The principle of operation of the system (Discovery 3)

ABS

ABS (anti-lock braking system) adjusts the speed of all working wheels to ensure optimum wheel slip when braking at the limit of traction. This prevents wheel locking and helps maintain the vehicle's steering efficiency.

On the front axle, the brake pressure is regulated separately for each wheel. On the rear axle, the brake pressure is modulated by a regulator. The regulator supplies equal pressure to both rear brakes, the level of which is determined by the wheel with the worst grip on the road. This ensures the stability of the rear axle on roads with uneven surfaces.

ARM

The ARM feature uses the brakes and engine to stabilize the vehicle during abrupt maneuvers that could result in a rollover.

ABS module (anti-lock braking system) monitors the driver's actions and the vehicle's behavior based on various signals received from the powertrain, wheel speed sensors, steering angle sensor, and yaw rate and lateral acceleration sensor. This data is compared with the model behavior and, if the vehicle's behavior is recognized as dangerous, the ABS module (anti-lock braking system) reduces engine power or applies the brakes to one or more wheels to stabilize the vehicle and allow the driver to regain control.

When the ignition is on, the ARM function is always active, even if the DSC function is off.

CBC

CBC regulates the pressure in the brake mechanisms until the DSC and ABS threshold levels are exceeded (anti-lock braking system), counteracting the yaw moment that occurs when braking in a turn. CBC creates a corrective torque by limiting the brake pressure on one side of the car.

DSC

DSC controls the brakes and powertrain to maintain lateral stability of the vehicle. When the ignition is on, DSC is always on unless it is switched off using the DSC switch. Even when DSC is off, vehicle maneuvers involving excessive yaw or lateral acceleration may cause the function to be switched on to maintain vehicle stability.

DSC increases safety during sharp maneuvers and during understeer or oversteer that may occur when cornering. ABS module (anti-lock braking system) monitors the vehicle's yaw rate, lateral acceleration and steering input, and based on this data selectively applies individual brakes and transmits signals to adjust powertrain torque to reduce understeer or oversteer.

In general, when understeering, the inside wheels are braked to counteract the yaw motion toward the outside of the turn.; during oversteer, the outside wheels are braked to prevent the rear of the car from moving to the outside of the turn.

ABS module (anti-lock braking system) controls the vehicle's directional stability using signals from the wheel speed sensors, steering wheel angle sensor, and yaw and lateral acceleration sensor. The directional stability is compared with the stored set values and, if the directional stability deviates from the set value, the ABS module (anti-lock braking system) intervenes in the operation of the braking system and applies the appropriate brakes. On vehicles with an automatic transmission, when the DSC function is operating, the ABS module (anti-lock braking system) also transmits signals to the TCM (transmission control module) to prevent gear shifting. If necessary, the ABS module (anti-lock braking system) also transmits signals to the following modules:

• ECM (engine control module) to reduce engine torque
• Transfer case control module for changing the moment of locking of the central differential.
• Rear differential control unit for changing the rear differential locking moment.

The DSC function has priority over the differential lock moment setting requests from the system. "terrain response".

EBD

EBD (electronic Brakeforce Distribution) limits the pressure in the brake mechanisms of the rear wheels. When the brakes are applied, the mass of the car shifts forward, which reduces the braking efficiency of the rear wheels. This can cause the rear wheels to slip and the car to lose stability.

EBD (electronic Brakeforce Distribution) uses ABS components to automatically optimize rear brake pressure before ABS is engaged. EBD (electronic Brakeforce Distribution) controls only the rear axle brakes.

ETC

ETC attempts to optimize traction by reducing engine torque or braking the slipping wheels until traction is restored.

ETC is activated when the speed of an individual wheel exceeds the vehicle's reference speed. (positive slip), and the brake pedal is not pressed. The slipping wheel is braked, which allows excess torque to be transmitted through the drive shafts to the wheels that are not slipping. If necessary, the ABS module (anti-lock braking system) also transmits via high-speed CAN bus (controller network) signal to ECM (engine control module) to reduce engine torque. A request to reduce torque may involve a fast or slow response: a slow response requests a reduction in the throttle opening angle (only for 4.0L and 4.4L); in case of a quick response, the ignition is requested to be turned off (4.0 l and 4.4 l) or fuel supply failure (2.7L diesel engine).



When the DSC function is turned off using the DSC switch, the torque reduction function does not operate.

On vehicles with automatic transmission, during operation of the ETC function, the ABS module (anti-lock braking system) also transmits signals to the TCM (transmission control module) to prevent gear shifting.

EBA

EBA (emergency braking assistance system) helps perform emergency braking by automatically applying maximum braking force. There are two situations in which the ABS module (anti-lock braking system) includes EBA (emergency braking assistance system): when the brake pedal is pressed very sharply and when the brake pedal is pressed with enough force to activate the ABS (anti-lock braking system) for front brakes.

When the brake pedal is pressed sharply, the ABS module (anti-lock braking system) increases the hydraulic pressure in all brake mechanisms until it reaches the ABS activation threshold (anti-lock braking system), providing maximum braking force under current road grip conditions. ABS module (anti-lock braking system) controls the abrupt application of the brakes based on signals from the brake light switch and the pressure sensor in the HCU unit (hydraulic control unit). If the rate of increase of hydraulic pressure exceeds a set threshold when the brake is applied, the ABS module (anti-lock braking system) initiates emergency braking.

If the brake pedal is pressed with enough force to activate the ABS (anti-lock braking system) for front brakes, ABS module (anti-lock braking system) increases the hydraulic pressure of the rear brakes to the level at which ABS is activated (anti-lock braking system).



EBA (emergency braking assistance system) operates until the driver releases the brake pedal enough to release the hydraulic pressure in the HCU (hydraulic control unit) has not fallen below the threshold level stored in the ABS module (anti-lock braking system).

EDC

EDC prevents wheel slippage caused by any of the following:

• A sudden increase in engine torque when the accelerator pedal is pressed sharply.
• Abrupt clutch engagement after downshifting on vehicles with manual transmission.
• Downshifting with CommandShift™ on vehicles with automatic transmission.

If the ABS module (anti-lock braking system) detects the start of wheel slip without applying the brakes, it transmits to the ECM (engine control module) high-speed CAN bus signal (controller network) with a request for a short-term increase in engine torque.

HDC

HDC uses the vehicle's braking system to vary the vehicle's speed and acceleration when driving downhill at low speeds and when driving in off-road or low-traction conditions. Generally, equal pressure is applied to all four brakes, but the pressure of individual brakes can be modified by the ABS function. (anti-lock braking system) and DSC to maintain vehicle stability. The HDC function is selected using the HDC switch on the center console. HDC operates in both high and low gears at vehicle speeds of up to 50 kph.

On vehicles with manual transmission, HDC can only be used in first and high-range reverse gears and in all low-range gears. Once the vehicle has started moving, the clutch pedal must be fully released. Do not operate the vehicle with HDC engaged when the transmission is in neutral.



On vehicles with an automatic transmission, HDC can be used in the high-range D, R, and CommandShift 1 positions and the low-range D, R, and all CommandShift gears. In the D position, the transmission control module automatically selects the most appropriate gear. Do not operate the vehicle with HDC engaged when the transmission is in neutral.

The HDC function can be selected at speeds up to 80 km/h, but it only activates at speeds below 50 km/h. If the HDC function is selected:

• At speeds up to 50 km/h, the HDC status indicator lamp lights continuously if a valid gear is selected and, on vehicles with a manual transmission, the clutch pedal is depressed.
• At speeds between 50 and 80 km/h (31 mph) the HDC status indicator flashes and, on models with a high-level instrument cluster, the message center display shows information that the speed is too high. For more information, refer to Information and Message Center (413-08 Information and Message Center). If the HDC switch is pressed when the vehicle speed is over 80 km/h, the HDC status indicator lamp will not light and the HDC function will not be selected.
• When the speed reaches 80 km/h or more, a warning sound sounds and the HDC function is turned off. At the same time, the status indicator lamp goes out and, on vehicles with a high-level instrument cluster, the instrument cluster message center display indicates that the HDC function has been turned off.

When the HDC function is enabled, the ABS module (anti-lock braking system) calculates the set speed and compares it with the actual speed of the vehicle. The ABS module then (anti-lock braking system) controls the HCU unit (hydraulic control unit) in active braking mode, maintaining the set speed. During active braking, as a result of the HDC function, the ABS module (anti-lock braking system) it also supplies power to the HDC relay to turn on the brake lights. When pressing the brake pedal during active braking, you may feel a pulsation in the pedal, but this does not indicate a malfunction.



The set speed varies from minimum to maximum for each gear and stage, depending on the pedal pressure of the driver. If the driver does not press the pedals, the ABS module (anti-lock braking system) sets the default speed.

Set speed for the lower stage

Limit value	Speed, km/h
	Broadcast
	Automatic transmission		Manual transmission
	1, R	D, from 2 to 6	1, R	from 2 to 6
By default	3,5 (2,19)	6 (3,75)	3,5 (2,19)	6 (3,75)
Minimum	3,5 (2,19)	3,5 (2,19)	3,5 (2,19)	3,5 (2,19)
To Maxim	20 (12,5)	20 (12,5)	20 (12,5)	20 (12,5)

Set speed for the highest stage

Limit value	Speed, km/h
	Broadcast
	Automatic transmission		Manual transmission
	1, R	D	1, R
By default	6 (3,75)	10 (6,25)	6 (3,75)
Minimum	6 (3,75)	6 (3,75)	6 (3,75)
Maxim M	20 (12,5)	20 (12,5)	20 (12,5)

The set speed varies from a minimum to a maximum value depending on the pressure on the accelerator pedal.

The set speed can also be changed using the '+' and '-' buttons of the cruise control system. (if available). For more information, refer to Speed Control (310-03A). For more information, refer to Speed Control (310-03B).

When the set speed changes, the ABS module (anti-lock braking system) limits deceleration and acceleration to values of -0.5 m/s² and +0.5 m/s² respectively.

On models with a manual transmission, the change in the set speed is suspended during gear changes to avoid unwanted braking when releasing the accelerator pedal to change gear. ABS module (anti-lock braking system) determines gear shifting based on the following data:

• Information about the selected gear transmitted via the high-speed CAN bus (controller network).
• Accelerator pedal release speed.
• Clutch pedal condition.

To ensure a safe transition from active braking mode to brake release, the ABS module (anti-lock braking system) uses a soft release strategy, gradually releasing braking force if any of the following conditions are detected during active braking:

• The HDC function is turned off using the HDC switch.
• A failure of a component used by HDC that is not critical to the soft shutdown function.
• Pressing the accelerator pedal when the transmission is in neutral.
• Overheating of brake mechanisms.

If soft shutdown is initiated as a result of a function shutdown or a component failure, the HDC function is disabled by the ABS module. (anti-lock braking system). If soft shutdown is initiated by pressing the accelerator pedal when the transmission is in neutral or by overheating the brakes, the HDC function remains in standby mode and resumes operation when the accelerator pedal is released or the brakes cool.

The soft-off strategy increases the set speed with a constant acceleration of 0.5 m/s², until the maximum set speed is reached or until active braking is required for 0.5 s. If the accelerator pedal is in the range that affects the set speed, acceleration increases to 1.0 m/s².

If soft shutdown is initiated due to a component failure, a warning tone sounds and the HDC status indicator lamp goes out. The HDC fault indicator lamp comes on. (for models with low level instrument cluster), or a fault message is displayed on the message center display. (for models with high-level instrument cluster).

If fade-out is initiated due to brake overheating on a vehicle with a high-level instrument cluster, a message indicating temporary unavailability of the HDC function is displayed. On vehicles with a low-level instrument cluster, the HDC malfunction indicator lamp flashes. When fade-out is complete, the HDC status indicator lamp flashes. The indicators continue to flash and/or the message remains displayed as long as HDC is selected until the brakes have cooled.

To control overheating of brake mechanisms, the ABS module (anti-lock braking system) monitors the duration of the brake engagement and, based on this, calculates the temperature of each brake mechanism. If the calculated temperature of any brake mechanism exceeds a specified value, the ABS module (anti-lock braking system) initiates a soft shutdown. At the end of the soft shutdown cycle, the HDC function is reactivated when the ABS module (anti-lock braking system) determines that the temperature of all brake mechanisms does not exceed 64% of the limit value.