Operating principles (Freelander 2)

The control units of the following vehicle subsystems are used to operate the Terrain Response system:

• Engine Management System - Engine Control Module (ECM)
• Transmission Control System - Transmission Control Module (TCM) (Automatic Transmission Only)
• Active Clutch Control Unit
• Brake system - ABS control unit (anti-lock braking system (ABS)/dynamic stability control (ETC)/electronic traction control (ETC)/hill descent control (HDC))

Each subsystem operates differently, depending on the selected Terrain Response program, to provide optimum traction, stability and vehicle control in given road conditions.

Engine Management System (EMS)

EMS can change the accelerator pedal operation parameters to vary engine torque with the same pedal travel.

Each Terrain Response program uses a combination of operating parameters for each subsystem. Changing programs results in a noticeable change in operating characteristics for the driver, for example: if the accelerator pedal is held in a constant position and the driver changes from Grass/Gravel/Snow to Sand, the driver will notice an increase in torque and engine speed. If the driver changes from Sand to Grass/Gravel/Snow, the driver will notice a decrease in torque and engine speed.

NOTE: It may take approximately 30 seconds for the torque and engine speed to change, so Terrain Response operation should not be mistaken for an EMS malfunction.

Transmission Control System (Automatic Transmission Only)

The transmission control unit changes the gearshift parameters according to the selected Terrain Response program. This results in early or late upshifts or downshifts.

For example, in the Grass/Gravel/Snow program, the transmission will shift up early and down very late. This ensures the highest possible gear. The downhill detection function in the transmission control unit (TCM) will lock the torque converter and, if necessary, hold the selected gear up to the engine speed limit on a steep downhill slope. This ensures maximum engine braking before the driver applies the brakes.

Sport mode is only available when the standard program is selected. Sport mode is not available when any special Terrain Response program is engaged. CommandShift™ mode is available in any program.

Active Clutch Control

The active clutch control unit has two operating strategies: active and reactive.

The anticipatory strategy predicts the amount of locking torque required to minimise slip and improve stability. Each Terrain Response programme has a specific threshold and input criteria for the active strategy. For example, higher locking torque will be used on slippery surfaces.

The reactive strategy changes the amount of locking torque depending on the actual level of slip and the vehicle's dynamic behavior. Each Terrain Response program has a specific threshold value and input criteria for the reactive strategy. The reactive strategy improves wheel traction by preventing wheel slip that occurs after the active strategy is applied. The locking parameters depend on the selected program. For example, high sensitivity on a slippery surface to ensure maximum traction and minimize damage to the surface.



The calculation of the locking torque uses various signals from other subsystems, such as engine torque, accelerator pedal position, gear selected, steering wheel angle, vehicle speed, lateral acceleration, and yaw rate.

The DSC function of the ABS system can adjust the operation of the active clutch control system and reduce the applied locking torque during DSC operation.

ABS system control

The ABS control unit controls several functions and adjusts the operating parameters of these functions to optimize the selected Terrain Response program.

Traction control system

The traction control system uses different slip/acceleration thresholds to improve traction and vehicle stability. For example, to reduce wheel slip when driving on slippery surfaces, the system sensitivity is increased. If slippage is allowed to occur under such conditions, the loss of traction can lead to various consequences: from surface damage (wet grass) to the inability to continue driving due to wheel slippage (snow).

Dynamic Stability Control

If the DSC system is switched off (using the DSC switch next to the Terrain Response rotary control) while using a special Terrain Response program, the DSC system is automatically switched on again when you next switch to another program.

The DSC system uses different threshold values for the selected program to reduce its impact, which eliminates the need for the driver to switch off the Dynamic Stability Control system to reduce engine intervention, which is sometimes required in severe off-road conditions. When driving in deep sand, it may be useful to switch off the Dynamic Stability Control system using the DSC switch, in addition to switching on the Sand program.



In the Mud/Ruts program, the DSC system allows a higher yaw (spin) threshold. This increases the difference between the actual and desired wheel rotation before the Dynamic Stability Control (DSC) intervenes. This allows the DSC system to ignore the influence of the ruts, which manifests itself in a jolt or a change in the steering angle of the front wheels.

Terrain Response can change the balance between engine and brake intervention. For example, when the Sand program is selected, DSC reduces engine intervention and increases brake intervention to maintain the vehicle's torque and prevent bogging down when wheel slip is detected.

[Original article on the web portal: LRman.ru]

Controlled descent system

The descent control mode is switched on and off automatically and the set speed is selected depending on the selected Terrain Response program. The HDC response speed is also increased if necessary.

The automatic operation of the HDC function is designed to assist the driver and is limited to switching the system on or off when it is most needed. HDC is automatically switched on only when the Mud/Ruts program is selected. HDC is not switched on automatically in other programs.