freelander 2)

In the vehicle wiring system, several communication networks of various types have been formed, which serve to transfer commands and information between control modules. The configuration on a particular vehicle depends on the model and on the equipment level.

Onboard communication networks are:

• LIN bus (Local Interconnect Network)
• Medium speed CAN bus
• High speed CAN bus
• Outline Media Oriented System Transport (MOST)

Tire	Transfer rate
LIN bus	9.6 kbps
Medium speed CAN bus	125 kbps
High speed CAN bus	500 kbps
MOST circuit	24 Mbps

LIN bus

LIN bus (Local Interconnect Network) is a low-speed broadcast network, which consists of main and auxiliary (workers) elements. The master element sends a message over a single wire to the work elements, identifying which work element should respond. The message has a title (work item ID) and an empty data field. The identified work item populates the data field with the appropriate information and returns a message to the main item on the same wire.

CAN bus

CAN bus (Controller Area Network) is a high-speed data link over which control modules automatically transmit information every few microseconds. Information is transmitted over a pair of twisted wires known as CAN high and CAN low. Information is transmitted over the CAN bus as a voltage difference between two wires.

The car uses two CAN networks - medium speed and high speed, and CJB acts as a gateway between these two networks. The table given below shows the wire colors used in both networks.

Net	High	Low
Medium speed tire	Gray and orange	Purple and orange
high speed bus	White and blue	White

MOST circuit

MOST circuit (Media Orientated System Transport) uses fiber optic cables to transmit data and audio signals related to the infotainment system. The fiber optic cables are looped and each loop unit has 'MOST in' and 'MOST out' connectors.

The MOST loop is a synchronized network. The network master sets the time, and all other devices on the loop operate according to the clock pulses of this timer. The synchronizing unit for the MOST loop is the integrated control module.

The following precautions must be observed when servicing the MOST fiber optic busbars:

• After disconnecting any wires, carefully install the appropriate dust caps to protect the mating surfaces of the connectors from damage or contamination.
• Do not bend fiber optic wires with a bending radius of less than 25 mm or twist them when performing maintenance or repairs. Sharp kinking or twisting may degrade performance, cause immediate system failure or future failure.
• Avoid applying excessive force and straining or stressing the fiber optic cable or connectors, especially residual stresses after installation.

Checkpoint Diagnostics

In an additional electrical junction box (AJB) built-in RBD link (Ring Break Diagnostics). The RBD link contains a copper jumper that, when removed, initiates testpoint diagnostic mode. The test point diagnostic mode allows the mechanic to locate a break in the MOST loop light guide. To initiate diagnostic mode using a checkpoint, perform the following procedure:

• Connect diagnostic equipment approved by Land Rover.
• Put the car in power mode 4 or higher.
• Remove the RBD jumper within the time interval specified by the Land Rover approved diagnostic system.
• Replace RBD jumper.

After approximately 30 seconds, a DTC will be set in the integrated control module (DTC), which identifies the location of the fault. The DTC is read by a Land Rover approved diagnostic system.