1998 JAGUAR X308 lamp

Hydraulic Br
ake Actuation -
Hydraulic Brake Actuation
Description and Operation

The hydraulic brake system is split in to two independent circuits: the primary ci rcuit operates the front brakes and the
secondary circuit operates the re ar brakes. This type of system prevents comple te brake failure in the event of a brake tube
fracture.
The hydraulic brake system consists of the following components:

Ite
m
Descr
iption
1Pedal Housi

ng / Booster - refer to 206-07
2Vacu

um Hose - refer to 206-07
3Mast
er Cyl
inder / Reservoir
4Primary Brake Circu
i
t
5Secon
dary Brake Circuit
6Hydrauli c
Pump / Motor Unit - refer to 206-09
7ABS/Traction

Control Control Modu
le (ABS/TCCM) - refer to 206-09
8Hydraulic Cont
rol Unit (HCU) - refer to 206-09
6/
7/
8
Br
ak
e Control Modulator
9Brake
Di
sc - refer to 206-03 or 206-04
10Brake
Cali
per - refer to 206-03 or 206-04
11W
h
eel Speed Sensor - refer to 206-09
12ABS Warning Lamp -
refer to 206
-09
13Brake F
l
uid Level Warning-Lamp

The t
andem master cylinder contains two in
dependent pistons, fluid pressure to each brake circuit is controlled by its own
individual piston. Brake fluid is supplied to the master cylinder by the reservoir, which is divided into two sections to preve nt
total fluid loss should one of the circuits fail. A port situated at the bottom of each section of the reservoir supplies the f luid
to each piston.
The fluid reservoir has a fluid-le vel indicator switch installed, which operates when the fluid level is low, causing the brake
fluid level warning-lamp to illuminate.
Bra
ke Caliper
The brake
calipers are of the single piston
type. The caliper carrier, which is secured to the vertical link by two bolts, carr ies
the single-piston caliper housing. The cali per housing is secured to the caliper carrier by two guide-pins and an anti-rattle
spring. When the brakes are applied, the caliper-housing piston pushes the brake pad in front of it, to wards the brake disc.
This movement forces the calipe r housing to move along the guid e-pins, in the opposite direction of the piston, to apply the
second brake pad.
Br
embo Brake Caliper
The four
cylinder brake caliper is rigidly attached to the vert
ical link via an anchor bracket. The caliper is a split assembly
with each side of the caliper, housing two pistons. The two-pairs of opposed pistons act direct ly on the brake pads mounted
one each side of the disc.




Mast
er Cylinder and Reservoir

8. Posi
tion absorbent cloth underneath master cylinder to collect
brake fluid spillage.

9. Di
sconnect brake tubes from master cylinder.
Install plugs to brake tu

bes an
d master cylinder ports.

10
.
From driver footwell, disconne ct throttle inner cable from
pedal.
Re
move grommet.
Relea

se cable from pedal.

11
.
Disconnect stop-lamp-switch connector.
Move carpet.
Disc
onnect electrical connector.
12. From engine compartment, remo ve throttle cable from pedal
housing.
Re
lease grommet.

8. Conne ct
low-level warning connector to master cylinder.

9. Inst al
l cruise control vacuum-valves, mounting bracket.
Install and tigh
ten bolts.

10 . Conne
ct stop lamp switch connector.
Conne
ct
connector.
Re
posi
tion carpet.
11. Connect battery ground cable (IMPORTANT, see operation
86.15.15 for further information).
12. Bleed brake system. See operation 70.25.03.
13. Install engine compartment rear cover. Refer to operation
76.11.35.
14. Remove paint-work protection covers and close engine
compartment.

15 . Conne
ct battery ground cable (I
MPORTANT, refer to operation
86.15.19 for further information).

Anti-Lock Control - Anti-Lock Control
Description and Operation


Wheel Spe
ed Sensors
Each
wheel is monitored by a wheel speed se n
sor, to detect the speed of movement of
a toothed gear that is driven by the
wheel. Signal's generate d by the toothed gear passing th e sensor are sent to the ABS/TCCM to communicate the speed of
wheel rotation and any rapid change of wheel speed.
The frequency of the sinusoidal output voltag e signal from the sensor, is proportional to road wheel rotational speed and the
number of teeth on the toothed gear. The amplitude of the volt age is dependent upon the 'air gap' between the sensor and
toothed wheel, therefore it is important that this preset gap remains clear and undisturbed.
Ite
m
De
scr
iption
1Pe
dal Housi
ng / Booster - refer to 206-07
2Vac
u
um Hose - refer to 206-07
3Mas
t
er Cylinder / Reservoir - refer to 206-06
4Pri
m
ary Brake Circuit - refer to 206-06
5Sec

ondary Brake Circuit - refer to 206-06
6Hydraulic

Pump / Motor Unit
7ABS/Traction

Control Control Module (ABS/TCCM)
8Hydraulic Cont

rol Unit (HCU)
6/
7/
8
Br
ak
e Control Modulator
9Brake
Di
sc - refer to 206-03 or 206-04
10Brake
Cali
per - refer to 206-03/206-04
11Wh
ee
l Speed Sensor
12ABS Warning Lamp
13Brake
Fl
uid Level Warning-Lamp - refer to 206-06

It is a reciprocating two
-circuit pu
mp in which one brake circuit is as signed to each pump circuit.
It supplies th
e fluid pressure and vo
lume to supply the brake circuits under ABS and Traction control.
The pump is driven by an electri
c motor, with the pump
housing incorporating two lo w pressure accumulators and
damping chambers for each brake circuit.
The ac cu
mulator stores the pressure and smooths out the output pu
lses from the pump.
ABS Warning Lamp
The sys
tem will be set in a fail-safe mode if a problem is de
tected; a warning lamp on the instrument panel will notify the
driver there is a problem.
Anti-Lock Braking Sy
stem (ABS)
The AB
S components are combined with
an hydraulic booster and a tandem master cylinder to provide a two circuit braking
system. The system comprises, four wheel speed sensor s, a brake control modulator and an ABS warning lamp.
Should a wheel start to lock-up during braking a signal tr ansmitted from the wheel speed sensor to the brake control
modulator will start the hydraulic pump. The brake control modula tor will close the input valve of the line connected to the
locked-wheel to stop any increase in fluid pressure to the br ake caliper. If this fails to prevent the wheel locking, the
pressure in the caliper will be decreased by opening the return valve until th e wheel starts accelerating again. The fluid
pressure from the return va lve is directed into the low pressure accumulator, housed in the pump.
From the low pressure accumulator, fl uid is pumped through the damping cham ber to the brake master cylinder. The
pressure to the brake caliper will then be increased in small steps to maintain maximum adhesion between the tire and road
surface. This is achieved by closing the return valve, and opening the input valve and using the hydraulic pump to increase
the pressure.
Although the system senses all four wheels independently, the rear wheels are regulated as a pair. If a sensor on a rear
wheel detects a wheel decelerating rapidly, then the fluid pressure to both wheels is reduced. The fluid pressure is then
dictated by the wheel having the lowe st adhesion with the road surface.
The ABS system will be set in a fail-safe mode if a problem is detected; a warn ing lamp on the instrument panel will notify
the driver there is a problem. The brake system will still operate conventionally and with the same standard of performance
as a vehicle not equipped with ABS.
Automa tic Stability Control (ASC)

Th
e ASC utilizes the ABS sensing arrangement to provide the maximum traction force to propel the vehicle.
The ASC is switched on when the engine is started. The system can be switched off by pressing the 'ASC OFF' (the switched
is marked 'TRAC OFF' on vehicles fitted with traction control). The switch, which is situated in the center console switchpack,
lights up to warn that the system is sw itched off. An 'ASC' amber warning light flashes on the instrument panel when the
system detects a spinning wheel.
The ASC system uses engine intervention to reduce the torque delivered to the drive wheels to prevent them spinning.
Engine torque is re duced in three ways:
The
throttle is moved towards the closed position.
The ignition is retarded. F
u
el is cut-off at the cylinder injectors.
Wheel spin is detected by the wheel sp eed sensors and communicated to the AB S/TCCM. The ABS/TCCM uses information
from the controller area network (CAN) to calculate the torque that the engine should produce to stop the wheel spinning.
Torque reductions are then requested from the engine control module (ECM ) through the CAN. The throttle is then
positioned to provide the target torque, which has been calculated to prevent wheel spin. During the transient phase of
torque reduction the fuel is cut-off and th e ignition retarded Both the fuel cut-off an d ignition retard will be restored to
normal when the throttle is set to its new position.
The ASC uses a brake control modulator with six solenoid va lves: three normally open inlet valves and three normally

Anti-Lock Control - Anti-Lock Control
D
iagnosis and Testing
Ov

erview
Fo
r information on the operation of the system:
REFER to: Anti
-Lock Control
(206-09 Anti-Lock Control, Description and Operation).
I

nspection and verification
1.
1. Veri
fy the customer concern.
2. 2. Visually inspect for obvious mech anical or electrical faults.
visual insp
ection
3.
3. If
an obvious cause for an observed or
reported concern is found, correct th e cause (if possible) before proceeding
to the next step
4. 4. Use the approved diagnostic system or a scan tool to retrieve any diagnostic trouble codes (DTCs) before moving
onto the DTC index.
Make sure that
all DTCs are cleared following rectification.
DTC Index
MechanicalElectrical
ABS se
nsors
W

heel speed sensor ring for
any damage/contamination
Hydrauli
c control unit (with attached ABS module) condition and
fitment
F
uses
Harnes

ses and connectors
War

ning light operation
Wh

eel speed sensors
Dynam

ic stability control (DSC)
switch
Stoplamp switch

ABS module Con

troller area network (CAN)
circuits
DT
C
De
scription
Possib
le causes
Acti
ons
C1

095
Pump mo
tor circuit failure
Module power or
gr
ound supply fault
Module

failure
Check the modu
le power and
ground supplies. GO to
Pinpoint Test A.
R
efer to the warranty policy and
procedures manual if a module is suspect.
C1
137
Control modu
le internal
circuit failure
Module power or
gr
ound supply fault
Module

failure
Check the modu
le power and
ground supplies. GO to
Pinpoint Test A.
R
efer to the warranty policy and
procedures manual if a module is suspect.
C1
145
Right
-hand front wheel speed

sensor (WSS) circuit failure
W
SS circuit: open
circuit
W
SS circuit: short
circuit to ground
W
SS circuit: short
circuit to power
WSS
failure
F
or right-hand front WSS tests. GO to Pinpoint Test
B.
C1
155
Left-hand front wheel
speed
sensor (WSS) circuit failure
W
SS circuit: open
circuit
W
SS circuit: short
circuit to ground
W
SS circuit: short
circuit to power
WSS
failure
F
or left-hand front WSS tests. GO to Pinpoint Test
C.
C1
165
Ri
ght-hand rear wheel speed

sensor (WSS) circuit failure
W
SS circuit: open
circuit
W
SS circuit: short
circuit to ground
F
or right-hand rear WSS test
s. GO to Pinpoint Test D.

3.3. If an obvi
ous cause for an observed or
reported concern is found, correct th e cause (if possible) before proceeding
to the next step.
4. 4. Check the power steering fluid condit ion. For additional information, REFER to Power Steering Fluid Condition
Check in this section.
5. 5. If the concern is not visually evid ent, verify the symptom and REFER to Steering Fault Diagnosis by Symptom
Charts in this section.
Steering Re
lay Harness Connector

Stee
ring Linkage In
spection and Backlash (Freeplay) Check
CAUTIO

N: Steering gear boots must be
handled carefully to avoid damage. Use new clamps when installing steering
gear boots.
Inspect the boots for cuts, deterioration, tw isting or distortion. Check the steering gear boots to make sure they are tight.
Install new boots or clamps as necessary.
REC O
NNECT all electrical item
s disturbed during testing
Ite
m
De
scr
iption
1Ste
e
rin
g tran
sduc
er
ground
2Igni
ti
on feed
3Steeri
ng transducer feed
4Ground
5Speed s
ensor signal
6Seri
a
l interface