2010 JAGUAR XFR power steering

Published: 11-May-2011
Anti-Lock Control - Stability Assist - Anti-Lock Control - Stability Assist - Overview
Description and Operation

Overview

The ABS (anti-lock brake system) and DSC (dynamic stability control) system features a Bosch modulator, which is an
integrated four-channel HCU (hydraulic control unit) and ABS module. The unit is located in the rear of the engine compartment on the passenger side, and is installed in the brake hydraulic circuit between the brake master cylinder and the four brake
calipers.

The ABS module is connected to the high speed CAN (controller area network) bus, and actively interacts with other vehicle system control modules and associated sensors to receive and transmit current vehicle operating information.

When required, the ABS module will actively intervene and operate the HCU during braking or vehicle maneuvers to correct the vehicle attitude, stability, traction or speed. During incidents of vehicle correction, the ABS module may also request the ECM (engine control module) to control engine power in order to further stabilize and correct the vehicle.
To provide full system functionality, the ABS and DSC system comprise the following components: DSC switch.
Four wheel speed sensors.
Steering angle sensor.
Yaw rate and lateral acceleration sensor.
Stoplamp switch.
Instrument cluster indicator lamps.
Integrated ABS module and HCU. Brake booster vacuum sensor (3.0L vehicles only).

Two variants of ABS module are available, Bosch ESP®8.1 and Bosch ESP®plus8.1. The Bosch ESP®plus8.1 system is fitted to vehicles with ACC (adaptive cruise control) and incorporates a new feature to Jaguar known as 'electronic brake prefill'.

Electronic brake prefill, senses any rapid throttle lift off, activating a small brake hydraulic pressure build-up of approximately 3
to 5 bar (43.5 to 72.5 lbf/in²) in anticipation of the brakes being applied. This application produces a quicker brake pedal
response and consequently slightly shorter stopping distances. When the ECM detects rapid throttle lift off it signals the ABS module which controls the HCU to apply a low brake pressure to assist in a quicker brake application.

NOTE: All vehicles with ACC are supported by the Bosch ESP®plus8.1 system.

The ABS provides the following brake functions that are designed to assist the vehicle or aid the driver: ABS. DSC, including Trac DSC.
CBC (corner brake control).
EBD (electronic brake force distribution).
ETC (electronic traction control).
EBA (emergency brake assist).
EDC (engine drag-torque control).
Understeer control.
Electronic brake prefill (vehicles with ACC only).
Brake vacuum assist (3.0L vehicles only).

All the brake functions listed are automatically active when the ignition is in power mode and the engine is running. The DSC
system can be selected to off using the DSC switch.


WARNING: Although the vehicle is fitted with DSC, it remains the drivers responsibility to drive safely according to the
prevailing conditions.

7 Brake fluid level switch 8 LH rear wheel speed sensor 9 RH rear wheel speed sensor 10 RJB (rear junction box) 11 High mounted stop lamp 12 LH stop lamp 13 RH stop lamp 14 Diagnostic socket 15 TCM (transmission control module) 16 Electronic parking brake module 17 ECM (engine control module) 18 Instrument cluster 19 ABS (anti-lock brake system) module 20 JaguarDrive selector module 21 Adaptive damping control module 22 Adaptive speed control module 23 Yaw rate and lateral acceleration sensor 24 Roof opening panel motor/module 25 Brake booster vacuum sensor (3.0L vehicles only) 26 Steering angle sensor


Anti-Lock Brake System System Operation

ABS controls the speed of all road wheels to ensure optimum wheel slip when braking at the adhesion limit. The wheels are prevented from locking to retain effective steering control of the vehicle.

The brake pressures are modulated separately for each wheel. Rear brake pressures are controlled to maintain rear stability on
split friction surfaces.

Dynamic Stability Control

DSC (dynamic stability control) uses brakes and powertrain torque control to assist in maintaining the yaw stability of the
vehicle. While the ignition is energized the DSC function is permanently enabled, unless selected off using the DSC switch.

DSC enhances driving safety in abrupt maneuvers and in under-steer or over-steer situations that may occur in a bend. The
ABS module monitors the yaw rate and lateral acceleration of the vehicle, steering input and individual wheel speeds, then selectively applies individual brakes and signals for powertrain torque adjustments to reduce under-steer or over-steer
conditions.
In general:

In an under-steer situation the inner wheels are braked to counteract the yaw movement towards the outer edge of the
bend.
In an over-steer situation the outer wheels are braked to prevent the rear end of the vehicle from pushing towards the
outer edge of the bend.

The ABS module monitors the tracking stability of the vehicle using inputs from the wheel speed sensors, the steering angle sensor, and the yaw rate and lateral acceleration sensor. The tracking stability is compared with stored target data. Whenever
the tracking stability deviates from the target data, the ABS module intervenes by applying the appropriate control strategy. The following interactions occur in an intervention situation:

High speed CAN signal to the ECM, to reduce engine torque. Application of braking to the appropriate corner of the vehicle.
Trac DSC

TracDSC is an alternative setting of DSC with reduced system interventions. With TracDSC engaged, traction may be somewhat
increased, although stability may be reduced compared to normal DSC. TracDSC is intended for use only on dry tarmac, by
suitably experienced drivers and should not be selected for other surfaces or by drivers with insufficient skill and training to
operate the vehicle safely with the TracDSC function engaged.

The less restrictive TracDSC setting may be preferred, for example, by expert drivers engaged in high performance driving on
dry Tarmac surfaces such as tracks and circuits.
Switching between DSC and Trac DSC:

beams change state. The LEDs and detectors are mounted in such a way that only one beam will change state, either to broken or restored, at any one time.

The center (straight ahead) position of the steering wheel has to be learned by the ABS module every time the ignition is switched ON. The steering angle sensor is unable to determine the center position so inputs from the yaw rate and lateral
acceleration sensor and wheel speed signals are also used by the ABS module to help it perform this process. If extreme weather conditions are present, for example ice causing extreme wheel spin or understeer/oversteer, the ABS module may not be able to determine the center position of the steering wheel. In this situation 'DSC NOT AVAILABLE' 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).

'DSC NOT AVAILABLE' will also be displayed if the ABS module detects a steering angle sensor fault. The amber warning indicator will illuminate until the fault is rectified.

Yaw Rate and Lateral Acceleration Sensor



The yaw rate and lateral acceleration sensor is mounted on the rear parcel shelf. The sensor is secured by two screws and
connects to the vehicle wiring via a four pin multiplug.

When the ignition is ON, the sensor receives a power feed from the CJB. The ground path for the sensor is located behind the left hand rear seat back. The sensor measures the yaw rate and lateral acceleration of the vehicle, providing values to the ABS module via a dedicated, private high speed CAN bus connection. The ABS module broadcasts these values on the high speed CAN bus for use by other systems.
If a sensor fault is detected by the ABS module, 'DSC NOT AVAILABLE' 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).

Free play (measured at the steering wheel rim) 0-6 0-0.24 Power Steering Pump Specifications
Item Specification Power steering pump relief pressure 106-114 bar Lubricants, Fluids, Sealers and Adhesives
Item Specification Power steering fluid Dexron 3

Steering System - General Information - Steering System
Diagnosis and Testing

Principle of Operation Published: 11-May-2011

For a detailed description of the steering system operation, refer to the relevant Description and Operation sections of the
workshop manual. REFER to:

Power Steering (211-02 Power Steering, Description and Operation), Power Steering (211-02 Power Steering, Description and Operation), Power Steering (211-02 Power Steering, Description and Operation), Steering Linkage (211-03 Steering Linkage, Description and Operation), Steering Linkage (211-03 Steering Linkage, Description and Operation), Steering Linkage (211-03 Steering Linkage, Description and Operation), Steering Column (211-04 Steering Column, Description and Operation), Steering Column (211-04 Steering Column, Description and Operation), Steering Column (211-04 Steering Column, Description and Operation), Steering Column Switches (211-05 Steering Column Switches, Description and Operation), Steering Column Switches (211-05 Steering Column Switches, Description and Operation), Steering Column Switches (211-05 Steering Column Switches, Description and Operation).
Inspection and Verification

1. Verify the customer concern.

2. Visually inspect for obvious signs of damage and system integrity.

Visual Inspection
Mechanical Electrical
Tire condition/pressure
Fluid level
Leaks
Security, condition and correct installation of suspension components
Security, condition and correct installation of steering system components
Fuses
Harnesses for damage/corrosion
Electrical connector(s)
Damaged/corroded pins
CAUTION: If a steering gear assembly is returned under warranty with leaking output shaft seals, but there is also
damage to the steering gear boot/boots the steering gear warranty will be invalid. This is due to the steering gear output
shaft seals being damaged due to foreign materials entering the steering gear boot and damaging the steering gear output
shaft seals thereafter.

3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to
the next step.
4. If the concern is not visually evident, verify the symptom and refer to the symptom chart.

Symptom Charts


WARNING: It is not possible to CHECK the torque of a patchlock bolt, if the torque is suspected to be low, the bolt must
be REMOVED/DISCARDED and a new bolt MUST be INSTALLED and torque to the correct value.


NOTE: If the module or a component is suspect and the vehicle remains under manufacturer warranty, refer to the
Warranty Policy and Procedures manual (section B1.2), or determine if any prior approval programme is in operation, prior to
the installation of a new module/component.

Fluid Leakage


NOTE: Confirm the location of the fluid leak. CLEAN the area of the leak, inspect the area and confirm the exact position.
Ensure the fluid is not from another system on the vehicle.

Symptom Possible Causes Action

Power steering
fluid leakage
Overfilled system
Correct the fluid level as required
Steering gear
Check and install new steering gear as required, refer to the new
module/component installation note at the top of the Symptom
Charts

Symptom Possible Causes Action
Damaged fluid
cap/reservoir
Check and install a new fluid cap/reservoir as required

Loose or damaged
hoses and fittings
O-ring or Dowty seals
Tighten the hose connection or latch plate fixing to the
recommended torque.
REFER to: Specifications (211-00 Steering System - General Information, Specifications).
Check and install new components as required
Install new O-ring or Dowty seals as required
Fluid cooler
Check and install a new fluid cooler as required, refer to the new
module/component installation note at the top of the Symptom
Charts
Power steering pump
Check and install a new power steering pump as required, refer to
the new module/component installation note at the top of the
Symptom Charts Functional

Symptom Possible Causes Action

Steering wheel
misalignment

Steering not correctly centred
Check the steering alignment.
REFER to: Specifications (204-00 Suspension System - General
Information, Specifications).


















Excessive free play at
steering wheel (refer to
the Steering Linkage
Inspection and Backlash
(Free play) Check in this
section)

Steering wheel loose
Check and tighten the steering
wheel retaining bolt as required.
REFER to: Specifications (211-00 Steering System - General
Information, Specifications).
Excess play in the steering linkage
Check and install new
components as required



Steering gear not correctly adjusted (causing
excessive backlash)
CAUTION: DO NOT attempt to
adjust the steering gear yoke. Failure to
follow this instruction will invalidate the
steering gear warranty

Check and install a new steering
gear as required, refer to the
new module/component
installation note at the top of
the Symptom Charts

Lower steering column universal joint pinch
bolts loose
Check and tighten the lower
steering column pinch bolts as
required.
REFER to: Specifications (211-00 Steering System - General
Information, Specifications).

Excessive wear in steering column universal
joints
Check and install a new steering
column or steering column lower
shaft as required, refer to the
new module/component
installation note at the top of
the Symptom Charts

Steering gear mounting bolts loose or
damaged
Check/tighten and install new
steering gear mounting bolts as
required.
REFER to: Specifications (211-00 Steering System - General
Information, Specifications). www.JagDocs.com

Noise

Symptom Possible Causes Action











Continuous noise

Low power steering fluid level
Check for leaks and rectify as required. For further
information refer to the symptom charts for
leakage in this section. Fill power steering fluid
reservoir to correct level
NOTE: Look for small air bubbles
visible in the fluid, air may also get
trapped in the hydraulic system

Air in hydraulic system
Bleed the power steering system.
REFER to: Power Steering System Bleeding (211-00 Steering System - General Information,
General Procedures).
Power steering pipe/hose in
contact with the vehicle body
Check and reposition, or install new IF
damaged/deformed, power steering pipe/hose
Power steering pipe/hose
restricted or twisted
Check and clear restriction to pipe/hose
Reposition power steering pipe/hose. Install new
pipe/hose IF permanently damaged/deformed

Power steering pump mounting
bolts loose
Tighten the power steering pump mounting bolts
to the correct torque.
REFER to: Specifications (211-00 Steering System - General Information, Specifications).


Noise gets worse
when system is
loaded

NOTE: Refer to the power
steering pressure check in this section

Low power steering fluid level
Aerated fluid
Low power steering pump
pressure
Check and fill power steering fluid reservoir to
correct level
Bleed the power steering system.
REFER to: Power Steering System Bleeding (211-00 Steering System - General Information,
General Procedures).
Check power steering pump pressure. If the pump
pressure is low, install a new power steering
pump
Front End Accessory
Drive (FEAD) belt
squeal
FEAD belt incorrectly tensioned
or glazed
Check FEAD belt tension
Check FEAD belt condition and install a new belt
as required
Chirp noise from the
steering pump when a
load is applied
Loose or worn FEAD belt
Check FEAD belt tension
Check FEAD belt condition and install a new belt
as required
Scrape/grind noise
from behind steering
wheel while steering
Steering column shroud foul
condition or clockspring
Correctly install the steering column shroud to
eliminate the foul condition
Install a new clockspring as required
Foreign objects
Remove foreign objects from between steering
column shroud and steering wheel/steering
column rotating components
Click
Clockspring or steering column
multifunction switch LH
Correctly install and install new components as
required
Loose universal joint pinch bolt
Install a new universal joint pinch bolt and
tighten to correct specification.
REFER to: Specifications (211-00 Steering System - General Information, Specifications).
Squeak
Steering column shroud joints
Apply Krytox spray to steering column shroud
joints
Clockspring
Install new clockspring as required

2. Free play should be between 0 and 6 mm (0 and 0.24 in) at the steering wheel rim. If the free play exceeds this limit,
either the ball joints are worn, the lower steering column joints are worn or the backlash of the steering gear is
excessive.

CAUTION: DO NOT attempt to adjust the steering gear yoke. Failure to follow this instruction will invalidate the steering
gear warranty.
3. The backlash of the steering gear cannot be adjusted, install a new steering gear if excessive backlash is diagnosed.

4. Grasp the steering wheel firmly and move it up and down and to the left and right without turning the wheel to check
for column bearing wear, steering wheel or steering column.
Power Steering Fluid Condition Check

1. Run the engine for 2 minutes.
2. Check the power steering fluid system level.

3. Observe the color and the odor. The color under normal circumstances should be dark reddish, not brown or black.

4. Using a suitable clean syringe extract a suitable amount of fluid from the reservoir.
5. Allow the fluid to drip onto a facial tissue and examine the stain.

6. If evidence of solid material is found, the power steering fluid system should be drained for further inspection.

7. If fluid contamination or steering component failure is confirmed by the sediment in the power steering fluid system,
refer to Steering Fault Diagnosis by Symptom Charts in this section.
Power Steering Pressure Test

Test Equipment



Item Part Number Description 1 211-011 Pressure Gauge Hose 2 211-011-08 Pump Return Hose 3 211-011-07 Pump Return Hose Connector 4 211-011-03/2 Test Equipment to High Pressure Hose Adaptor 5 211-011-03/1 Pump High Pressure Outlet to Hose Adaptor 6 211-011-02 Pump Adaptor to Control Valve Hose 7 211-011-01 Control Valve 8 211-011 Pressure Gauge 9 - 'O' Ring Seal The measurement of the maximum system pressure, (which is governed by the pressure relief valve) is achieved by inserting
the Service Tool (pressure gauge and adaptors) into the fluid circuit of the power steering system. Run the engine at idle
speed, turn the steering from lock to lock and read the maximum pressure recorded on the gauge.

Installing Test Equipment

To install the pressure test equipment:

Place a suitable drain tray below the power steering pump.
Install a hose clamp on the reservoir to pump hose prior to disconnecting any hoses, to avoid unnecessary loss of fluid.
Disconnect the hose from the power steering pump high pressure outlet.
Install the pump outlet to hose adaptor (5). Do not omit the 'O' ring seal (9).
Connect the power steering pump adaptor to control valve hose (6) of the test equipment.
Install the adaptor (4) in the high pressure hose previously removed from the power steering pump outlet.
Connect the connector (3) of the test equipment hose (2) to the adaptor (4).
Remove the hose clamp from the reservoir hose.
Start the engine to check the system pressure. www.JagDocs.com