1998 JAGUAR X308 Amp

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

The brake
control modulator comprises:
a A

BS/TCCM
a h

ydraulic control unit,
an electrically driven hydrau

lic pump,
two low pressure accumulato

rs and damping chambers.
ABS/TCCM


The AB
S/TCCM is integrated with the hydrau
lic control unit. It houses the solenoids that operate the hydraulic control unit's
input and return valves; the valve stems locate into the ABS/TCCM's solenoids. There is no electrical connection between
the ABS/TCCM and the hydraulic control unit.
The ABS/TCCM constantly monitors the brake electronic system by passing self-checking electrical pulses around the circuit.
The self check procedures carried-out by the ABS/TCCM are listed below:
1. 1. Monitoring of the operating voltage: the control mo dule will shut-down should the voltages not be
(approximately) in the range of 9 to 19V.
2. 2. The pump is monitored for volt age supply and voltage feedback.
3. 3. Monitoring for disturbance, where a failure may be caus ed by external radio frequency interference, internal
leakage current, defective valve transistor or a faulty valve.
4. 4. Internal controller failure, de tected by a RAM and ROM test.
5. 5. The controller area network (CAN) micr o-controller checks for correct operation of the communication network
and performs a RAM self-check.
CAUTION: Disconnection of ABS/TCCM connectors may introduce other fault codes. Following rectification and
reconnection, ensure that no induced codes exist.
5.
Signals processed by the ABS/TCCM are also sent to the CAN for vehicle use, such as the instrument cluster speed display,
cruise control and stability/traction control.
Hydraulic Control Unit

Control of
the fluid pressure to
the front and rear brakes is by means of the valves contained in the hydraulic control unit.
The valves are operated by solenoids housed in the ABS/TCCM.
Hydraulic Pump
The
hydraulic pump is integrated
with the hydraulic control unit.


Bra
ke Control Modulator

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

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 th e fluid circuit of the power steering system. Run the engine
at idle speed, turn the st eering from lock to lock and read the ma ximum pressure recorded on the gauge.
Installin
g Test Equipment
To
in
stall the pressure test equipment:
Pla
c
e a suitable drain tray be
low the power steering pump.
Install a hose clamp on
the re
servoir to pump hose prior to disconnecting any hoses, to avoid unnecessary loss of
fluid.
Disc
onnect the hose from the power st
eering pump high pressure outlet.
Install the pu
mp 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 th e adaptor (4) in th
e high
pressure hose previously removed from the power steering pump outlet.
Conn
ect the connector (3) of the test equipment hose (2) to the adaptor (4).
R
e
move the hose clamp fro
m the reservoir hose.
Start th
e engine.
With the control valve (7) OPEN and the engine idli ng, the following system pressures may be checked:
Du
ring turning.
W
h
en the steering is
held on full lock.
With
the steeri
ng at rest.
• CAUTIONS:
To avoid excessive heating of the po wer steering pump, do not close the valve for longer than 5 seconds maximum.
Do not drive the vehicle with the test equipment installed.
With the control valve (7) CLOSED the power steering pump maximum ou tput pressure can be checked.
Removing Test Equipment
To
remove the test equipment:
Install a hose clamp
on
the reservoir to power steering pump hose.
Re
movi
ng the test equipmen
t is a reversal of the in stallation instructions.
Install a new '
O
' ring seal (9) to the power steering pump high pressu
re outlet to hose connection.
Instal
l the original hose to
the power steering pump.
Re
move the clamp from the reservoir to
the power steering pump hose.
Top-up the reservoir flui
d.
Ble
e
d the power steerin
g system. For additional information,
REFER to Power Steering System Bleeding
- in thi
s section.
Stee
ring Fault Diagnosis by Sympt
om Charts
Leakage
52
11-0
11-03/1
Pump High Pressure Ou
tlet
to Hose Adaptor
621
1
-011-02
Pump Adaptor
to Contro
l Valve Hose
721
1
-011-01
Control Valve
82
11-
011
Pressure Gauge
9-'O
'
Ring Seal
Cond
iti
on
Possib
l
e Sources
Acti
o
n
Co
nfirm
the position of the fluid
leak.
CLEAN th
e area of the leak.
In
s
pect the area and confirm the exact position of leak.
Make sure the fluid
is not from anoth
er system on
the vehicle.

Hiss (Swish)
Hiss or Val
ve Hiss is a high-frequency so
und coming from the steering gear when the system is loaded. It is a rushing or
"swish" noise that doesn't change frequency with RPM. Hiss is the general noise generated by the flow of hydraulic fluid
through restrictions in the steer ing system. Restrictions include the rotary stee ring valve, power steering tubes, connectors,
tuning orifices, etc. Hiss can be air- borne and structure-borne, but the structure-borne path through the steering
intermediate shaft is usually dominant.
Moan (Groan)
Moan is the general structu r
e-borne noise of the steering system. Moan is primarily transmitted to the driver via the body
structure through the pump mount, engine mounts, power steering lines and power steering brackets. On some vehicles,
moan is a load humming noise, often present when the wheel is turned and the system is loaded. It may change frequency
with engine RPM and if the sy stem is loaded or unloaded.
Rack Knock (R
ack Slap)
CAU
T
ION: DO NOT attempt to adjust the stee
ring gear yoke. Failure to follow this instruction will result in the steering
gear warranty to become invalid.
Rack Knock is a rattle sound an d steering wheel vibration caused by separation of the steering gear and pinion while driving
over bumps. It is a structure-borne noise transmitted throug h the intermediate shaft and column. Rack knock can also be
heard as a "thump" or impact noise that occurs with the vehicle stationary when the steering wheel is released from a
loaded position and allowed to return to rest . Noise occurs with the engine on or off.
Rattles
Ra
ttles are noises caused by knocking or hitting with components in the steering system. Steering rattles can occur in the
engine compartment, the suspension, or the passenger compartment . Rattles can be caused by loose parts, movable and
flexible parts, and improper clearances.
Squea k
s/Scrapes
Squeaks/Scrapes are noises due
to fri
ction or component rubbi
ng anywhere in the steering system. Squeaks/Scrapes have
appeared in steering linkages and jo ints, in column components and in co lumn and steering wheel trim parts.
Weep
We
ep is an air-borne noise, occasionally
generated when turning the steering across lock at a constant rate. When present
on a vehicle the noise, once initiated can often be maintained across a large proportion of the available steering movement.
Whistle
Wh
istle is similar to hiss but is louder and of a higher frequency. It is also more
of a pure tone noise than hiss. Whistle is
air-borne and is generated by a high flow rate of hydraulic fluid through a small restriction.
Zip

Zip n
o
ise is the air-borne noise
generated by power steerin g pump cavitation when power steering fluid does not flow freely
through the suction hose from the rese rvoir to the pump. Zip primarily occurs during cold weather at start-up.
Steering System Vibrations and Harshne
ss
Buzz
Buzz is a tactile rotary vi

bration felt in
the steering wheel for slow steering inputs. Buzz can also be called a grinding feel
and it is closely related to grunt and is caused by high system gain with low damping. Buzz is generally excited during
parking manoeuvres with low to medium speed steering input.

Buzz (E
lectrical)
A
different steering buzz can be caused by
pulse width modulated (PWM) electric actuators used in variable assist steering
systems. This buzz is felt by turning the ignition key to run without starting the engine and holding onto the steering wheel.
In extreme cases, the buzz can be felt with the engine running also.
Column/Steering Wheel
Shake
Column shake is a low f
requenc
y vertical vibration excited by primary engine vibrations.
Nibble (Shimm
y)
Steeri
ng nibble is a rotary oscillation or
vibration of the steering wheel, which can be excited at a specific vehicle speed.
Nibble is driven by wheel and tire imbalance exciting a suspensi on recession mode, which then translates into steering gear
travel and finally steering wheel nibble.
Shudder (Judd
er)
Shudder i
s a low frequency oscillation of th
e entire steering system (tire, wheels, st eering gear and linkage, etc.) when the
vehicle is steered during static-park or at low sp eeds. Shudder is very dependent on road surface.
Torque Ri
pple
Torque rippl
e is a concern with Electric Power Steering (EPS) sy
stems. Torque ripple is most evident at static-park steering
the wheel very slowly from lock to lock. Torque ripple is primarily caused by motor commutation.
Torque/Veloc
ity Variation
(Phasing/Effort Cycling)
Steeri
ng wheel torque variation oc
curring twice in one revolution is normally as a result of problems with the lower steering
column (intermediate shaft), but foul cond itions generally result in either constant stiffnes s or single point stiffness.
Depending upon the orientation of the joints, the steering can fe el asymmetric (torque falling off in one direction and rising
in the other) or else it can simply have pronounced peaks and troughs as the steering moves from lock to lock.
Wheel Fight
(Kick Back)
W
heel fight is excess feedback of sudden road forces through th
e steering system and back to the driver. It is evaluated at
all vehicle speeds over cobblestones, rough roads, and potholes . The tires, wheels, and suspension generate forces into the
steering systems. Steering friction, hydraulic damping, hydr aulic compliance, mechanical compliance, steering ratio, and
assist gain all affect how much is transmitted to the driver.
Stee
ring Linkage
CAUTI
ON: 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.
• NOTE: The following steps must be carried out with assistance.
1. 1. With the wheels in the straight ahead po sition, gently turn the steering wheel to the left and the right to check for
free play.
2. 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.