1995 LAND ROVER DISCOVERY relay

CRUISE CONTROL
1
DESCRIPTION AND OPERATION CRUISE CONTROL COMPONENT LOCATIONS -
Tdi AUTO EDC
COMPONENT LOCATION
1. Cruise control unit Under LH dash...................................................
2. Engagement (on/off) switch Dash panel....................................
3. Cruise control switch Steering wheel...............................................
4. Rotary coupler Steering wheel.........................................................
5. Vacuum pump Box section under jack.........................................................
6. Brake/vent switch Brake pedal....................................................
7. Vehicle speed sensor Transfer box behind transmission brake..............................................
8. Neutral lock-out relay Behind RH lower 'A' post trim casing..............................................
9. Actuator RH engine compartment...................................................................

19FUEL SYSTEM
2
DESCRIPTION AND OPERATION CRUISE CONTROL SYSTEM - V8i/Tdi AUTO EDC
Description
The cruise control system consists of
electro-mechanical devices, and comprises of the
following components.
ELECTRONIC CONTROL UNIT (ECU)
The microprocessor based ECU evaluates the signals
provided by the driver controls, brake pedal switch,
clutch pedal switch on manual models, and the
vehicle speed sensor. The ECU activates the vacuum
pump as required. The ECU also has a memory
function for set speed storage.
Driver operated switches
The main cruise control switch is located in the
auxiliary switch panel and activates the cruise control
system. The steering wheel switches provide
'set/accelerate' and 'resume/decelerate' features.
These switches provide the interface between driver
and cruise control system.
Brake pedal switch
The brake pedal switch is located under the lower
dash attached to the brake pedal mounting bracket.
The switch provides for fast disengagement of the
cruise control system and rapid return of the throttle
levers to the idle position when the brake pedal is
applied.
Clutch pedal switch
The clutch pedal switch is located under the lower
dash attached to the clutch pedal mounting bracket.
The switch provides for fast disengagement of the
cruise control system and rapid return of the throttle
levers to the idle position when the clutch pedal is
applied.Vehicle speed sensor
The vehicle speed sensor is located on the side of the
transfer box adjacent to park brake. The sensor
provides road speed data to the ECU. The cruise
control system cannot be engaged until the road
speed exceeds 45 km/h, (28 mph) the system will
automatically disengage at a road speed of 42 km/h
(26 mph).
Vacuum pump
The vacuum pump is energised when the main cruise
control switch is operated, and is actuated by the
steering wheel and brake pedal switches. The pump
provides a vacuum source to the cruise control
actuator. A control valve in the pump provides for
steady increase of road speed or purge of the system
when the brake pedal is applied.
Actuator
The actuator provides the servo mechanism link
between the cruise control system and throttle linkage
and is operated by vacuum from the vacuum pump.
Neutral lockout relay - automatic vehicles
The relay module is located in the right hand side
footwell, accessible by removing the trim casing.
The function of the relay module is to disengage the
cruise control system if neutral, or park, is selected in
the main gearbox, when the system is engaged.
Engine speed trip ECU - Manual vehicles
This unit is located in the right hand side footwell,
accessible by removing the trim casing.
The function of the unit is to disengage cruise control
if engine speed exceeds 5000 rev/min.

CRUISE CONTROL
7
REPAIR CRUISE CONTROL ECU - V8i
Service repair no - 19.75.49
Remove
1.Remove lower dash panel.
2.Disconnect ECU multi-plug.
3.Remove ECU fixing.
4.Remove ECU.
5.Reverse removal procedure. Ensuring that
electrical multi-plug is securely reconnected.
SPEED TRIP ECU - MANUAL V8i
NOTE: The neutral lock out relay
module/speed trip ECU is mounted in the
right hand side footwell. To identify
components.
See Electrical Trouble Shooting
Manual.
VEHICLE SPEED SENSOR
Service repair no - 18.30.22
For Tdi
See FUEL SYSTEM Tdi, Repair, Vehicle
Speed Sensor
For V8iSee FUEL SYSTEM MFI, Repair, Vehicle
Speed Sensor
NEUTRAL LOCK OUT RELAY
Service repair no - 19.75.28
1.Remove 3 studs securing fascia right hand side
closing panel.
2.Release and move closing panel aside.
3.Remove 2 studs securing right hand side 'A' post
lower trim casing.
4.Remove casing.
5.Locate relay (neutral coloured base) and release
base from bracket.
6.Remove relay.
NOTE: For further information.See
Electrical Trouble Shooting Manual.
Refit
7.Reverse removal procedure.

CRUISE CONTROL
9
REPAIR CRUISE CONTROL ECU - Tdi
Service repair no - 19.75.49
Remove
1.Remove 4 studs securing fascia left hand
closing panel.
2.Remove closing panel.
3.Remove nut securing ECU/relay bracket.
4.Lower bracket for access.
5.Remove bottom nut securing ECU to bracket.
6.Open glove box, align stops with cut-outs in
fascia panel and lower.
7.Move SRS harness aside.
8.Remove top nut securing ECU to bracket.
9.Disconnect ECU multiplug.
10.Remove ECU.
Refit
11.Reverse removal procedure. Ensure electrical
multiplug is securely reconnected.

BRAKES
3
DESCRIPTION AND OPERATION Description of components
1. ABS Modulator unit
To provide the ABS function a Modulator is positioned
within the system between the master cylinder and the
calipers. On both LHD and RHD vehicles it is sited on
the left inner wing [fender]. The Modulator has 8
solenoid valves, 2 for each wheel, 2 expanders and a
recirculation pump. It is non serviceable.
2. Servo/master cylinder
Actuation of the system is provided by a combined
master cylinder and servo assembly attached to the
pedal box, this provides pressure to opposed piston
calipers at each brake pad Twin piston at the front
axle, single piston at the rear.
3. Pressure reducing valve
To maintain the braking balance, pressure to the rear
axle is regulated by a Pressure Reducing Valve (PRV)
This PRV is of the failure bypass type, allowing full
system pressure to the rear axle in the event of a front
circuit failure. It is sited on the left inner wing [fender].
4. Electronic control unit - ECU
ABS control is provided by an electronic control unit
which is positioned on the passenger side of the
vehicle behind the dash panel/glove box.
The ECU, which is non-serviceable, is connected to
the ABS harness by a 35 way connector. non
serviceable.
The ECU continually monitors the brake system,
providing diagnostics in the event of a system
malfunction. Details of how to access the ECU
diagnostics are provided in the Electrical
Troubleshooting Manual.
5.& 6. Front and rear sensors/exciter rings - 4 off
A sensor is sited at each wheel, sensing a 60 tooth
exciter ring. When vehicle is in motion inductive
sensors send signals to ECU. Front exciter ring is
fitted to outside diameter of constant velocity joint
inside each front hub assembly. The rear exciter ring
is bolted to the rear of each brake disc bell.7. Diagnostic plug connection
A diagnostic plug is located behind the dash. To the
left of the steering column on LHD vehicles. To the
right of the steering column on RHD vehicles. It is a 5
way blue connector.
The location and identification of ABS electrical relays
are given in the Electrical Troubleshooting Manual.
For location and identification of ABS electrical fuses.
See ELECTRICAL, Repair, Fuse Box - Interioror.
See ELECTRICAL, Repair, Fuse Box - Engine
Compartment
ANTI-LOCK BRAKE SYSTEM - ABS
Manufactured by WABCO
Introduction
The purpose of ABS is to prevent vehicle wheels
locking during brake application, thus maintaining
vehicle steerability and stability. This allows vehicle to
be steered whilst brakes are applied, even under
emergency conditions, and to avoid obstacles where
there is sufficient space to redirect the vehicle.
WARNING: ABS is an aid to retaining
steering control and stability while
braking.
·ABS cannot defy the natural laws of physics
acting on the vehicle.
·ABS will not prevent accidents resulting from
excessive cornering speeds, following
another vehicle too closely or aquaplaning,
i.e. where a layer of water prevents adequate
contact between tyre and road surface.
·The additional control provided by ABS must
never be exploited in a dangerous or
reckless manner which could jeopardise the
safety of driver or other road users.
·The fitting of ABS does not imply that the
vehicle will always stop in a shorter stopping
distance.

70BRAKES
4
DESCRIPTION AND OPERATION System description
The brake system consists of dual hydraulic circuits in
a front - rear split. That is individual circuits to front
and rear axles.
Wheelspeed signals are provided by the fitting of
exciter rings to axles and speed sensors.
An ABS stop light switch is fitted to provide a braking
signal to the ECU as well as operate the stop lights.
Electrical wiring is provided as necessary with system
relays and fuses. Discovery Electrical Troubleshooting
Manual gives the location and wiring circuits of these
components.
Visual warning of system malfunction is provided via a
warning light in the instrument panel.
Hydraulic circuit ABS
Key
A = Primary hydraulic circuit
B = Secondary hydraulic circuit
C = Pressure reducing valve
D = ABS ModulatorABS System operation
During normal braking the feel of the brake pedal on
vehicles equipped with ABS will be the same as that
on non ABS vehicles. During ABS cycling the driver
will experience feedback in the form of a pulsating
brake pedal and solenoid/pump motor noise from the
Modulator.
The system is fully automatic in operation both on and
off road, and will only act when the ECU detects that
ABS cycling is necessary. The ECU continually
monitors the operation of the system.
When starting the ABS system will go through a series
of self checks, including a check of the solenoid
valves/pump motor.
WARNING LIGHT
The warning light will be on during the self check
(1.3-2 secs). If no faults are stored in the memory the
light goes out for 0.5sec,then comes on again. It will
then remain on until the vehicle is driven faster than 7
kph/5mph. This is the only time that the light will be on
without indicating a problem.
Any faults detected by the ECU will cause the warning
light to illuminate indicating that the vehicle may not
have full ABS control.

BRAKES
1
FAULT DIAGNOSIS ABS FAULT DIAGNOSIS
If a fault has occurred, or has been identified by ECU
self diagnostic function and ABS warning light is
illuminated. The system and components must be
checked to locate and rectify fault, using Testbook
diagnostics.
NOTE: If warning lamp has indicated a
fault in system, and no fault code has been
stored in memory, cause of fault is:
a) Failure in electrical supply
b) Bad ECU ground
c) Faulty warning light relay
d) ECU not connected
Before commencing fault diagnosis procedure
following items must be checked:
1.Inspect all exposed cables for damage or
abrasion.
2.Check ground on ABS system.
3.Battery - state of charge.
4.Check hub end-float.
5.All ABS fuses and electrical connections.
Fault rectification
1.Complete harness should be replaced if faults
are found in wiring harness.
2.DO NOT use unspecified cables or connectors,
as this could jeopardise safe function of ABS.
3.DO NOT attempt to open sealed 35 way
connector to ECU.FAULT DIAGNOSIS PROCEDURE
NOTE: If ABS warning light illuminates due
to large sensor air gap, fault will be
retained by the ECU memory. Where wheel
sensors have been pushed fully home prior to
test, The ECU will indicate a fault that has been
rectified.
NOTE: After any steering adjustment,
bearing replacement/adjustment, brake
disc replacement: Check hub end-float and
sensor clearance.
RELAYS AND FUSES ABS
The location and identification of ABS electrical relays
are given in the Electrical Troubleshooting Manual
For location and identification of ABS electrical fuses.
See ELECTRICAL, Repair, Fuse Box - Interioror.
See ELECTRICAL, Repair, Fuse Box - Engine
Compartment

70BRAKES
22
REPAIR MODULATOR UNIT
Service repair no - 70.65.45
WARNING: New modulator units are
supplied in a shock absorbing pack
marked with a use by date. The new
modulator will contain hydraulic brake fluid within
the valve block and all ports plugged.
Modulator units must be handled with care the
following must be avoided:- any impact, use of
compressed air on any of the hydraulic ports,
removing plugs to connection ports before fitting
unit.
Remove
1.Refer to the illustration of brake components
ABS. For details of modulator unit and hydraulic
pipe connections to it.
See Brake
Components ABS
2.Refer to general brake service practice.See
General Brake Service Practice
3.Check new modulator unit is packaged in
accordance with the WARNING above.
4.Disconnect battery negative lead.
5.Remove the two electrical plugs.
6.Identify 8 pipe to modulator connections for
correct reassembly.
7.Disconnect 8 pipe unions.
8.Remove nuts securing modulator to mounting
bracket.
9.Remove modulator unit.
10.Remove mounting bushes and cup.
Refit
11.Fit mounting bushes and cup to new modulator.
12.Fit modulator unit to mounting bracket.
13.Fit 8 pipes to modulator connections. Pipes
mustbe connected to correct port. Tighten to
15Nm.
14.Bleed the complete hydraulic system.See
Brake System Bleed
15.Check system function using the 'Testbook'
diagnostics
16.Test operation of brakes.ELECTRONIC CONTROL UNIT ABS
Service repair no - 70.65.01
Remove
For location of the ECU.
See Description and
operation, ABS Components
1.Disconnect battery negative lead.
2.Remove retaining bolt and lower alarm system
ECU and relay mounting bracket into passenger
footwell.
3.Remove two screws and detach ECU complete
with harness plug from mounting bracket.
4.Release ECU plug retaining clip.
5.Move plug in direction of arrow and release
hooked end of plug from retaining post.
Refit
6.Reconnect ECU harness plug ensuring that it is
firmly located and retaining clip secures plug.
7.Reverse removal procedure.