1998 JAGUAR X308 speed

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

clos
ed outlet valves.
Traction Control
Trac

tion control has the same capabilities as ASC but with th
e added ability to actuate the brakes of the spinning wheel.
This enhances ASC by improving acceleration particularly on surfaces with uneven friction , e.g. one wheel on ice the other
on tarmac.
When wheelspin occurs, brake line pressure to the slipping wheel is generated, to operate that wheel's brake. The BCM
achieves this by closing the cut-off solenoid valve and oper ating the hydraulic pump. Brake fluid is then drawn from the
reservoir through the non-actuated mast er cylinder to the brake caliper.
A 'TRAC' amber warning light flashes on the instrument panel when the system detects a spinning wheel.
The traction control system uses a brake control modulator with nine solenoid valv es: four normally open inlet valves and
four normally closed outlet valves and one special isolating va lve. The outlet valves control the brakes of each each rear
wheel individually on the traction control system.
Rear Wheel Speed Senso
rs and ABS/TCCM Circuit Diagram

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

Make sure the ignition is off. 1
Disc
onnect the ABS module connector, LF27.
2
M
e
asure the resistance between LF27, pin 17 (W) and FL01, pin 02 (W).
3
I
s
the resistance less than 5 ohms?
Yes GO to C3
.
No
Re
pair the high resistance circui
t. This circuit includes intermed iate connector, LF02. Refer to the
electrical guides. Clear the DTC, check for normal operation.
C3: CH
ECK THE WSS RETURN CIRCUIT CONTINUITY
Measure

the resistance between LF27, pin 18 (R) and FL01, pin 01 (R).
1
Is

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, LF01. Refer to the
electrical guides. Clear the DTC, check for normal operation.
PI
NPOINT TEST D : CHECK THE RIGH
T-HAND REAR WSS AND CIRCUITS
•
NOTE: Check connectors and pins for damage/corrosion
(see visual inspection).
• NO
TE: Check the WSS ring condition, whee
l bearing etc. Before beginning pinpoint test s refer to the visual inspection.
TES
T
CONDITIONS
D E
TAILS/RESULTS/ACTIONS
D1: CHECK

THE WSS OUTPUT
Disc
onne
ct the ABS sensor connector, RA02.
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 D2
.
No
If
the WSS ring is in good condition, install a new WSS.
REFER to: Rear Wheel Speed Sensor
(206-0
9 Anti-Lock Control, Removal and Installation).
D
2
: CHECK THE WSS SIGNAL CIRCUIT CONTINUITY
Make sure the ignition is off. 1
Disc

onnect the ABS module connector, LF27.
2
Measure t

he resistance between LF27
, pin 07 (O) and RA02, pin 01 (O).
3
Is
the resistance less than 5 ohms?
Yes GO to D3
.
No Re
pair the high resistance circui
t. This circuit includes intermed iate connector, LA02. Refer to the
electrical guides. Clear the DTC, check for normal operation.
D3:
CHECK THE WSS RETURN CIRCUIT CONTINUITY
Meas
ure t
he resistance between LF27
, pin 06 (Y) and RA02, pin 02 (Y).
1
Is
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, CA09. Refer to the
electrical guides. Clear the DTC, check for normal operation.
PI
NPOINT TEST E : CHECK THE LEFT-HAND REAR WSS AND CIRCUITS
•

NOTE: Check connectors and pins for damage/corrosion
(see visual inspection).
• NO
TE: Check the WSS ring condition, whee
l bearing etc. Before beginning pinpoint test s refer to the visual inspection.
TES
T
CONDITIONS
D E
TAILS/RESULTS/ACTIONS
E1
: CHECK THE W
SS OUTPUT
Disc
onne
ct the ABS sensor connector, LA02.
1
Connec
t
a multimeter set
to read alternating curr ent volts (AC volts) between pins 1 and 2 of the
sensor.
2