LR3/Disco 3
Longitudinal and lateral acceleration
Engine speed
Engine torque
Oil temperature
Accelerator pedal position
Wheel speed.
Using these signals, additional transmission control can be obtained. The TCM can calculate when the vehicle is
cornering, all wheels are gripping, the driver is braking or if the driver is accelerating. This is the conventional 'Adaptive'
transmission control. ASIS uses this system but adds the continuous adaptation of the gear changes to the individual
driving style of the driver.
HDC Mode
The HDC mode assists the ABS module in controlling the downhill speed of the vehicle. When HDC is selected on, the
ABS module selects the most appropriate gear for the descent, to maximise engine braking.
Cruise Mode
When speed control is activated, the TCM receives a cruise active message on the CAN bus. The TCM activates a speed
control map which prevents locking and unlocking of the torque converter clutch and minimises up and down shifts.
Hill Mode
Hill mode is initiated by the TCM when the engine torque, via ECM signals on the CAN bus, exceeds the theoretical load
curve for normal operation. The TCM monitors this signal to determine when the vehicle is travelling up or down a steep
gradient.
In hill mode the TCM adopts one of four shift maps, three uphill and one downhill. The shift map chosen depends on the
severity of the slope as determined from the engine signals and the appropriate gear is selected to assist with the ascent
or descent.
Hill mode can also be initiated when the vehicle is at very high altitudes or ambient temperatures, and also when the
vehicle is towing.
Default (Limp Home) Mode
If a transmission fault is detected by the TCM, the TCM adopts a limp home mode strategy. 'TRANS. FAILSAFE' is
displayed in the message centre and, if the fault has an effect on engine emissions, the MIL will also be illuminated.
In default mode, P, R and N functions operate normally (if the fault allows these selections) and the TCM locks the
transmission in 3rd or 5th gear to allow the driver to take the vehicle to the nearest dealer. The torque converter lock-up
clutch is disabled and reverse lock-out will not function.
If the vehicle is stopped and subsequently restarted in the default mode condition, the TCM operates normally until the
fault which caused the condition is detected again.
When limp home mode is active, the gear position indicator will show one of the following letters which defines the fault
type:
'F' - transmission is operating in limp home mode
'H' - transmission has reached overheat threshold temperature and transmission is operating in limp home mode
'E' - CAN bus is off and transmission is operating in limp home mode.
If electrical power is lost and the transmission is operating in mechanical limp home mode, the selector lever will not be
locked in the 'N' position by the shift interlock solenoid. The lever will be locked in the 'P' position and can only be
released by using the interlock emergency release lever or by correcting the electrical fault.
Reverse Lock-Out Mode
