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BRAKE CALIPERS System Operation
When hydraulic pressure is supplied to the caliper, the pistons extend to force the inner pad against the brake disc. The caliper
reacts and slides along two guide pins to bring the outer pad into contact with the brake disc.
BRAKE PAD WEAR SENSORS
When a brake pad incorporating a brake pad wear sensor is approximately 75% worn, the sensor wire within the pad material
is worn through and the brake pad wear sensor goes open circuit. When the instrument cluster detects the open circuit, it
illuminates the amber LED (light emitting diode) in the brake warning indicator, displays an appropriate warning in the
message center and sounds a warning chime.
Refer to: Instrument Cluster (413-01 Instrument Cluster, Description and Operation).
NOTE: A new pad wear sensor lead must be fitted whenever the brake pads are changed, irrespective of the brake pad
warning sensor being triggered.
BRAKE CALIPERS Component Description
Each caliper is mounted within a fixed carrier that is secured to the rear wheel knuckle with two bolts. Each outboard brake pad
is installed with a wire anti-rattle spring.
The brake calipers on SC (supercharger) vehicles are painted and also include a logo badge, secured with two screws, which
must be removed in order to change the brake pads.
The inboard brake pad of the RH (right-hand) brake incorporates a wear sensor.
BRAKE PAD WEAR SENSORS
The brake pad wear sensor is wired in series with a wear sensor on the LH (left-hand) front brake and the instrument cluster. If
the thickness of one of the brake pads connected to a wear sensor decreases to a predetermined limit, the instrument cluster
illuminates the brake warning indicator.
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Braided steel hoses are used to connect the brake pipes to the front and rear brake calipers.
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1 LH (left-hand) front brake 2 RH (right-hand) rear brake 3 LH rear brake 4 RH front brake 5 Primary circuit inlet port 6 Secondary circuit inlet port The ABS module is located in the passenger side, rear engine bay and incorporates the HCU. The HCU is a four channel unit that modulates the supply of hydraulic pressure to the brakes under control of the ABS module.
The primary and secondary outlets of the master cylinder are connected to the primary and secondary circuits within the HCU. The primary circuit in the HCU has separate outlet ports to the RH front and LH rear brakes. The secondary circuit in the HCU has separate outlet ports to the LH front and RH rear brakes.
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6 Pulsation damper 7 Separation valve 8 Damping chambers 9 Separation valve 10 Shuttle valve 11 Hydraulic pumps 12 Motor 13 Shuttle valve 14 Pressure sensor - all vehicles 15 Low pressure accumulator 16 Check valve 17 Low pressure accumulator 18 Inlet valve 19 Inlet valve 20 Inlet valve 21 Inlet valve 22 Outlet valve 23 Outlet valve 24 Outlet valve 25 Outlet valve 26 Pressure sensors - vehicles fitted with adaptive speed control only 27 RH front brake 28 LH rear brake 29 RH rear brake 30 LH front brake www.JagDocs.com
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Hydraulic Brake Actuation - Brake Master Cylinder
Removal and Installation
Removal Published: 11-May-2011
1. WARNING: Make sure to support the vehicle with axle stands.
Raise and support the vehicle.
2. Remove the cowl vent screen.
For additional information, refer to: Cowl Vent Screen (501-02 Front End Body Panels, Removal and Installation).
3. CAUTION: Brake fluid will damage paint finished surfaces. If spilled,
immediately remove the fluid and clean the area with water.
Remove the brake fluid reservoir.
For additional information, refer to: Brake Fluid Reservoir (206-06 Hydraulic Brake Actuation, Removal and Installation).
4. Remove the brake booster vacuum line from the brake vacuum
pump.
5. CAUTION: Make sure that all openings are sealed. Use
new blanking caps.
Disconnect the master cylinder brake pipes.
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Published: 02-Sep-2011
Anti-Lock Control - Stability Assist - Anti-Lock Control - Stability Assist - Component Location
Description and Operation
NOTE: RHD (right-hand drive) installation shown, LHD (left-hand drive) installation similar.
Component Location
Item Description 1 ABS (anti-lock brake system) module 2 RH (right-hand) front wheel speed sensor 3 Instrument cluster 4 Steering angle sensor 5 Yaw rate and lateral acceleration sensor 6 RH rear wheel speed sensor 7 LH (left-hand) rear wheel speed sensor 8 LH front wheel speed sensor
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Press and hold the DSC switch for less than 10 seconds.
The message center will temporarily display either Trac DSC or DSC ON.
The warning indicator in the instrument panel will illuminate while Trac DSC is selected.
The warning indicator will flash when DSC or Trac DSC is active.
NOTE: If cruise control is engaged, it will automatically disengage if DSC activates.
Refer to: Speed Control (310-03 Speed Control - 2.7L V6 - TdV6, Description and Operation).
Corner Brake Control
CBC (corner brake control) influences the brake pressures, below and within DSC and ABS thresholds, to counteract the yawing moment produced when braking in a corner. CBC produces a correction torque by limiting the brake pressure on one side of the
vehicle.
Electronic Brake Force Distribution
EBD (electronic brake force distribution) limits the brake pressure applied to the rear wheels. When the brakes are applied, the
weight of the vehicle transfers forwards, reducing the ability of the rear wheels to transfer braking effort to the road surface.
This may cause the rear wheels to slip and make the vehicle unstable.
EBD uses the ABS braking hardware to automatically optimize the pressure to the rear brakes, below the point where ABS is normally invoked.
NOTE: Only the rear brakes are controlled by the EBD function.
Electronic Traction Control
ETC (electronic traction control) attempts to optimize forward traction by reducing engine torque, or by applying the brake of a
spinning wheel until traction is regained.
ETC is activated if an individual wheel speed is above that of the vehicle reference speed (positive slip) and the brake pedal is
not pressed. The brake is applied to the spinning wheel, allowing the excess torque to be transmitted to the non-spinning
wheel through the drive line. If necessary, the ABS module also sends a high speed CAN bus message to the ECM to request a reduction in engine torque.
When the DSC function is selected off using the DSC switch, the braking and engine torque reduction features are both
disabled, except when the JaguarDrive control is in winter mode. When the JaguarDrive control is in winter mode, selecting the
DSC function off retains the braking and engine torque reduction features, but reduces intervention levels compared to DSC
and Trac DSC modes.
Emergency Brake Assist
EBA (emergency brake assist) assists the driver in emergency braking situations by automatically increasing the applied
braking effort. The ABS module invokes EBA when: The brake pedal is rapidly pressed.
The brake pedal is pressed hard enough to bring the front brakes into ABS operation.
When the brake pedal is rapidly pressed, the ABS module increases the hydraulic pressure to all of the brakes until the threshold for ABS operation is reached. This action applies the maximum braking effort for the available traction. The ABS module monitors for the sudden application of the brakes, using inputs from the brake pedal switch and from the pressure
sensor within the HCU (hydraulic control unit). With the brake pedal pressed, if the rate of increase of hydraulic pressure
exceeds the predetermined limit, the ABS module invokes emergency braking.
When the brake pedal is pressed hard enough to bring the front brakes into ABS operation, the ABS module increases the hydraulic pressure to the rear brakes up to the ABS threshold.
EBA operation continues until the driver releases the brake pedal, sufficiently for the hydraulic pressure in the HCU to drop below a threshold value stored in the ABS module.
Engine Drag-Torque Control
EDC (engine drag-torque control) prevents wheel slip caused by any of the following: A
sudden decrease in engine torque when the accelerator is suddenly released.
A downshift using the Jaguar sequential shift function on automatic transmission vehicles.
When the ABS module detects the onset of wheel slip without the brakes being applied, the ABS module signals the ECM via the high speed CAN bus to request a momentary increase in engine torque.
Understeer Control
Understeer Logic Control is a proactive system which monitors the vehicle for understeer by comparing signals from the yaw
rate and lateral acceleration sensor with signals from the steering angle sensor and wheel speed sensors. www.JagDocs.com
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ABS Module
Item Description 1 LH front brake 2 RH rear brake 3 LH rear brake 4 RH front brake 5 Primary inlet 6 Secondary inlet The ABS module is located in the passenger side, rear engine bay and incorporates the HCU. The module is mounted on the rear face of the HCU, which it uses to control all braking and stability functions by modulating hydraulic pressure to the individual wheel brakes.
Two types of ABS modules are available; one for vehicles with standard Speed Control, one for vehicles fitted with Adaptive Speed Control.
If an ABS modulator fault is detected, 'ABS FAULT' will be displayed in the instrument cluster message center and the amber warning indicator will illuminate.
Refer to: Information and Message Center (413-08 Information and Message Center, Description and Operation).
CAUTION: The ABS module and the HCU comprise a single unit and must not be separated.
Hydraulic Control Unit
The HCU is a four channel unit, secured to a mounting bracket located in the passenger side, rear engine bay. The HCU modulates the supply of hydraulic pressure to the brakes under the control of the ABS module. Refer to: Hydraulic Brake Actuation (206-06 Hydraulic Brake Actuation, Description and Operation).
