brake sensor LAND ROVER DISCOVERY 2002 Repair Manual

RESTRAINT SYSTEMS
DESCRIPTION AND OPERATION 75-9
Operation - SRS
The diagnostic and control unit (DCU) controls the SRS system. The DCU is located beneath the centre console close
to the handbrake area. The DCU contains both an electronic deceleration sensor as well as an electromechanical
safing sensor. When the electronic deceleration sensor within the DCU detects rapid deceleration of the vehicle, it
compares the deceleration rate with stored values in its' memory. If the deceleration rate exceeds the stored value
and the electromechanical safing sensor triggers, the DCU deploys the airbag and the seat belt pretensioners. The
DCU will not deploy the airbags and seat belt pretensioners unless both sensors trigger.
The SRS has diagnostic capabilities through TestBook. In the event that a fault is detected, the DCU alerts the driver
by illuminating a warning lamp in the instrument cluster.
The DCU controls the following:
lSRS warning lamp.
lDrivers airbag module.
lPassenger airbag module (where fitted).
lDriver seat belt pretensioner.
lPassenger seat belt pretensioner.
WARNING: The integrity of the SRS system are critical for safety reasons. Ensure the following precautions
are always adhered to:
lNever install used SRS components from another vehicle or attempt to repair an SRS component.
lWhen repairing an SRS system only use genuine new parts.
lNever apply electrical power to an SRS component unless instructed to do so as part of an approved test
procedure.
lSpecial Torx bolts are necessary for installing the airbag module - do not use other bolts. Ensure bolts
are tightened to the correct torque.
lAlways use new fixings when replacing an SRS component.
lEnsure the SRS Diagnostic Control Unit (DCU) is always installed correctly. There must not be any gap
between the DCU and the bracket to which it is mounted. An incorrectly mounted DCU could cause the
system to malfunction.
System deployment
The airbag and seat belt pretensioners deploy to protect the front seat occupants when the DCU senses a rapid
vehicle deceleration. The system deploys when the following conditions are met:
lThe ignition switch is on.
lThe vehicle decelerates beyond a threshold defined within the DCU.
lThe electromechanical safing sensor within the DCU triggers.
When all of the above conditions are met, the DCU deploys the airbag(s) and seat belt pretensioners. If the above
conditions are not met, the DCU will not deploy the system.
Component replacement policy
After an impact which deploys the airbags and pretensioners, the following components must be renewed:
lDCU.
lDriver and passenger airbag modules.
lDriver and passenger buckle pretensioners.
lRotary coupler.
lFlyleads (where applicable) connecting airbags and pre-tensioners to SRS harness

HARNESSES
REPAIRS 86-7-19
24.Disconnect 3 multiplugs from chassis harness.
25.Remove RH front indicator repeater lamp from
wing.
26.Disconnect multiplug from repeater lamp.
27.Remove repeater lamp.
28.Attach draw string to indicator lamp harness.
29.Withdraw harness to fuse box.
30.Remove draw string and secure.31.Disconnect main harness multiplug from
engine harness and ABS sensor.
32.Disconnect multiplugs from cruise control
actuator and brake fluid level switch.
33.Withdraw harness to bulkhead.

HARNESSES
86-7-28 REPAIRS
18.Secure multiplugs to steering column support
bracket and connect brake and clutch pedal
multiplugs.
19.Connect multiplugs to column switch and
passive coil.
20.Position passenger compartment fusebox,
connect multiplugs, fit fusebox to fascia and
secure with nut.
21.Connect ignition switch multiplug to fuse box.
22.With assistance feed LH side of harness into
engine bay.
23.Connect multiplugs to front door harness and
body harness.
24.Position earth headers to LH lower 'A' post and
secure with nuts.
25.Connect multiplugs to ECU pack.
26.Position harness in engine bay.
27.Connect and secure heated front screen
multiplugs.
28.Fit plenum molding.

+ HEATING AND VENTILATION,
REPAIRS, Plenum Air Intake.
29.Connect multiplugs to ABS sensor and fuel
cut-off switch.
30.Using draw string feed harness through inner
wing, remove draw string, connect repeater
lamp multiplug and fit lamp.
31.Connect multiplugs to ABS modulator.
32.Feed harness through to front panel.
33.Position body earth leads and secure with
bolts.
34.Connect washer reservoir multiplugs and
pipes, secure pipes with clips.
35.Secure fog lamp multiplug.
36.Secure earth header behind headlamp.
37.Connect multiplugs to headlamp level motor,
headlamp and side lamp.
38.Fit indicator lamp

+ LIGHTING, REPAIRS, Lamp - front
repeater.
39.Connect multiplug to LH horn.
40.Feed harness to ACE accelerometer, connect
multiplug and secure with cable ties.
41.Connect cruise control, ABS sensor and brake
fluid level switch multiplugs.
42.Connect engine harness multiplug and feed
harness along RH wing to fuse box.
43.Using draw string pull harness through inner
wing, remove draw string, connect repeater
lamp multiplug and fit lamp. 44.Connect chassis harness multiplugs.
45.Position engine bay fuse box and connect
multiplugs, fit fuse box and secure with screws.
46.Connect multiplugs to front of fuse box.
47.Position battery and starter cables and secure
with screws.
48.Fit fuse box cover.
49.Position earth lead and secure with nut.
50.Feed harness through to front panel.
51.Secure fog lamp multiplug.
52.Connect headlamp level motor, headlamp and
side lamp multiplugs.
53.Fit indicator lamp.

+ LIGHTING, REPAIRS, Lamp - front
repeater.
54.Secure harness to RH front panel.
55.Connect cooling fan and horn multiplug.
56.Secure harness to lower support rail.
57.Connect receiver drier and air temperature
sensor multiplugs.
58.Fit front bumper.

+ EXTERIOR FITTINGS, REPAIRS,
Bumper assembly - front.
59.Fit battery tray.
60.Fit air filter assembly.

+ ENGINE MANAGEMENT SYSTEM -
V8, REPAIRS, Air cleaner assembly.
61.Position both lower 'A' post trims and secure
with studs.
62.Fit heater assembly.

+ HEATING AND VENTILATION,
REPAIRS, Heater assembly - models with
air conditioning.

+ HEATING AND VENTILATION,
REPAIRS, Heater assembly - models
without air conditioning.

INSTRUMENTS
88-2 DESCRIPTION AND OPERATION
Instrument component location - Engine
compartment / underneath vehicle
1ECM (diesel models)
2Alternator
3Glow plugs
4Transmission temperature sensor
5Water in fuel filter sensor
6Fuel tank sender unit
7Differential lock switch – vehicles up to 03
model year8Differential lock switches – vehicles from 03
model year (where fitted)
9Parking brake switch
10Brake fluid level switch
11Oil pressure switch

INSTRUMENTS
88-4 DESCRIPTION AND OPERATION
Instrument block diagram
1Instrument pack
2ECM
3Brake fluid level switch
4Parking brake switch
5Oil pressure switch
6Alternator
7Fuel tank sender unit
8Water in fuel filter sensor
9Transmission temperature sensor
10Differential lock switch - vehicles up to 03
model year or Differential lock switches -
vehicles from 03 model year11Audible warning speaker
12SRS DCU
13SLABS ECU
14BCU
15ACE ECU
16EAT ECU
17Diagnostic connector
18Serial communications link