sensor LAND ROVER DISCOVERY 1999 Workshop Manual

STEERING
57-22 ADJUSTMENTS
38.Fit new seal, connect PAS cooler pipe and
tighten union nut to 24 Nm (18 lbf ft).
39. LHD only: Fit turbocharger intercooler feed
pipe and vacuum connection. Fit new seal to air
cleaner. Connect air intake hose and secure
clips. Connect multiplug to MAF sensor.
40.Clean chassis and surrounding area.
41.Fit underbelly panel.

+ EXTERIOR FITTINGS, REPAIRS,
Panel - underbelly.
42.Remove adaptor and hose set from tool LRT-
57-041.
43.Check PAS fluid level.
44.Connect battery earth lead.
Power steering pressure check - V8 LHD
models
$% 57.90.10.01
Check
1.Disconnect battery earth lead.
2.Syphon PAS fluid from reservoir.
3.Raise front of vehicle and support on stands.
4.Turn steering on LH lock.
5.Remove 3 screws securing LH splash shield
and remove shield.
6.Release clip securing PAS pipes.
7.Position absorbent cloth to catch spillage.
8.Position container to collect PAS fluid spillage.

FRONT SUSPENSION
60-4 DESCRIPTION AND OPERATION
Description
General
The front suspension comprises two dampers and coil springs, two radius arms, a Panhard rod and an anti-roll bar.
The front axle provides the location points for the dampers, springs, radius arms and the Panhard rod.
The anti-roll bar assembly is an essential part of the front suspension. On vehicles without Active Cornering
Enhancement (ACE) a conventional 'passive' anti-roll bar is fitted. On vehicles fitted with the ACE system, a thicker
diameter anti-roll bar, known as a torsion bar, is used with an actuator at one end.

+ FRONT SUSPENSION, DESCRIPTION AND OPERATION, Description - ACE.
The hydraulic dampers and coil springs provide springing for each front wheel. The long travel dampers, springs and
radius arms provide maximum axle articulation and wheel travel for off-road driving. The front axle is controlled
longitudinally by two forged steel radius arms and transversely by a Panhard rod.
Radius arms
Each radius arm is manufactured from forged steel. Two bushes are pressed into the forward end of the radius arm.
The forward end of the radius arm is located in a fabricated bracket on the axle and secured through the bushes with
two bolts and nuts. A bush is pressed into the rear of the radius arm which is also located in a fabricated bracket on
each chassis longitudinal and secured through the bush with a bolt and nut.
The radius arms prevent longitudinal movement of the front axle and because of their length allow maximum axle
articulation. The stiffness of the bushes in each radius arm also contributes to the vehicle roll stiffness.
Each radius arm has a notch on its lower edge which provides location for the vehicle jack.
Dampers
Two conventional telescopic dampers are used to control body/axle movement. A turret is located on a bracket welded
to the chassis. The upper spring seat has four studs which pass through holes in the bracket and align with
corresponding holes in the turret. Four nuts are screwed onto the studs and secure the turret and upper spring seat
to the chassis.
A fabricated platform is welded to the axle. The platform has two captive nuts which provide for the attachment of the
damper. A lower spring seat is located on the platform. Each spring seat is handed and has a bracket which secures
the ABS sensor harness and the front brake hose.
Each damper is fitted with a bush at its upper end. The bush locates in the top of the turret and is secured with a cross
bolt. The lower attachment point for the damper is also fitted with a bush. This bush has a spindle through its centre
with a hole at each end. The spindle is seated on the lower spring seat and the axle platform and secured with two
bolts. The coil spring is fitted in a compressed state between the upper and lower spring seats and assists the damper
in controlling the body/axle movement. The upper and lower bushes are replaceable items.
Rubber bump stops are fitted to the chassis above each end of the axle. The bump stops are progressive in their
compression and prevent the axle from contacting the chassis in the event of maximum suspension travel being
reached. The bump stops revert to their original shape once the compression load has been removed from them.
The damper functions by restricting the flow of a hydraulic fluid through internal galleries within the damper body. A
chromium plated rod moves axially within the damper. As the rod moves, its movement is limited by the flow of fluid
through the galleries thus providing damping of undulations in the terrain. The damper rod is sealed at its exit point
from the body to maintain fluid within the unit and prevent the ingress of dirt and moisture. The seal also acts as a
wiper to keep the rod outer diameter clean. A plastic shroud protects the rod and slides over the body as the damper
moves. The coil spring aids the damper to extend after being compressed and also aids the damping process.

FRONT SUSPENSION
DESCRIPTION AND OPERATION 60-17
The actuator has a forked end which locates on the bush in the short arm and is secured with a bolt and nut. The
piston rod of the actuator locates through a hole in a cast boss on the long arm which is fitted with a special bush. A
shoulder on the piston rod seats in a hole in the bush and a locknut on the end of the piston rod secures the rod to
the long arm and bush.
The front torsion bar is attached to the front chassis cross member. Two rubber bushes are fitted to the torsion bar
and are located in clamp plates. The clamp plates are located in slots in the cross member and secured with bolts.
The rear torsion bar is attached to the tubular cross member at the rear section of the chassis. Two rubber bushes
are fitted to the torsion bar and are located in clamp plates. The clamp plates are located in fabricated brackets
attached to the tubular cross-member and secured with bolts.
Two anti-roll bar links are mounted on brackets on the front and rear axles. Each anti-roll bar link is fitted with a
spherical bearing at each end. One bearing is attached to the link at a 90° angle. The threaded shank of the bearing
is located through a hole in a bracket on the axle and secured with a locknut; a washer is installed on the threaded
shank between the bearing and the bracket. The second spherical bearing is attached in-line with the link and locates
in the torsion bar on the left hand side and the long arm on the right hand side. The front anti-roll bar links are longer
than the rear links and are not interchangeable.
Accelerometers
Two accelerometers are used for the ACE system. The upper accelerometer is mounted on a bracket, behind the
headlining adjacent to the rear view mirror and the sunroof ECU. The lower accelerometer is located on a bracket on
the inner sill panel under the RH front floor.
The lower accelerometer is the primary sensor used to measure lateral acceleration of the vehicle for roll control. The
upper accelerometer is used by the ECU for roll correction and fault detection in conjunction with the lower
accelerometer.
Each accelerometer is a solid state capacitive acceleration sensor and operates on a 5 V supply from the ECU. The
upper and lower sensors can measure acceleration in the range of ± 1.10 g and return an output to the ECU of
between 0.5 and 4.5 V.
Failures of an accelerometer are recorded by the ECU and can be retrieved using TestBook. A special tool is required
to remove and replace a sensor in the bracket.

FRONT SUSPENSION
60-18 DESCRIPTION AND OPERATION
ACE Electronic control unit (ECU)
1Body Control Unit (Ref. only)
2Bracket3ACE Electronic control unit
4Attachment nuts 3 off
The ACE ECU is mounted on a bracket behind the passenger glove box and is identified from the other ECU's by its
single electrical harness connector. The single 36 pin connector is located on the lower face of the ECU and mates
with a connector from the main harness. The connector supplies power, ground, signal and sensor information to/from
the ECU for control of the ACE system.
The ACE ECU receives a battery power supply from fuse 15 in the engine compartment fusebox via the ACE relay,
also located in the engine compartment fusebox. The ECU provides an earth path for the relay coil, energising the
coil and supplying power to the ECU.
An ignition on signal is supplied from the ignition switch via fuse 29 in the passenger compartment fusebox. The
ignition on signal provides an input to the ECU which tells the ECU that ignition has been selected on and initiates a
250 ms start time. The start time is used to prevent functions operating when software routines are being initialised.
The ignition on signal, when removed, tells the ECU that the ignition is off. The ECU will remain powered for thirty
seconds after the ignition is turned off. The thirty second period allows the ECU to store values and fault flags in the
memory. These values are read by the ECU when the next ignition on signal is received.
An engine speed signal is transmitted to the ECU from the Engine Control Module (ECM) as a pulsed digital signal.
The engine speed signal is used by the ACE ECU to detect that the engine is running and hydraulic pressure for ACE
system operation is available.
A road speed signal is transmitted to the ACE ECU as a pulsed digital signal from the Self-levelling/Anti-lock Braking
System (SLABS) ECU. The road speed signal is used by the ACE ECU for on and off-road roll compensation.
When reverse gear is selected, an input is received from the reverse lamp switch. When the ACE ECU detects that
reverse gear has been selected, the ACE system reverts to a 'locked bars' condition until reverse gear is disengaged.
The diagnostic connection allows diagnostic interrogation of the ACE ECU. The diagnostic socket allows diagnostic
equipment to be connected to interrogate the ACE ECU for fault codes.

FRONT SUSPENSION
60-20 DESCRIPTION AND OPERATION
Failure modes
Failures where the vehicle can still be driven safely are indicated by the ACE warning lamp illuminating continuously
with an amber colour. The amber warning lamp will remain illuminated until the ignition is turned off. For all faults the
warning lamp will only illuminate again if the fault is still present. Failures which require the driver to stop the vehicle
immediately are indicated by the ACE warning lamp flashing with a red colour and an audible warning. All faults are
recorded by the ACE ECU and can be retrieved with diagnostic equipment.
The following tables show the type of system failures and their effects on the system operation. Torsion bar 'floppy'
means that fluid is allowed to circulate freely through the system. With no pressure in the actuators the torsion bar will
have no effect on vehicle roll. 'Locked bars' means that all pump flow is directed through the valve block and returns
to the reservoir. Both DCV's close and fluid is trapped in the actuators but can flow from one actuator to the other via
the valve block. In this condition the torsion bar will perform similar to a conventional anti-roll bar, resisting roll but still
allowing the axles to articulate.
Acceleration sensors
Pressure transducer
Road speed signal
21 Pressure transducer (earth) Input
22 DCV 2 (earth) Input
23 DCV 1 (earth) Input
24 DCV 1 & 2 (supply) Output
25 Pressure control valve (earth) Input
26 Not used -
27 Pressure control valve (supply) Output
28 Main supply (+ V Batt) Input
29 to 31 Not used -
32 Main earth 2 -
33 Accelerometer - lower (signal) Input
34 Accelerometer - upper (signal) Input
35 Not used -
36 Warning lamp Output
Failure Effect
Valve stuck closed No ACE control
Short circuit - Ground No ACE control
Short circuit - VBatt No ACE control
Loose sensor Erractic ACE activity when driving in straight line
Failure Effect
Short circuit - VBatt Large sensor dead band - possible random
movements
Failure Effect
Open circuit No ACE control - 'Locked bars' condition
Short circuit - Ground No ACE control - 'Locked bars' condition
Short circuit - VBatt No ACE control - 'Locked bars' conditionPin No. Description Input/Output

FRONT SUSPENSION
60-28 REPAIRS
Ball joint - upper - steering knuckle
$% 60.15.02
CAUTION: Each ball joint can be replaced up to
three times before the axle yoke bore becomes
oversize. Before commencing work, thoroughly
clean surface of joint and check for yellow paint
marks approx. 12 mm (0.5 in) wide. If 3 marks are
found, the axle case must be renewed.
Remove
1.Remove steering knuckle.

+ FRONT SUSPENSION, REPAIRS,
Steering knuckle.
2.Support the chassis on stands.
3.Support the front axle on stands.
4.Remove 2 nuts securing anti-roll bar lower links
to front axle, use a 16 mm spanner to prevent
link joint from turning.
5.Remove 2 bolts securing each front damper to
axle.
6.Remove 8 bolts securing chassis crossmember
and remove crossmember.
7.Remove bolt securing brake hose and ABS
sensor harness bracket to axle.
8.Lower the front axle, release front spring from
damper and remove front spring.9.Fit tool LRT-54-008/22 to tool LRT-54-008.
10.Fit tool LRT-54-008/4 to tool LRT-54-008, and
secure with screw.
11.Fit tool LRT-54-008 with all attachments to
upper ball joint.
12.Fit tool LRT-54-008/5 to the top of the ball
joint.
13.Press upper ball joint from axle. When ram lead
screw reaches the end of its stroke, retract the
lead screw and screw the ram further into the
tool. Repeat the operation until the ball joint is
released from the axle.
14.Dismantle the tools.

FRONT SUSPENSION
60-32 REPAIRS
Road spring - front
$% 60.20.11
Remove
1.Raise front of vehicle.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
2.Support vehicle under chassis.
3.Remove front road wheels.
4.Support weight of front axle.
5.Remove 2 nuts securing anti-roll bar links to
front axle and disconnect links from axle.
6.Remove 2 bolts securing each damper to front
axle.
WARNING: Make sure the axle cannot move
when the damper is disconnected. The
damper limits the downward movement of
the axle. If the axle is not restrained,
disconnecting the damper will allow
unrestricted movement which may cause
personal injury or damage to equipment.
7.Lower front axle.
CAUTION: Ensure brake hoses and ABS
sensor harnesses are not damaged when
lowering front axle.
8.Release and remove front spring from damper.Refit
1.Clean front spring seats.
2.Position front spring, with close coil uppermost,
over damper and locate in cut out in lower
spring seat.
3.Ensure both front springs are correctly located
in spring seats and raise front axle. Fit bolts
securing both dampers to front axle and tighten
to 45 Nm (33 lbf.ft).
4.Ensure washer is in place on lower ball joint of
each anti-roll bar link, then connect lower ball
joints to axle. Tighten nuts to 100 Nm (74 lbf.ft).
5.Fit front road wheels and tighten nuts to 140
Nm (103 lbf.ft).
6.Remove stands and lower vehicle.

FRONT SUSPENSION
REPAIRS 60-33
Wheel hub
$% 60.25.01
Remove
1.Release ABS sensor harness grommet from
inner wing valance and disconnect multiplug.
2.Raise front of vehicle.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
3.Remove road wheel.
4.Pull ABS sensor harness through aperture into
wheel arch.5.Release harness from brackets on inner wing
valance, suspension turret and front hub.
6.Release stake from drive shaft nut.
7.With assistance, remove drive shaft nut.
Discard the nut.
8.Remove front brake disc.

+ BRAKES, REPAIRS, Brake disc -
front.
9.Remove 4 bolts securing wheel hub to steering
knuckle.
10.Release wheel hub from steering knuckle, then
remove wheel hub and drive shaft assembly
from axle.
CAUTION: Do NOT remove the ABS sensor
from the hub. The hub and the sensor are
supplied as an assembly.

FRONT SUSPENSION
60-34 REPAIRS
11.Position the wheel hub and drive shaft on a
press, place supports beneath the wheel studs
and press the drive shaft from the wheel hub.
12.Remove drive shaft oil seal from axle casing. Refit
1.Clean drive shaft oil seal recess, drive shaft
splines, oil seal running surface, wheel hub
and steering knuckle mating faces, ABS
sensor and sensor recess.
2.Lubricate lip of new drive shaft oil seal and
running surface on drive shaft with clean
differential oil.

+ CAPACITIES, FLUIDS,
LUBRICANTS AND SEALANTS,
Lubrication.
3.Use tool LRT-51-012 to fit new drive shaft oil
seal to axle casing.
4.Fit drive shaft to axle casing.
5.Apply anti-seize compound to wheel hub and
steering knuckle mating face.
M51 0057

FRONT SUSPENSION
REPAIRS 60-35
6.Apply a 3 mm (0.125 in) wide bead of sealant,
Part No. STC 50554 around drive shaft
circumference, as illustrated.
7.Ensure ABS harness is located in cut out in
steering knuckle.
8.Fit wheel hub to drive shaft and align steering
knuckle. The sealant will smear along the
length of the splines as the wheel hub is fitted
to the drive shaft.
9.Fit wheel hub bolts and tighten to 100 Nm (74
lbf.ft).
10.Fit new drive shaft nut and lightly tighten.
11.Fit front brake disc.

+ BRAKES, REPAIRS, Brake disc -
front.
12.With assistance, final tighten drive shaft nut to
490 Nm (360 lbf.ft). Stake drive shaft nut. The
drive shaft nut must be tightened before
sealant has cured.
13.Secure ABS sensor harness to brackets and
secure grommet to inner wing.
14.Fit road wheel and tighten nuts to 140 Nm (103
lbf.ft).
15.Remove stand(s) and lower vehicle.
16.Connect ABS sensor multiplug.
Damper - front
$% 60.30.02
Remove
1.Raise front of vehicle.
WARNING: Do not work on or under a
vehicle supported only by a jack. Always
support the vehicle on safety stands.
2.Remove road wheel.
3. RH damper: Release coolant reservoir and
position aside.
4.Loosen through bolt securing damper to turret.
WARNING: Make sure the axle cannot move
when the damper is disconnected. The
damper limits the downward movement of
the axle. If the axle is not restrained,
disconnecting the damper will allow
unrestricted movement which may cause
personal injury or damage to equipment.
M51 0058