Operation
Operation
ABS Braking Mode
The ABS ECU controls the ABS function of the system in two ways:
1 Engine intervention
2 Braking intervention
During brake intervention the ABS ECU energizes the inlet and outlet solenoid valves of the related brake and starts the return pump. The inlet solenoid valve closes to isolate the brake from pressurized fluid; the outlet solenoid valve opens to release pressure from the brake into the expansion chamber end the return pump circuit. The brake releases and the wheel begins to accelerate. The ABS ECU then operates the inlet and outlet valves to control the supply of hydraulic pressure to the brake and apply the maximum braking effort (for the available traction) without locking the wheel.
Dynamic Stability Control (DSC)
The DSC system is designed to improve the lateral stability of the vehicle in all driving situations.
The DSC system is active unless switched off by the DSC switch in the dashboard. When switched off the DSC warning lamp is permanently illuminated.
DSC optimizes dynamic stability, even in critical driving situations. The system controls dynamic stability when accelerating and when starting from a standstill. Additionally, it identifies unstable driving behavior, such as understeering and over-steering, and helps to keep the vehicle under control by manipulating the engine output and applying the brakes at individual wheels. Some noise may be generated when the brakes are applied. The system is ready to operate each time the engine is started.
The indicator lamp in the instrument pack extinguishes shortly after the engine has been started. If the indicator lamp flashes, the system is active, regulating engine output and brake forces. If the lamp does not extinguish after starting the engine, or illuminates continuously during a journey, the system has a fault, or has been de-selected using the switch provided. Without USC, the vehicle may be driven as normal, but at the limit of adhesion its behavior will be less predictable.
If the power supply has been interrupted by disconnecting the vehicle's battery, ABS and DSC will be deactivated. These functions are reactivated by driving a short distance, or by turning the steering wheel from lock to lock while the vehicle is stationary and the engine is running. Reactivation is indicated by extinguishing of the warning lamps.
ETC is continuously available to boost vehicle traction when one or more wheels has a tendency to spin. It operates in conjunction with the DSC system. If a wheel is tending to spin, ETC automatically brakes that wheel until it regains grip and can transmit the engine's power again. This braking activity causes the engine's power to be transferred the remaining wheels. Some noise may be generated when the brake is applied to the spinning wheel.
It is possible to de-select the stability control function of DSC, leaving the ETC system active, by pressing the DSC button. The amber DSC lamp illuminates continuously, to indicate that the stability function is passive. It is recommended that the DSC system should tee temporarily de-selected, in order to maximize forward traction, only in the following exceptional circumstances:
^ If the vehicle needs to be rocked out of a hollow or a soft surface
^ Starting in deep snow, or on a loose surface
^ Driving in deep sand
^ On tracks with deep longitudinal ruts
^ Driving through deep mud
If the DSC button is pressed a second time, the system will be re-selected, and the amber DSC lamp will extinguish.
Electronic Traction Control (ETC)
The ability to control the vehicle while driving, is lost as a result of excessive wheel spin or slip if a type exceeds its ability to:
^ Maintain traction
^ Accept side forces to maintain directional control
The ETC feature of the DSC on the New Range Rover cannot be switched OFF with the DSC switch. Pressing the button will only switch off the dynamic stability control function of the DSC.
The traction control feature is needed at all times to provide anti-wheel spin control especially when driving the vehicle off road. The DSC warning lamp in the instrument cluster will come on when the system is switched off manually or there is a fault in the system.
Off road traction control or HDC operation places an additional load on the brakes. To prevent overheating of the brakes and discs, the temperature of the discs is calculated over time from the road speed and amount of brake application (from the pressure sensor). If the temperature of one or more discs goes above approximately 600°C, the traction control function for that wheel will be cancelled temporarily. Engine intervention is still active to prevent spinning of that wheel. Once the temperature of the disc goes below approximately 500°C, the traction application will be reactivated.
The normal braking function (including ABS) is always active at any temperatures.
Corner Braking Control (CBC)
CBC improves stability control while braking through corners.
As the vehicle enters a comer, the weight of the vehicle shifts to the outside wheels. With non CBC equipped vehicles, if the driver brakes while driving through a corner an equal hydraulic force is applied to each wheel. Though the pressure is equal the grip available for braking is unequal at the type footprint due to the increased weight on the outside wheels.
With a CBC equipped vehicle, the feature regulates the applied pressure to the wheels based on the rate of cornering. When the driver brakes, an unequal hydraulic pressure is applied to each side of the vehicle. Though the brake application pressure to each wheel is unequal, the dynamic of the vehicles weight transfer compensates for the unequal pressure, as a result braking effort is distributed in proportion to the grip available ensuring that lateral grip is maintained.
Electronic Brake Distribution (EBD)
Electronic brake proportioning allows the DSC system to adjust the braking force to the rear wheels based on the vehicles loading to maximize the braking force at all wheels.
The ABS control module monitors the wheel speed sensors inputs when the brakes are applied, for activation of this feature. The control module compares the speed at which the front and rear axles are slowing down to determine vehicle loading.
If the rear axle is slowing at a similar rate to the front, it indicates that the vehicle is loaded and braking force need not be limited to the rear axle.
If the deceleration of the rear axle is greater than the front, the vehicle is lightly laden and less force can be applied to the rear. If the same force were applied, then the vehicle could become unstable.
The values for the relative deceleration are programmed in the ABS ECU. Equal force will be applied to the front and rear axles until the threshold values are exceeded. At this point, the ABS ECU will cycle the inlet valves at the rear calipers to limit or reduce the braking force on the rear axle.
Emergency Brake Assist (EBA)
The EBA is designed to enhance the braking control of the DSC for the driver of the vehicle. The EBA includes two functions that are programmed into the control electronics of the ABS ECU with no additional hardware changes.
The first EBA function is designed to provide the maximum braking force available during rapid (panic) braking situations The ABE control module looks at the inputs from the brake pedal switch and the signal from the brake pressure sensor on the master cylinder. The criteria for activation of EBA is the speed et which brake pressure builds up with the brake pedal depressed. The total criteria required for EBA activation includes:
^ Brake switch ON
^ Brake pressure build up Threshold value
^ Vehicle road speed >5 MPH (8 mph)
^ Vehicle not in reverse
^ Not all wheels in ABS operation
If the threshold for EBA activation is achieved, the ABS control module will activate a pressure build up regulation phase through the hydraulic unit. The pressure at all wheels is increased up to the ABS operation point. This occurs even if the driver does not achieve the ABS operation point with the pedal.
The front and rear axle brakes are controlled individually. ABS operation will continue until the driver releases the pedal and the pressure in the master cylinder drops below the threshold value stored in the ABS ECU.
The second EBA function is also designed to enhance a driver initiated braking procedure. The EBA will build up the pressure in the rear brake circuit when the front brakes are already in an ABS regulation cycle. The additional braking pressure at the rear wheels will shorten the stopping distance. The following criteria must be met before the ABS control module will activate EBA:
^ Both front wheel brakes in ABS operation
^ Vehicle speed >5mph (8km/H)
^ Vehicle not in reverse
^ EBA and pressure sensor initialization test OK
^ Rear wheels not in ABS operation
EBA sensitivity can be adjusted using Test Book/T4. There are three sensitivity settings, default is the most sensitive.
Hill Descent Control (HDC)
Hill Decent Control (HDC) is designed for off road use to automatically slow the vehicle and maintain a steady speed on steep gradients. This function allows the driver to focus on steering and controlling the vehicle without having to use the brakes to slow the vehicle.
HDC is activated manually through the switch located in the center console next to the transmission gear selector. HDC can lee selected under any conditions while low range is selected, and below the 21 mph (35 mph) speed threshold when high range is selected. The HDC Lamp in the instrument pack indicates HDC selection status. If enable conditions are not met, system goes in to stand by mode. When activated, the vehicles speed is held to approximately 5 MPH (3 km/h) by the DSC ECU pulsing the brakes to maintain the speed.
The following conditions must be met before the FBC will activate:
^ HDC switch operated -LED-'ON'
^ Vehicle speed: <21 MPH (35 km/h)
^ Accelerator pedal pressed <15%
^ Downhill driving recognized
If the HDC switch is operated alcove 21 mph (35 mph) in high range, "NO HDC - SLOW DOWN" message will be displayed in the instrument pack, and HDC will not be selected.
If the HDC switch is held down for more than 10 seconds, the HDC selection status does not change If HDC is selected, then vehicle ignition switched off, the HDC selection status remains in the ABS ECU memory for 6 hours. If the vehicle is restarted within this time, HDC remains selected. If vehicle is not started within this time HDC will be automatically de-selected. If the vehicle speed exceeds 37 mph (60 km/h) while high range is selected, HDC is automatically de-selected.
Hill Descent Control Enable Criteria
The target speed used lay the HDC varies in response to driver inputs. Current target speed will lie in the range between Maximum Target Speed and Minimum Target Speed.
Hill Descent Control Target Speeds
When HDC is first activated, if the driver does not press the brake or accelerator pedals, then current target speed is set to default target speed. If HDC is activated and the driver presses the brake pedal, the vehicle brakes operate as normal. While the brake pedal is pressed:
^ If vehicle speed is equal to or more than current target speed, current target speed is unchanged
^ If vehicle speed is less than current target speed, current target speed is set to vehicle speed
When the brake pedal is released:
^ If vehicle speed is equal to or more than minimum target speed, then current target speed is unchanged
^ If vehicle speed is less than minimum target speed, then Current Target Speed is set to minimum target speed.
If HDC is activated and the driver presses the accelerator pedal, current target speed is defined by a characteristic as follows:
^ If current target speed is less then default target speed, then the target speed is set to current speed.
When the accelerator pedal is released:
^ If current target speed is greater than default target speed and vehicle speed is equal to or more than default target speed, then current target speed is set to default target speed
^ If current target speed is more than default target speed and vehicle speed is less than default target speed, then current target speed is set to vehicle speed
^ If current target speed is less then or equal to default target speed, end vehicle speed is less than current target speed, then current target speed is set to vehicle speed
^ If current target speed is less than or equal to default target speed, and vehicle speed is equal to or more than current target speed, then current target speed is unchanged.
To ensure that the vehicle is in an appropriate gear during HDC activity the ABS ECU communicates with the ABS ECU. A unique gearbox map is activated when HDC braking activity begins. The characteristics of the map are that lower gears Preselected sooner then normal, and higher gears are selected later than normal. This reduces the work done by the foundation brakes, and improves the response time of HDC.
Fade-Out Mode
Fade-out and system switch off is triggered by the following:
^ Driver de-selection
^ System failure.
Fade-out and system stand by mode is triggered by the following:
^ Throttle pedal pressed in neutral
^ Brake overheat.
By gradual reduction of brake pressure, the vehicle is allowed to accelerate at a maximum rate of 0.5 m/s3 until maximum target speed is reached, or until no active pressure in system for 0.5 seconds. The system then switches off, or into stand by mode, depending on the trigger for fade-out mode
If the throttle pedal is pressed less than 20% (parameter>, fade-out acceleration limited to - musk. If the throttle pedal is pressed 20% or more, system switches off, or into stand by mode, depending on the trigger for fade-out mode.
Off-Road ABS Control Module Programming
The programming for ABS regulation allows a higher threshold for ABS regulation when driving off-road in loose gravel or dirt. A locked wheel is more effective in slowing or stopping the vehicle because of the wedge that is built up in front of the type.
The programming in the ABS control module allows one or both front wheel(s) to lock up at low speeds on a rough road as long as the vehicle is traveling straight ahead. If the ABS ECU receives a signal from the steering angle sensor indicating a turn, ABS regulation will activate to prevent the lock and allow the vehicle to be steered.