sensor JAGUAR XJ6 1994 2.G Service Manual

Driveshafts & Final Drive
9.10 REAR HUB BEARING, RENEW
SRO 64.15.14
9.11
SRO 64.15.15
REAR HUB OIL SEAL, RENEW
Removal
= Disconnect vehicle battery ground lead.
= Slacken appropriate axle shaft hub nut.
. Support the vehicle at the rear and remove rear road
m: To aid assembly, markthe position of the head of the
hub carrier fulcrum, relative to the wishbone slot.
. Disconnect handbrake cable inner and outer.
. Remove brake caliper in accordance with Section 12, but do not disconnect hydraulics.
. Slacken hub carrier fulcrum and remove ABS sensor from
hub carrier.
. Remove axle shaft hub nut (and discard), collar and hub
carrier fulcrum.
. Using service tools JD 1D/7 and JD ID (Fig. I), push shaft
through hub and pull the hub carrier assembly clear.
. Using Hub tool JD 132 - 1 (1 Fig. 2) and a suitable press,
align the hub assembly tothetool ensuring the hand brake
expander locates into the tool cut out.
. Locate button JD 132 - 2 and press the hub from the
carrier.
. Remove the outer bearing race and seal from either the hub or the carrier and place the ABS rotor to one side.
. Remove from the carrier; bearing spacer, adjustable
spacer, inner race and seal.
Renew Bearings /Sea/($
wheel.
. Using a suitable drift remove the inner and outer bearing
cups.
. Clean all components paying particular attention to the re- moval of all tracesof lockingcompoundfrom the hub AND
axle shaft splines.
. Using service tools JD 550 - 4 /2,4 / 1 and 18G 134, fit new
cups to the hub carrier ensuring that they are 'square'and
fully seated.
Fit the new outer bearing race to the hub.
&&Q:
. Assemble the hub and race to the carrier along with bear-
Do not fit seals or 'pack' bearing at this point.
ing spacer (noting orientation) and the largest available
adjustable spacer,
i.e. 3.47 mm.
. Fit the new inner bearing and ABS rotor to the hub. Fig.
1
Fig.
2
. Apply a compressive load to the hub / bearing assembly, using a press, vice or long bolt. Ensure that the force that
. Measure the hub end-float, using service tool JD 13B dial test indicator (DTI).
. Using the indicated endfloat dimension, select a suitable adjustable spacer to give the specified pre-load.
m:
. Remove the outer bearing from the hub.
. Lubricate the bearings as specified.
. Locate the outer bearing to the hub carrier assembly.
the axle shaft
fixing would normally provide is not exceeded.
See Service Data, (preliminary pages) for pre
-load specification and typical example.
Issue 1 August 1994 8 X300 VSM

@ Steering
The rotaryvalve within the pinion housing on the 'Servotronic'system is fitted with a 'Hydraulic Reaction Piston' (HRP). The HRP moves axially, relative to the rotor, on ball bearing travellers (acting as a face cam) and is connected to the
sleeve
by a four bearing helical screw. Pressure applied eitherside of the HRP is translated into a rotational force which
resists torsion bar /valve displacement thus increasing steering effort. The amount of pressure applied to the HRP is
controlled by: a) the differential pressure on the rack piston, proportional tovehicle corneringforce and
b) the position
of the transducer valve controlled bythe SCM from information gathered on road speed. Road speed data is processed
from the left hand rear wheel speed sensor.
1 Electronic speedometei
2 SCM 3 Transducer 4 Reaction area 5 Reaction area
6 Checkvalve 7 Checkvalve
8 Choke 9 Choke
10 Reaction limitina valve 157-279 11 Reaction piston-
N Radial groove (return)
0 Radial groove (feed)
Fig.1 Sensors, valves & hydraulic flow - HIGH speed anti-clockwise rotation
X300 VSM Issue 1 August 1994 4

SECTION CONTENTS
Subsection Tit/e SRO Page
i to iv ............ Preliminary Pages .................................................................... i
12.1 ............. Anti-Lock Braking System (ABS) General Description ................................... 12.1
12.1.2.
........... Anti-lock Braking/ Traction Contd Operation ........................................ 12.3
12.1.3
............ Anti-lock Braking Operation ........................................................ 12.4
12.1.4
............ Actuation Components ............................................................. 12.5
12.1.5
............ ABSComponents ................................................................. 12.6
12.1.6
............ Calipers ........................................................................\
. 12.7
12.1.7
............ Parking Brake .................................................................... 12.9
12.1.8
............ Wheel Speed Sensors ............................................................. 12.11
12.1.9
............ Hydraulic Operation - ABS CM .................................................... 12.12
12.2
............. Fault Diagnosis and Testing ........................................................ 12.16
12.4
............. Brake System Bleeding ............................................................ 12.19
12.1.10
.......... Hydraulic Operation - ABS /TC CM ................................................. 12.14
12.3
............. Brake Fluid Level Check .......................................................... 12.18
12.4.1
............ System Bleeding - General Instructions .............................................. 12.19
12.4.2.
........... System Bleeding After Brake Fluid Renewal .......................................... 12.19
12.4.3
............ System Bleeding After Tandem Master Cylinder Renewal ............................... 12.19
12.4.4.
........... System Bleeding Afier Hydraulic Control Module Renewal ............................. 12.20
12.4.5.
........... Bleeding After Renewal of Caliper .................................................. 12.20
12.5
............. General Fitting Instructions ........................................................ 12.2 1
12.5.1 ............ General Fitting Instructions, Brake Fluid ............................................. 12.2 1
12.5.2. ........... General Fitting Instructions, Hoses .................................................. 12.2 1
12.5.3 ............ General Fitting Instructions, Pipes ................................................... 12.2 1
12.6 ............. Rear Wheel Speedsensor- Renew ............................... 70.60.04 ......... 12.22
12.7
............. Hydraulic Control Module- Renew ............................... 70.60.18/ 19 ..... 12.23
12.8
............. Pressure Conscious Reducing Valves .............................. 70.60.21 ......... 12.25
12.9
............. ABS/TCCM - Renew .......................................... 70.60.02/20 ..... 12.26
X300 VSM i Issue 1 August 1994

12.1 ANTI-LOCK BRAKING SYSTEM (ASS), GENERAL DESCRIPTION
The anti-lock braking system (ABS) components are combined with a hydraulic booster and tandem master cylinder (TMC) to provide a two-circuit braking system. The anti-lock braking system comprises the following components:
0 Four inductive wheel speed sensors, hub end mounted
0 ABS warning light
0 Hydraulic module.
The hydraulic module consists of an electric motor driven pump,
two low pressure accumulators, valve block and an
ABS electronic control module.
m: Electronic control modules for vehicles without traction control are designated ABS CM. Control modules for
vehicles with traction control are designated ABS /TC CM.
The valve block houses solenoid operated valves which are activated by voltage signals from the control module. The
signals are generated using wheel speed information received from the wheel speed sensors.
For vehicles without traction control the valves operate on three circuits, two front and one rear, as necessary to pre
- vent wheel locking during braking. Brake pressure is modulated individually at thefront wheels and collectively at the
rear. Rear wheel control operates on a 'select low' principle i.e. locking in either wheel is sensed, and controlled brake
pressure is applied to both wheels.
For vehicles with traction control the valves operate on four circuits. During ABS control the rear wheel are controlled
on a 'select low' principle (as above), but during traction control operation the rear wheels are controlled individually.
0
1yQfB: Functional and diagnostic information for the ABS CM and the ABS/TC CM is contained in the Electrical Diag-
nostic Manual (EDM), Section 12.
ABS Warning lamp / Traction Control Warning lamp /Fluid level Indicator
The ABS and traction control warning lamps, mounted in the instrument panel, indicate a fault in the ABS or traction
control. These systems are inhibited or disabled when the lamps are lit, although conventional braking is unaffected.
When the ignition is switched on, an ABS self test is initiated. During this test, the ABS and traction control warning
lamps are
lit for approximately 1.7 seconds and then extinguish. A fault is indicated if the warning lamps remain lit or
come on whilst the vehicle is being driven.
W: The ABS self test is masked by the 5 second lamp test initiated when the ignition is switched on.
The fluid level indicator lamp, mounted in the instrument panel, is
lit when the brake fluid falls below the minimum
mark on the brake fluid reservoir.
ABS / Traction Control - Inhibit / Disable
Faults conditions are detected by the ABS/TC CM which disables the ABS and traction control until the fault is rectified.
The ABS and traction control warning lights on the instrument pack remains lit whilst a fault exists. The system will
be disabled when the following conditions occur:
0
0 Valve failure
0 Sensor failure
0 Main driver failure (internal ABS /TC CM fault)
0 Redundancy error (internal ABS JTC CM fault)
0 Overvoltage J undervoltage
0 Pump motor failure.
0 Throttle valve actuator motor failure (traction control vehicles only).
0 Throttle valve actuator potentiometer failure (traction control warning light only).
X300 VSM 1 Issue 1 August 1994

The input frequency from each wheel speed sensor signal is translated by the ABS I TC CM, into a comparable wheel
speed. The ABS / TC CM continually monitors the system. False wheel speed information, such as sudden speed
changes in excess of 20 km / h or excessive speeds, are detected as a 'sensor malfunction'. The ABS / TC CM reacts
to fault conditions in the following ways:
Inhibit- ABS/traction control is inhibited until the sensed speed returns to within an acceptable limit, whereupon ABS
/traction control is restored. Conventional braking is unaffected. Depending on vehicle speed the ABS/traction control
warning lights may come on.
DisaMe - ABS /traction control is Disabled (switched off) and the ABS /traction control warning lights come on. The
system will not be restored until the engine is switched off and restarted orthe fault has been rectified. Afterthe system
has been disabled, the warning lamps remain on until the vehicle has reached a speed of 20 km/ h during thefirst igni- tion cycle after fault rectification.
Full diagnostic information for the ABS /TC
CM is given in the Electrical Diagnostic Manual (EDM), Section 12.
Issue 1 August 1994 2 X300 VSM

Brakes (a)
12.1.2. Anti-lock Braking / Traction Control Operation
The rear wheels are controlled collectively on a 'select-low' principle during ABS operation. During traction control,
separate circuits allow individual control of the rear wheels. To facilitate this the valve block has four outlet ports.
The
ABS/TC CM is integrated with the valve block. The pump, motor, valve block and control module are supplied as
a unit and are non-sewiceable. Faulty units must be renewed as a whole.
Both front and rear brakes on
all vehicles are fitted with single piston caliper assemblies. Ventilated brake rotors, with
provision for parking brake shoes at the rear, are fitted all round.
0
Issue 1 August 1994 X300 VSM 3
1. Vacuum booster 9. Pressure conscious reduction valve 2. Vacuum hose 10. Ventilated brake rotor 3. Tandem master cylinder 11. Single piston caliper 4. Primary brake circuit 12. %way brake pipe connector
5. Secondary brake circuit 13. Wheel speed sensor
6. Hydraulic pump / motor unit 14. ABS warning lamp 7. Valve block 15. Brake fluid level warning lamp
8. ABS/TCCM
Fig. 1 ABS / Traction Control System
The vacuum booster (see Fig.
1) is mounted on the brake pedal box and secured by three bolts. Brake pedal force is
increased by the vacuum booster which activates the Tandem Master Cylinder (TMC) intermediate piston. Brake fluid
is supplied to the pump inlet ports on two separate circuits. The primary circuit supplies the front brakes whilst the
secondary circuit supplies the rear brakes.

Pressure conscious reduction valves (PCRVs) are fitted between the outlet of the valve block and the rear brake circuit
to optimize. The valves are fitted to prevent over braking due to the increased size of the rear brake calipers which are
required for traction control. Up to a threshold of 15 bar, brake pressure to the front and rear brakes is equal. Above
15 bar the PCRVs reduce pressure to the rear brakes to provide a closer balance between front and rear brakes and
optimize road adhesion.
Wheel speed sensors are fitted to all wheels to transmit wheel speed information to the control module. The module
uses this information to modulate brake pressure during anti
-lock braking or traction control.
12.1.3. Anti-lock Braking Operation
170 287
1. Vacuum booster 9. Pressure conscious reduction valve
2. Vacuum hose 10. Ventilated brake rotor
3. Tandem master cylinder 11. Single piston caliper
4. Primary brake circuit 12.
%way brake pipe connector
5. Secondary brake circuit 13. Wheel speed sensor
6. Hydraulic pump I motor unit 14. ABS warning lamp 7. Valve block 15. Brake fluid level warning lamp
8. ABSICM
Fig. 1 Brake System (non-Traction Control)
The rear brakes (see Fig. 1) are controlled collectively on a
'select-low' principle. Under ABS braking conditions, equal
brake pressure is applied to both rear calipers, although only one wheel may have a tendency to lock.
The valve block has three outlet
ports, Brake fluid volume is supplied equally to the rear brakes via the %way brake
pipe connector.
Issue 1 August 1994 4 X300 VSM

12.1.5. ABS Components
Hydraulic Module
The hydraulic module is located under the bonnet adjacent
to the engine compartment firewall. It is secured within a steel mounting bracket at three securing points. All elec- tronic and power connections are made through one cable
loom connect ion.
The hydraulic pump
(1 Fig. 1) is a reciprocating two-circuit pump in which one brake circuit is assigned to each pump
circuit. The pump supplies adequate pressure and volume
supply to the brake circuits under anti
-lock braking condi- tions. The pump is driven by and electric motor (2 Fig. 1). The
pump housing incorporates two low pressure accumulators
and damping chambers for each brake circuit.
A modulator valve block
(3 Fig. 1) incorporates the ABS CM or ABS / TC CM (4 Fig. 1). Vehicles with traction control are
fitted with a throttle position actuator (5 Fig. I), which is an
electrical device controlled by the ABS 1 TC CM.
Valve blocks on vehicles without traction control comprise
six solenoid valves, three normally open (NO) inlet valves
and three normally closed
(NC) outlet valves. These valve
blocks have three outlet ports. Valve blocks on vehicles with
traction control comprise nine solenoid valves, four
NO inlet valves,four NC outlet valves and one special isolating valve.
Fig. 2 shows a hydraulic module for vehicles with traction
control. The valve block (2 Fig. 2) has four outlet ports (Indi- vidual control of the driven wheels).
A BS CM, A BS / TC CM
The ABS CM or ABS TCI CM locates beneath the modulator
valve block and is secured by
two screws. The CM houses
the solenoids which operate the inlet and outletvalves of the
modulator valve block. When fitted, the valve stems locate
in the
CM mounted solenoids. There is no electrical connec- tion between the CM and the modulator valve block. Fig. 3 shows an ABS TC 1 CM having nine solenoids.
The
CM functions include the following:
0 Providing control signals for the operation of ABS
and traction control solenoid valves
0 Calculating wheel speed from voltage signals trans- mitted by the wheel speed sensors
0 Monitoring of all electrical components
0 On Board Diagnostics (OBD): storage of possible fail- ures in a non-volatile memory.
The signals from the four wheel speed sensors are indepen
- dently processed by the ABS CM or ABSITC CM, calculating
numerical values which correspond directly to the wheel
speed. These values are converted into control signals for
pressure modulation during ABS control.
The ABS and traction control
are continuously monitored,
whilst the ignition is on,for possiblefaults and interruptions.
If a fault is detected, the module deactivates the ABS and
indicates this by lighting the ABS warning lamp. In a fault
condition, conventional braking is unaffected. The module
stores fault codes in a non
-volatile memory which can be
read via the OBD link.
U: For electrical diagnostic information on the ABS I traction control systems, refer to EDM, Section 12. Fia.
1
Fia. 2
Fin. 3 I
J70286
Issue 1 August 1994 X300 VSM

Brakes
12.1.8. Wheel Speed Sensors
A toothed wheel, which turns with the road wheel, induces an ac voltage signal in the wheel speed sensor. The fre-
quency and amplitude of the ac voltage varies directly in relation to wheel speed, providing the control module with
wheel speed information. Wheel speed sensors are fitted to each road wheel.
Front
The front sensors are mounted on the vertical link (1 Fig. 1).
Fig. 1
Rear
The rear wheel sensors are mounted on the hub carrier (Fig.
2).
Fin. 2
X300 VSM 11 Issue 1 August 1994

12.6 REAR WHEEL SPEED SENSOR - RENEW
SRO
70.60.04
. Drive the vehicle onto a ramp or raise the back and support
on two stands.
. Cut and remove the ratchet strap securing the speed sen- sor harness to the brake hose.
. Undo and remove the speed sensor to hub carrier secur- ing bolt (Fig. 1).
Remove the speed sensor from the hub carrier and allow
it to hang free, forward of the 'A' frame.
Open both rear doors and displace the rear seat cushion
from the seat pan brackets. Reposition the rear seat
cushion forwards.
9 Push the seat belts/ buckles through the seat cushion slots
and remove the rear seat cushion from the vehicle.
. Displace the RH side of the seat pan sound proofing (1 Fig. 2) to gain access to the speed sensor harness (2 Fig. 2).
9 Displace the speed sensor harness grommet (3 Fig. 2) from the seat pan aperture.
. Feed the speed sensor harness through the seat pan aper- ture and disconnect the multi-plug (4 Fig. 2).
9 Position the new speed sensor harness and connect the
multi-plug.
. Feed the speed sensor harness through the seat pan aper- ture to hang free below the vehicle.
. Refit and fully seat the speed sensor harness grommet to
the seat pan aperture.
Reposition theseat pan sound proofing to its original posi- tion.
Position the rear seat cushion and feed the seat belt / buckles through the slots.
Locate the rear seat cushion into the seat pan brackets (5 Fig. 2).
. Stow the seat belts / buckles.
. Position the speed sensor harness rearwards over the 'A'
Fit and tighten the speed sensor to hub carrier securing
Secure the speed sensor harness to the brake hose using
frame
and locate into the hub carrier.
bolt.
a ratchet strap. Trim the ratchet strap. Fig.
1
Fig. 2
Issue 1 August 1994 22 X300 VSM
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