- Engine management system (engine control module)
- Gearbox control system (transmission control module - only for vehicles with automatic transmission)
- Transfer case control system (transfer case control module)
- Rear differential control system (rear differential control module - if equipped)
- Air suspension control system (air suspension control unit)
- Brake system (ABS/DSC/ETC/HDC functions) (ABS module).
Each subsystem works differently depending on the selected system program "Terrain Response", providing optimal traction, stability and control of the car when driving on certain terrain. The system has "margin of safety", which guarantees the safe use of any program on any surface, even if the wrong program is selected.
Engine management system (EMS)
The engine management system changes the throttle response to the accelerator pedal and thereby regulates the engine torque. The engine management system can select one of the throttle control programs that provide a different change in torque for the same pedal stroke. Also, the engine management system can vary the throttle response to adjust the allowable change in torque depending on pedal travel.
Each system program "Terrain Response" sets a certain combination of operating parameters of all subsystems. Switching between programs causes a different set of operating parameters to be selected, which is felt by the driver. The driver notices a difference in engine and throttle response. For example, if the accelerator pedal is held in one position and the program switches from "Grass/gravel/snow" per program "Sand", torque and engine speed increase. When switching from a program "Sand" per program "Grass/gravel/snow" the driver will notice a reduction in engine torque and engine speed.
NOTE: Torque and speed change takes approximately 30 seconds. Should not accept system program switching "Terrain Response" for a malfunction of the engine control system.
Automatic transmission control system
The transmission control module changes the shift pattern according to the selected program "Terrain Response". This change results in earlier or later upshifts and downshifts.
When pulling away on a slippery surface, 2nd high gear or 3rd low gear will be engaged to prevent wheel spin. When driving through mud, the gearbox will provide maximum torque. When driving on sand, the gearbox will ensure maximum use of engine power.
When using a special program "Slow motion on rocky terrain" to move away, first gear will be engaged.
The sport mode is only available when the general program and the top gear of the transfer case are selected. The sport mode does not work at the lowest level and when any special program of the system is selected "Terrain Response". CommandShift™ mode is available with any program selected on both the high and low transfer case gears.
If the gearbox is in sport mode and a special program is selected, the gearbox will automatically switch to manual mode "CommandShift™". If a special program has already been selected and the gear selector lever is moved from 'D' to "Sport", the transmission will automatically switch to 'CommandShift™' mode.
Transfer case and rear differential control system
Electronically controlled transfer case differential and electronically controlled rear differential (in the presence of) considered as a single system. An electronically controlled rear differential is optional on vehicles equipped with "Terrain Response". There are two differential control strategies: active and reactive.
An active strategy is to predict the lockup torque required by each differential to minimize slip and maximize stability. Each program "Terrain Response" has different thresholds and criteria for the active strategy. An active strategy improves traction and stability by preventing wheel spin. This is achieved by predicting the required blocking torque for the selected program. For example, more lockout torque is required for driving on rocky or slippery terrain.
When using a reactive strategy, the required torque for locking varies depending on the actual wheel spin and the driving dynamics of the vehicle. Each program "Terrain Response" match certain thresholds and inputs to a reactive strategy. The reactive strategy improves wheel traction and vehicle stability by eliminating wheel slip that persists after the active strategy has been applied.
The torque applied for locking depends on the selected program "Terrain Response". For example, on a slippery road, the least amount of torque is required to provide maximum traction and minimum pavement damage.
Various signals from other subsystems are used to calculate the lockup torque, such as engine torque, throttle position, gear selected, steering angle, vehicle speed, lateral acceleration, and yaw rate.
The ABS dynamic stabilization function has priority over differential control by the system "Terrain Response" and may cause a decrease in the locking torque during its operation. For more information refer to Anti-Lock Control - Traction Control (206-09A Anti-Lock Control - Traction Control).
Air suspension control system
The air suspension control unit provides automatic switching between normal height and off-road height. Height change information is provided via the instrument cluster message center and LED symbols on the switch. The automatic height adjustment of the car provides an increase and decrease in ground clearance, which allows you to get the most out of the selected program "Terrain Response".
On a vehicle with a properly installed and approved Land Rover hitch, the suspension height must not be changed when an electrical load is connected to the hitch. A message appears on the message center display informing you that a trailer is attached to the vehicle and the off-road height cannot be selected automatically. The driver can raise the suspension manually using the air suspension switch.
NOTE: The auto-height lock will only work if the vehicle is equipped with a Land Rover approved hitch and an electrical load is detected at the hitch connector.
Anti-lock braking system
The ABS module controls several vehicle functions and adjusts the parameters of these functions to optimize the selected program "Terrain Response".
The traction control system uses different slip/acceleration thresholds to improve traction and vehicle stability. For example, the sensitivity of the system is increased when driving on a slippery road to reduce wheel spin.
If using a special program "Terrain Response" the dynamic stabilization function is turned off (using the DSC switch on the instrument panel), the next time you select another program, the dynamic stabilization system is automatically turned on again.
The stability control system uses different thresholds for the selected program to reduce its impact and eliminate the need for the driver to turn off the stability control system to reduce engine interference, which is sometimes required in severe off-road conditions. When driving in deep sand, in addition to program selection "Sand" it may be useful to disable the dynamic stabilization function using the DSC switch on the instrument panel.
The Descent Control system turns on and off automatically and the set speed is set according to the selected program "Terrain Response". Also, if necessary, the sensitivity of the controlled descent function is increased.
The Controlled Descent function turns on and off at the optimum times. Hill Descent Control set speeds are also adjusted according to vehicle operating conditions.
Misuse of programs
The driver is informed about the wrong program selection in the following ways:
- The symbol for the selected program flashes continuously in the message center display of the instrument cluster.
- System control unit "Terrain Response" blocks certain functions of some programs, for example: the cruise control function is only available when special programs are turned off or when using the program "Grass/gravel/snow"; the sport mode of the transmission is turned off when using any special program.
- the cruise control function is only available when special programs are turned off or when using the program "Grass/gravel/snow";
- the sport mode of the transmission is turned off when using any special program.
- If any special program is selected except for the program "Grass/gravel/snow", and the ignition is off for more than 6 hours, the system "Terrain Response" disables all special programs by default.
- If a program is selected "Grass/gravel/snow", system "Terrain Response" never goes into default mode and turns off this special program. This feature is intended for use in cold climates where the program needs to be constantly used "Grass/gravel/snow".
- Program "Slow movement on a rocky surface" available only on the lower stage of the transfer case.
Selecting a program that does not correspond to road conditions does not pose a danger to the driver and the car. Continuous use of an inappropriate program may shorten the life of some components. The driver may notice a decrease in the vehicle's dynamic performance due to a deterioration in the response of the engine and transmission compared to a mode in which the special programs are turned off. In addition, in some programs, the controlled descent function remains on, as indicated by the illumination of the HDC indicator on the instrument panel. Also, when driving in some special programs, the driver may notice that the center and rear differentials are locked, causing "braking".
System control unit "Terrain Response" controls the use of special programs of the system, registering the mileage and time of operation of the car according to a special program at the highest and lowest levels. This information can be read by T4 and then used to analyze customer complaints. For example, high fuel consumption may be associated with the constant use of a special program.
Information for the driver
For all vehicles with "Terrain Response" a high-level instrument panel is installed, having a message center for displaying various information. The message center display contains program symbols "Terrain Response", with which the selected program is displayed. If the symbols are not displayed, it means that no special program has been selected and the system is in the mode without special programs.
The driver is also informed of any necessary subsystem status changes via indicators on the instrument panel or appropriate messages on the message center display, for example, the system informs the system about turning off the controlled descent function or changing the height of the air suspension.
Under certain conditions, the system "Terrain Response" can also display tips or warnings to help the driver get the most out of the vehicle, such as:
- The message center display shows the steering angle to help avoid deep ruts with the steering locked.
- Recommended gear displayed when driving on slippery roads
- If the system automatically sets the off-road height and the driver then lowers the suspension to normal height, the system may warn the driver that the vehicle may "sit down" on the bottom.
The messages displayed on the instrument cluster message center display are discussed in detail in section "Information and message center". For more information, please refer to the Information and Message Center (413-08).
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