1998 JAGUAR X308 Speed Sensor

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

Anti-Lock Control -
Lubri
cants, Fluids, Sealants and Adhesives
Torques
Brake Tube, Hoses and Bracket Torques
CAUTI
ON: Replacement of
nuts and bolts: Various thread-locking devices are used on nuts and bolts throughout the
vehicle. These devices restrict the number of times a nut or bolt can be used. See section 100-00 for information.


UnitS
pecification
Brake flu

id
ITT Supe
r Dot 4
Com

ponent
Nm
Bol

t - front wheel speed sensor
8-
10
Bolt

- rear wheel speed sensor
8-
10
Bo

lt - hydraulic control unit to bracket
8-
10
Bolt -

hydraulic control unit bracket to body
10
-14
Hub rotor nut2

70-330
Com

ponent
Nm
Bleed n

ipple - front
4-
6
Bleed n

ipple - rear
8-1
1
Hose to fr

ont caliper
10
-14
Hose banjo to rear caliper -

bolt
30
-40
M1

0 hose locknut
15
-20
M10

brake tube female-nut
13
-17
M10

brake tube male-nut
13
-17
M12

brake tube male-nut
15
-20
M18

brake tube male-nut
22
-28
Brake tube clip retention

-bracket to body
4-
6

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

It e
m
Par
t
Number
De
scr
iption
1—ABS /
T
CCM
2—E
n
gine compartment fuse-box
3—TCM (supercha
r
ged)
4—ECM

5—TCM (n ormally
aspirated)
6—Left rear
w
heel speed sensor
7—Ri
ght
rear wheel speed sensor

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.

Pinpoint tests

W
S
S circuit: short
circuit to power
WSS f
ailure
C1
175Left -hand re
ar wheel speed
sensor (WSS) circuit failure
W S
S circuit: open
circuit
WS
S circuit: short
circuit to ground
W S
S circuit: short
circuit to power
WSS f
ailure
F
or l
eft-hand rear WSS test
s. GO to Pinpoint Test E.
C1267Modulat or valv
e failure
Supply volt
ages
to valve
solenoids or sensors out of range
Fo
r power and ground tests. GO to Pinpoint Test
A.
B1342CAN co
mmunication circuit
failure
CAN :
open circuit fault

CAN:
short circuit to
ground
CAN :
short circuit to
power
Fo
r CAN tests. GO to Pinpoint Test
F.
B1676Supply volt
age out of range
Supply voltage:
too
low
Supply volt age:
too
high
Check fo
r DTCs indicating a charging system fault.
Rectify as necesssary.
PI
NPOINT TEST A : MODULE
POWER AND GROUND SUPPLIES
TES
T
CONDITIONS
D E
TAILS/RESULTS/ACTIONS
A
1
: CHECK THE POWER SUPPLY FUSES
Make sure the igniti
on is turned off. 1
Chec
k fuses 04, 16 and 18 of the engine compartment junction box.
2
Are th
e fus
es in good condition?
Yes GO to A2
.
No
Install a new f
use as
necessary. Check the syst em for normal operation. If the fuse fails again,
check the circuit for a short circuit to ground. Refer to the electrical guides.
A2: CHECK THE PERMANENT
POWER SUPPLY (1) TO THE MODULE
Disc

onnect the ABS module connector, LF27.
1
Measure the voltage between LF
2
7, pin 09 (NR) and ground.
2
Is the vol
t
age greater than 10 volts?
Yes GO to A3
.
No Re
pair the circuit between the engine compartment
junction box, fuse 16, and LF27 pin 09. Refer to
the electrical guides. Clear the DTC, check for normal operation.
A3: CHECK THE PERMANENT
POWER SUPPLY (2) TO THE MODULE
Meas
ure t
he voltage between LF27, pin 25 (NW) and ground.
1
Is the vol
t
age greater than 10 volts?
Yes GO to A4
.
No
Re
pair the circuit between the engine compartment ju
nction box, fuse 18, and LF27 pin 25. Refer to
the electrical guides. Clear the DTC, check for normal operation.
A4: CHECK
THE IGNITION POWER SUPPLY TO THE MODULE
Make sure the ignition is on. 1
Measure the
voltage between LF 2
7, pin 20 (WU) and ground.
2
Is the vol
t
age greater than 10 volts?
Yes GO to A5
.
No Re
pair the circuit between the engine compartment ju
nction box, fuse 04, and LF27 pin 20. Refer to
the electrical guides. Clear the DTC, check for normal operation.
A5: CHECK
THE GROUND SUPPLY TO THE MODULE

Make sure the ignition is turned off. 1
Meas
ure the resistances between LF27,
pins 08 and 24 (B) and ground.
2
Are
the resistances less than 5 ohms?
Yes The power and ground supplies to the module are ok . Recheck the DTCs for codes indicating a fault
elsewhere.
No Repair the high resistance circui t. Refer to the electrical guides. Clear the DTC, check for normal
operation.
PINPOINT TE
ST B : CHECK THE RIGHT-HAND FRONT WSS AND CIRCUITS
•
NOTE: Check connectors and pins for damage/corrosion
(see visual inspection).
•
NOTE: Check the WSS ring condition, whee
l bearing etc. Before beginning pinpoint test s refer to the visual inspection.
TE
ST
CONDITIONS
D
ETAILS/RESULTS/ACTIONS
B1: CHECK

THE WSS OUTPUT
Disc

onnect the ABS sensor connector, FR01.
1
Connec

t a multimeter set
to read alternating curr ent volts (AC volts) between pins 1 and 2 of the
sensor.
2
Spin
the wheel by hand and check the meter display.
3
Doe

s the sensor generate a voltage?
Yes GO to B2
.
No

If the WSS ring is in good condition, install a new WSS.
REFER to: Front Wheel Speed Sensor
(20
6-09 Anti-Lock Control, Removal and Installation).
B2:

CHECK THE WSS SIGNAL CIRCUIT CONTINUITY
Make sure the ignition is off. 1
Di

sconnect the ABS module connector, LF27.
2
Meas

ure the resistance between LF27
, pin 03 (Y) and FR01, pin 02 (Y).
3
I
s the resistance less than 5 ohms?
Yes GO to B3
.
No

Repair the high resistance circui t. This circuit includes intermediate connector, LF02. Refer to the
electrical guides. Clear the DTC, check for normal operation.
B3:
CHECK THE WSS RETURN CIRCUIT CONTINUITY
Meas

ure the resistance between LF27
, pin 04 (G) and FR01, pin 01 (G).
1
I
s the resistance less than 5 ohms?
Yes The WSS and circuits are OK. Check for DTCs indicating a possible module failure.
No Repair the high resistance circui t. This circuit includes intermediate connector, LF02. Refer to the
electrical guides. Clear the DTC, check for normal operation.
P
INPOINT TEST C : CHECK THE LEFT-HAND FRONT WSS AND CIRCUITS
•
NOTE: Check connectors and pins for damage/corrosion
(see visual inspection).
•
NOTE: Check the WSS ring condition, whee
l bearing etc. Before beginning pinpoint test s refer to the visual inspection.
TE
ST
CONDITIONS
D
ETAILS/RESULTS/ACTIONS
C1

: CHECK THE WSS OUTPUT
Disc

onnect the ABS sensor connector, FL01.
1
Connec

t a multimeter set
to read alternating curr ent volts (AC volts) between pins 1 and 2 of the
sensor.
2
Spin
the wheel by hand and check the meter display.
3
Doe

s the sensor generate a voltage?
Yes GO to C2
.
No

If the WSS ring is in good condition, install a new WSS.
REFER to: Front Wheel Speed Sensor
(20
6-09 Anti-Lock Control, Removal and Installation).
C2

: CHECK THE WSS SIGNAL CIRCUIT CONTINUITY