LR3/Disco 3
The transfer box control module is connected on the CAN bus and controls transfer box operation using CAN messages
from other control units on the network. Wheel speed, vehicle acceleration, engine torque and speed, gear information,
from the automatic transmission, temperature information, car configuration, axle ratios and Terrain Response™ mode
inputs, are some of the main signals received by the control module.
In the event of a CAN bus failure the following symptoms may be observed:
Shift from high to low or low to high inoperative
Instrument cluster low range warning lamp inoperative
warning messages or lamps displayed in instrument cluster.
Gear Position Sensor (Manual Transmission Only)
The transfer box control module uses positional information from the manual gear position sensor to determine which
gear the transmission is in. This information is broadcast on the CAN bus for display on the instrument cluster and for use
by other vehicle systems. Vehicles fitted with automatic transmission use a similar message broadcast by the
Transmission Control Module (TCM). Vehicles fitted with manual transmission have a learning function, which compares
the positional information from the sensor with the gear ratio calculated from the ratio of engine speed to transmission
output shaft speed. The transmission learning is carried out at end of manufacture. If a new transmission is fitted during
the life of the vehicle the learning algorithm needs to learn the characteristics of the new transmission.
The instrument cluster displays the selected gear as determined by the transfer box. The transfer box also uses this to
check the vehicle is in neutral before attempting a range change. For additional information, refer to
Manual
Transmission
(308-03 Manual Transmission/Transaxle - 2.7L Diesel)
Manual Transmission Output Shaft Speed Sensor
