electrical JAGUAR XJ6 1994 2.G Owner's Manual
[x] Cancel search | Manufacturer: JAGUAR, Model Year: 1994, Model line: XJ6, Model: JAGUAR XJ6 1994 2.GPages: 521, PDF Size: 17.35 MB
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Cooling System (V12
4.2.1 COOLING SYSTEM DESCRIPTION I
4.2.1.1 Major Components
o Engine crossflow radiator, incorporating a concentric tube cooler for the power steering fluid mounted in the
left
-hand radiator side tank. Vehicles with automatic transmission have a six-plate transmission fluid cooler
mounted in the right
-hand radiator side tank. A double-action temperature switch, for controlling the electric
radiator cooling fans, is mounted in the left
-hand radiator side tank.
0 Engine driven, viscous-coupled, radiator cooling fan
0 Two electrically operated radiator cooling fans, mounted in front of the radiator.
o Coolant circulating pump, belt driven from the engine crankshaft.
0 Coolant header tank with pressure relief cap and coolant level probe.
0 Two engine thermostats, one in each cylinder bank.
4.2.1.2
0 Heater matrix.
0 Electrically operated coolant circulating pump, mounted on the left-hand side of the engine bulkhead.
o Solenoid operated valve, located adjacent to the coolant circulating pump.
Components for Climate Control System
1
4.2.1.3 Operation
The configuration of the cooling system is shown in Sub-section 4.2.2.
The cooling system is pressurized, which allows the system to operate at a higher temperature without overheating.
The header tank is fitted with a pressure relief cap to protect the system against overpressure.
Under cold start conditions, coolant is forced by the engine driven water pump through each cylinder block and cylin
- der head to the thermostat housings. The thermostats are closed to give rapid engine warm up, hence the coolant is
returned via the engine cross pipe to the water pump inlet. When normal engine operating temperature is reached,
the thermostats open and coolant is diverted through the radiator before returning to the water pump inlet.
If the engine driven fan is unable to provide sufficient cooling, the electrically operated fans operate in series and paral
-
lel underthe control of the radiator mounted temperature switch. Under hot operating conditions, the electric fans may
continue to operate after the engine has been switched off. The fans stop automatically when the coolant temperature
has been reduced sufficiently.
The system also provides the coolant supply for the climate control system, which is described in Section 14.
I
I X300 VSM 1 Issue 1 August 1994
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WARNING: DO NOT REMOVE THE HEADER TANK PRESSURE CAP WHILE THE ENGINE IS HOT. IF THE CAP MUST
BE REMOVED, PROTECT THE HANDS AGAINST ESCAPING STEAM AND SLOWLY TURN THE CAP ANTI- CLOCKWISE UNTIL THE EXCESS PRESSURE CAN ESCAPE. LEAVE THE CAP IN THIS POSITION UNTIL
ALL THE STEAM AND PRESSURE HAS ESCAPED AND THEN REMOVE THE CAP COMPLETELY.
WARNING: WHEN DRAINING THE COOLANT WITH THE ENGINE HOT, PROTECT THE HANDS AGAINST CONTACT
WITH HOT COOLANT.
WARNING
: WHEN WORKING WITHIN THE ENGINE COMPARTMENT, KEEP CLEAR OF THE ENGINE DRIVEN RADI- ATOR COOLING FAN WHEN THE ENGINE IS RUNNING.
4.2.3.2 Working Practices
Whenfilling thesystem with coolant,ensurethatthevehicle isstanding on a level surfaceand thatthecoolant is poured
in slowly so that airlocks are not introduced into the system. Airlocks can seriously affect the operation of the climate
control system and can cause damage to the heater circuit pump.
Hose clips should always be positioned
so that there is proper access for tightening and that the clip does not foul or
interfere with the operation of any components.
4.2.3 SERVICE PROCEDURES
4.2.3.1 Safety Precautions
The anti-freeze specified in Appendix A1 must be used wherever possible. It is designed to afford the maximum cor- rosion protection to all metals found in the engine cooling system, as well as having the frost protection properties
necessary during the winter months. Should it not be available, then anti-freeze conforming to Ford Motor Company
specification
ESBM97B49-A may be used. To provide optimum temperature and corrosion protection, the specified
anti-freeze concentration must always be used. Once coolant has been drained from the system, it must be discarded
and not reused. Anti-freeze is harmful to the environment. Always dispose of used coolant safely and never pour it down a drain connected to the public sewer.
CAUTION: Never fill or topup the system with water only.
CAUTION
: Anti-freeze is harmful to paintwork. Coolant spillages must be wiped up immediately and the affected
area washed to remove all traces of coolant.
CAUTION: To prevent the possibility of damage to the heater circuit
pump, the pump should be electrically isolated if the ignition has to be turned ON while the cooling system is drained.
The drive belt must always be tensioned to the specified value and the tension checked at the correct point on the belt.
This information is given in Sub-section IV in the preliminary pages.
When tightening components, the torque figures given in Sub
-section II in the preliminary pages should always be
used for the fastenings listed.
When fitting a replacement thermostat, ensure that the jiggle-pin is to the top of the thermostat housing.
4.2.3.3 Coolant Change
The coolant must be changed at intervals of four years. The system should be drained from the radiator drain plug,
flushed and filled with fresh coolant. Flushing should be carried out thoroughly to remove all the old coolant from the
engine and heater matrix. (The heatervalve isopen with the ignition OFF). AfterfilIing,checkthecoolant concentration
with a hydrometer. For specified anti-freeze and coolant concentration, see in Appendix Al.
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4.2.5.2 Diagnostic Procedures
1
I Symptom ..
Overheating
herheating at
dle
roo cold ~~~
Possible Cause
Thermostat(s) stuck
closed
Incorrect thermostat rating
Faulty temperature gauge
Faulty temperature transmitter
Radiator core blocked
Radiator grille obstructed
Concentration of anti
-freeze
too high
Drive belt slack
Drive belt broken
Water pump seized
lnsuff icient coolant
Internally collapsed hoses
Incorrect ignition timing
Fuel
/ air mixture too weak
Incorrect valve timing
Cylinder head
gasket(s) leak-
ing
Brakes binding
Electric cooling
fan(s) not op- erating
Thermostat(s) stuck open
Incorrect thermostat rating
Thermostatb) not fitted
Electric cooling
fan(s) operat-
ing continuously
Faulty temperature gauge
Faulty temperature transmitter
Check
Cooling System (V12)
4.2.5 FAULT DIAGNOSIS
4.2.5.1 Introduction
The following diagnostic procedures are provided to assist properly qualified persons to identify and rectify the faults in the system which are most likely to be encountered. Reference is made to the Electrical Diagnostic Manual (EDM), which should be consulted for all electrical faults. When investigating faults relating to temperature, the prevailing
ambient temperature conditions should be taken into account. The climate control system is dealt with in Section 14.
Test thermostat(s)
Check thermostat operating
temperature
Refer to EDM
Refer to EDM
Check for
hotspots in radiator
Check grille for obstruction
Check strength of coolant
Check belt tension
Visual check Slacken drive belt and turn
water pump pulley by hand.
Check belt for damage
Check coolant level
Pressure test system and
check for deformation of hoses
Refer to EDM
Refer to EDM
Check valve timing
Pressure
-test system. (Check
for contamination of coolant in
header tank)
Check brake calipers for stick
- ing pistons and seized brake
pad pins
..
Refer to EDM
Test
thermostat(4
Check thermostat operating
temperature
Remove thermostat housing
and inspect
Refer to EDM
Refer to EDM
Refer to EDM
Remedy
Renew thermostat(s)
Renew thermostat(s1
Renew gauge
Renew transmitter
Flush or renew radiator
Remove obstruction from
grille
Drain and
fill with coolant of
correct concentration
Adjust belt to correct tension
or renew belt
if worn
Renew belt
Renew water pump. Renew
drive belt
if required
Top
-up coolant
Renew hoses as required
Rectify as required
Rectify as required
Correct valve timing
Renew head
gasket(s)
Rectify as required
Rectify as required
Renew
thermostat(s1
Renew thermostatb)
Fit thermostat(s)
Rectify as required
Renew gauge
Renew transmitter
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Automatic Transmission (AJ16)
Both types of automatic transmission comprise a hydrodynamic torque converter driving an epicyclic gear train which
provides four forward ratios and reverse. Gearshift selection is made by a hydraulic (or electronichydraulic) trans- mission control unit. Six gearshift positions are provided:
Position
'P' (Park) -the driven wheels are mechanically locked at the transmission.
Position
'R' (Reverse) - reverse gear selected.
Position
'N' (Neutral) - engine disconnected from drive-line and wheels.
Position 'D' (Drive)
- all four speed ranges are selected automatically with lock-up available in top gear only.
Position
'3' - automatic selection of the lowest three speed ranges only.
Position '2'
- automatic selection of the lowest two speed ranges only; the transmission is prevented from shift- ing up to the third and top speed ranges.
Immediate selection of a lower ratio is also available, within mapped limits, by 'kick
-down' (pressing the accelerator
pedal down beyond the normal full throttle position) for example when overtaking.
A brake pedal/gearshift interlock is incorporated in the shift lever mechanism. Theshift lever may only be movedfrom
the 'P' (Park) position if the ignition key switch is in position 'll', and the foot brake is applied. The ignition key cannot
be removed from the ignition switch unless the shift lever is in the 'P' (Park) position. Once the ignition key has been
removed, the shift lever is locked in the Park position. The gearshift interlock may be over-ridden manually in the event
of an electrical failure or when it is required to move the vehicle manually for access, ie for removal of the propeller
shaft.
8.1.1.1
Gearshift selection causes the appropriate gear to be selected through a cable operated shift lever on the side of the
Gear Selection (ZF 4HP 22)
transmission unit. When a gea; is selected, the shift points are determined by accelerator pedal position through a
throttle cable connection and by pressures equivalent to road speed derived from a centrifugal governor on the output
shaft.
Gearshift speed and quality are controlled by the hydraulic control unit located in the lower part of the transmission
housing. The control unit contains selector valve, control pistons and pressure valves.
The hydraulic control unit can be overridden by 'kickdown'. This is actuated by the final travel of the accelerator pedal
and causes the next lower gear to be selected.
8.1.1.2
Gearshift selection causes the appropriate gear to be selected through a cable operated shift lever on the side of the
transmission unit; the shift lever also operates a rotary switch attached to the side of the transmission unit. When a
gear is selected, the rotary switch provides an output or combination of outputs to the TCM, which continuously moni
- tors the gear selected in addition to output shaft speed and transmission oil temperature. Information from the Engine
Control Module (ECM) representing engine speed, load and throttle position is also fed to the TCM to enable the most
suitable gear to be selected.
Gear selection and gearshift speeds are controlled by the manually operated selector valve, a solenoid operated pres
- sure regulator and three solenoid valves. On receipt of signalsfrom the TCM, the three solenoid valves MVI, MV2 and
MV3, in various combinations with the safety valve, determine the appropriate gear range. The TCM, on receipt of
information of engine state and road speed, determines the shift speed.
The Performance Mode switch, located on the shift lever surround, provides two alternative shift speed patterns:
1. 'Normal (Economy) Mode' - designed for everyday use.
2. 'Sport Mode'
- gear shift takes place at higher road speeds to enhance performance.
The 'kick
-down' switch, located beneath the accelerator pedal, is actuated by the final travel of the pedal and signals
to the TCM that the next lower gear is to be selected.
Gear Selection (ZF 4 HP 24 E)
X300 VSM 3 Issue 1 August 1994
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10.1 STEERING SYSTEM DESCRIPTION
10.1.1 Steering Column Major Components
Integrated column assembly incorporating power, or manual, reach /tilt mechanism and lock.
Ignition switch.
Ignition interlock solenoid.
Key transponder coil.
Body attachment points.
Depending upon model, the steering column may be adjusted for
tilt and reach, either by electrical or manual means.
Power variants may be either automatically or manually adjusted and all types have the entry / exit feature.
10.1.2 Steering Column Operating Principle
Power Adjust: Two independent motor / gearbox assemblies provide infinite adjustment for reach and height within
approximate ranges of 35mm and
13O respectively. Adjustments may be automatically made in conjunction with the
seat memory facility or manually when the adjustment switch is used. It should be noted that selection of 'Off will
disable the automatic entry / exit mode.
Manual Adjust: The cable operated reach adjustment is infinite within a range of 35mm, with the desired position being
fixed
by a rack and wedge. Tilt variations are stepped at approximately 3O intervals with 6 positions being available,
the uppermost being unlatched.
From the uppermost position the column may be pulled down to engage the first detent without using the
tilt lever.
WARNING: MANUAL ADJUST ONLY: TO AVOID PERSONAL INJURY, COLUMN UPWARD TRAVEL SHOULD BE MAN- UALLY RESTRAINED TO CHECK UPWARD SPRING ASSISTANCE. THIS IS ESPECIALLY IMPORTANT IF
THE STEERING WHEEL HAS BEEN REMOVED FOR MAINTENANCE REASONS.
WARNING: ALL TYPES; DO NOT REMOVE THE STEERING COLUMN FROM THE VEHICLE WITH THE STEERING
WHEEL ATTACHED UNLESS THE STEERING
IS CENTERED AND THE COLUMN LOCK IS ENGAGED. IFTHE
SERVE THIS MAY RESULT IN AN INOPERATIVE AIRBAG SYSTEM. SEE LABEL ON STEERING WHEEL
HUB. LOCK IS TO BE RENEWED, 'LOCK-WIRE THE ASSEMBLY TO PREVENT ROTATION. FAILURE TO OB-
0
X300 VSM 1 Issue 1 August 1994
J57-27L
3 Ignition switch 1 1 Tilt motor 2 Tilt motor flexible coupling 4 Reach motor
Fig.
1 Major components Power operated steering column
Page 204 of 521
10.2 SERVICE
PROCEDURES - SAFETY RELATED
10.2.1
Airbag
The electrically activated driver's side airbag is attached to the steering wheel hub and is fed by two wires from the
column stalk assembly. Electrical input to the column stalk assembly for the airbag is provided by a dedicated harness
which is encased in a yellow sleeve. A mechanism in the stalk assembly called the 'cable reel cassette' provides conti
-
nuity from the static column to the steering wheel. The 'cable reel cassette' is driven by a tang which locates in the
steering wheel. Because the connection is by wires, and the cassette assembly is only capable of approximately five
(5) full turns,
it is critically important that initial positioning is correct, see Section 15. It is equally important that fitting of the steering wheel, connection of the column, lower shaft and steering rackshould
ONLY be made with the steering rack in the center of its travel.
WARNING: DO NOT REMOVE THE STEERING COLUMN FROM THE VEHICLE WITH THE STEERING WHEEL AT- TACHED UNLESS THE STEERING IS CENTERED AND THE COLUMN LOCK IS ENGAGED. IF THE LOCK
BARREL
IS TO BE RENEWED, 'LOCK-WIRE THE ASSEMBLY TO PREVENT ROTATION. FAILURE TO OB- SERVE THIS AND CONSEQUENT DAMAGE TO THE 'CABLE REEL CASSETTE MAY RESULT IN AN INOP- ERATIVE AIRBAG SYSTEM. SEE LABEL ON STEERING WHEEL HUB.
10.3 SERVICE PROCEDURES
10.3.1 Working Practices
It is not recommended that either the steering rack or engine driven pump assemblies are repaired in any way other
than in accordance with the repair procedures described in this manual. The fluid reservoir and filter is a disposable
assembly and no attempt should be made to clean it internally. Genuine replacement units must be fitted following
routine service or diagnostic confirmation of the failure of any component.
The importance of cleanliness cannot be over
-stressed, not only with new parts but also those which may havefailed.
In-service contamination of the hydraulic system is a major cause of failures and may be avoided with good working
practices and care. All new units and pipes must be supplied with suitable blanks in every orifice. Should a unit not
have blanks fitted, do not use
it - return it to the supplier with an appropriate reason for your action.
To help the manufacturer diagnose problems and avoid post-removal contamination; provide full details of the fault
and plug all connections as soon as they are released. All suspect units must be returned to Jaguar Cars complete
with relevant documentation.
CAUTION: It is imperative that the power steering system does not become contaminated in any way. Always de- cant fluid from afresh sealed container and clean the area around the reservoir neck both before and after topping-up. Never return drained fluid to the system.
10.3.2
Position the vehicle on a level surface with the engine sta- tionary and fluid cold. Add fluid, if required, so that the level
falls BETWEEN the marks
Fig.1.
10.3.3 System Bleed (following maintenance)
To avoid fluid aeration and possible pump damage, the in- itial fill process must be carried out with the ignition OFF.
Set the fluid level approximately 20 mm above the upper
dipstick level, and cycle the steering no less than three (3) times from lock to lock (this may be best achieved with the
front wheels off the ground). As air is expelled thefluid level
will fall, the level should be corrected. Start the engine and
further cycle thesteering until the fluid level becomes stable.
Stop the engine and finally set the level in accordance
with the fluid level check procedure.
10.3.4 Fluid Reservoir
The reservoir has an integral, non-serviceable, return-side
filter. Should any component be renewed or the system
'broken into' for any reason,
it is essential that the reservoir and the fluid are changed. Under normal operating condi- tions it is not necessary to change the fluid.
10.3.5 Hydraulic Connections
Fluid
Level Check and
Top-up
Jf7-281
Fig. 1
All hydraulic connections and surrounding areas should be scrupulously cleaned before and after work. Please note
that the steering rack valve block connections for FEED and RETURN are common in size. Ensure that the pipes are
correctly fitted, the uppermost one being the high pressure FEEDfrom the steering pump and the lower (RETURN) hav- ing a double depth hexagon tube nut.
X300 VSM 5 issue 1 August 1994
Page 205 of 521
@ Steering
Cause
Fluid level low?
Drive belt slack
(V12)
Pump drive loose (6cyl)
center pressures low
Air in system due to loose connection
Pump shaft seal faulty (fluid loss)
Delivery pressure or flow too low
Return flow restricted by blocked reser
-
voir filter
Both check valves blocked
Rack damper too
tight
Lower column incorrectly set
Excessive upper column friction
Faulty rotary valve or seal
Drive belt slack
(VI217
Engine idle speed too low
Pump drive loose
(6cyl)
Air in system due to loose connection
Pump shaft seal faulty (fluid
loss)
Delivery pressure or flow too low
Fluid level low?
tire pressures
high
Air in system due to loose connection
Stiff or seized steering joint
Rack damper too tight
Castor or tracking error
Lower column over extended
Fluid level low?
Air
in system due to loose connection
Pump shaft seal faulty (fluid
loss)
Rack damper loose
Pinion bearing faulty
Rack or column fixings loose
Rack mounting bracket loose
Rack mounting bush loose
Free play in column assembly
10.4 DIAGNOSTIC PROCEDURE
10.4.1 Introduction
The following diagnostic procedures are provided to rapidly pin-point mechanical faults which are not interrogated
by electrical means. Diagnostic procedures which require dedicated electrically operated equipment are dealt with in the 'Electrical Diagnostic Manual' (EDM) but may be mentioned here for reference.
10.4.2 Preliminary Action
Before any problem solving is undertaken it is essential that the fluid level and where applicable, belt tension, is
checked and if required corrected.
CAUTION: It is imperative that the power steering system does not become contaminated in any way. Always de cant fluid from a fresh sealed container and clean the area around the reservoir neck both before and after
topping-up. Never return drained fluid to the system.
10.4.2 Diagnostic Chart 1
Remedy
Rectify fluid loss and or top up
Re
-tension belt
Renew pump
Set to specification
Secure connection and bleed air out
Renew pump
Renew pump
Renew reservoir
Renew rack
Renew rack
Set to specification
Renew upper column
Renew rack
Retension belt
Reset idle speed
Renew
pump
Secure connection and bleed air out
Renew
pump
Renew pump
Rectify
fluid loss and or top up
Set to specification
Secure connection and bleed air out
Test and renew faulty joint
Renew rack
Check geometry and rectify
if required
Set to specification
Rectify fluid
loss and or top up
Secure connection and bleed air out
Renew pump
Renew rack
Renew rack
Tighten to specification
Renew rack
Renew rack
Check and rectify as required
Trouble
Heavy on both sides
Heavy on one side
Heavy when steering
rapidly
Vague feel about center
Knocking
1 vibration felt
at steering wheel
0
0
0
0
Issue 1 August 1994 6 X300 VSM
Page 224 of 521
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
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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
Page 229 of 521
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