bonnet LAND ROVER DISCOVERY 1999 Repair Manual

ALARM SYSTEM AND HORN
86-4-4 DESCRIPTION AND OPERATION
Alarm system block diagram
1Body Control Unit (BCU)
2Remote handset
3Receiver
4Fuel cut off switch
5Ignition switch
6Central door locking switch
7Volumetric sensors
8Bonnet activated alarm switch
9Drivers door key lock/unlock switches
10Door latch switches 11Fuel flap release switch
12Intelligent Driver Module (IDM)
13Battery Backed Up Sounder (BBUS)
14Alarm sounder
15Vehicle horns
16Direction indicators
17Door lock actuators
18Engine Control Module (ECM)
19Starter motor

ALARM SYSTEM AND HORN
DESCRIPTION AND OPERATION 86-4-9
Bonnet switch
The BCU uses a plunger type switch to determine if the bonnet has been forcibly opened when the alarm has been
set. The switch is located under the bonnet on the left hand side of the vehicle when viewed from the rear.
Input/Output
When the bonnet is closed the bonnet activated alarm switch is in an open condition and the input to the BCU is more
than 6 volts, in which case the BCU pulls the input high internally. When the bonnet is open the bonnet activated alarm
switch is closed and the input to the BCU is less than 2 volts.
The bonnet activated alarm switch has a dedicated signal input to the BCU. This allows the BCU to identify the
position of the bonnet.
TestBook provides the ability to monitor the real time state of the switch.

ALARM SYSTEM AND HORN
DESCRIPTION AND OPERATION 86-4-15
Vehicle horn/alarm sounder
Vehicle horn
Alarm sounder
Depending on system configuration, the alarm sounder will either sound independently or in conjunction with the
vehicle horns as an alarm triggered warning. The alarm sounder is located under the bonnet on the bulkhead. If the
alarm is triggered, the alarm sounder operates at 0.5 second intervals in phase with the direction indicators.
Input/Output
The BCU provides an earth path for the alarm sounder relay situated in the passenger compartment fuse box.
Fuse 21 supplies battery power to the alarm sounder relay. When an unauthorised entry to the vehicle is detected,
the BCU provides an earth path for the alarm sounder relay. This earth path energises the alarm sounder relay, which
activates the alarm sounder.
If a mislock occurs the BCU triggers the alarm sounder 2 times for a period of 50 ms on, 200 ms off.
The BCU triggers the alarm sounder once for a period of 50 ms when an EKA code is requested.
When the EKA code is entered correctly, the alarm sounder will operate twice for a period of 50 ms on, 200 ms off.
The alarm sounder relay has a dedicated signal to the BCU.

ALARM SYSTEM AND HORN
DESCRIPTION AND OPERATION 86-4-17
Operation
Standard system functions
All vehicles have the following functions as standard.
lLocking.
lUnlocking.
lFuel cut off switch unlocking.
lInternal locking.
lElectric fuel flap release.
Locking
The doors are locked by pressing the lock button on the handset or by locking the vehicle from the driver's door with
the key.
In order to lock the vehicle, the following conditions must be met:
lThe driver's door is closed.
lThe ignition is off.
lThe fuel cut off switch is not tripped.
lThe bonnet is closed.
lThe vehicle is not super locked.
Depending on system configuration a mislock occurs if these conditions are not met. The doors may lock (depending
on condition not met) and the system may not fully arm, depending on configuration of the system. If a mislock occurs
an audible warning is emitted and the vehicle becomes partially armed.
Unlocking
The doors are unlocked by pressing the unlock button on the handset or by unlocking the vehicle from the driver's
door with the key. This may unlock only the driver's door or it may unlock all doors depending on system configuration.
Fuel cut off switch unlocking
In the event that the vehicle experiences a force strong enough to actuate the switch, all the doors on the vehicle
immediately unlock. The following conditions must be met for this to occur:
lThe security system is not armed.
lThe ignition is on.
This same action causes the fuel pump to shut off and disables the Engine Control Module (ECM). In some markets,
this action may also cause the direction indicators lights to flash.

ALARM SYSTEM AND HORN
86-4-18 DESCRIPTION AND OPERATION
Internal locking
Internal locking allows the doors to be locked / unlocked from a central position using switches on the instrument
panel. The internal unlock switch will not operate if the vehicle is super locked.
Electric fuel flap release
Up to 03 model year shown
The fuel flap is opened by pressing the button on the fascia on vehicles up to 03 model year or on the instrument pack
binacle on vehicles from 03 model year. This works only if the anti-theft system is not armed and the ignition is off.
In some configurations, it may also be necessary to remove the key from the ignition switch.
Configurable system functions
The following alarm system features are configurable using TestBook.
lPerimetric alarm.
lVolumetric alarm.
lSuper locking.
lPartial arming.
lMislock.
lPassive immobilisation.
lPassive remobilisation.
lEmergency key access.
lSingle point entry.
lSpeed related locking.
lAcclimatisation related locking.
lVisual warnings.
lAudible warning.
lTheft deterrent led.
lTransit mode.
Perimetric alarm
The perimetric alarm is used by the BCU to detect unauthorised opening of a door or hinged panel. Switches
incorporated into the door latch assemblies and the bonnet determine the state of the panels.
There are two perimetric alarm configurations:
lAlarm not active.
lAlarm active.
Arming: To arm the perimetric alarm, press the lock button on the handset or lock the vehicle using the key in the
driver's door. Once the alarm has been set, the BCU monitors the state of the doors and the bonnet.
In order to arm the perimetric alarm the following conditions must be met:
lDrivers door closed.
lKey not inserted in ignition switch.
lFuel cut-off switch not tripped.

ALARM SYSTEM AND HORN
DESCRIPTION AND OPERATION 86-4-19
Disarming: To prevent the alarm from triggering when entering the vehicle, the alarm system must be disarmed with
the key or the handset.
There are two perimetric alarm disarming configurations:
lAlways disarm with key.
lOnly disarm with key if locked with key.
The perimetric alarm can be disarmed by unlocking the vehicle with the handset or by using the key in the driver's
door lock, depending on system configuration.
NOTE: The “only disarm with key if locked with key” configuration prevents the alarm from being disarmed by
unlocking the vehicle with the handset if the vehicle has been locked by the key. In this situation the Emergency Key
Access (EKA) code must be entered to disarm the alarm.
In order for the alarm to trigger, the following conditions must be met:
lPerimetric alarm armed.
lBonnet or door opened.
Once triggered, the alarm will remain triggered for 30 seconds before resetting.
Volumetric alarm
The volumetric alarm is used by the BCU to detect movement within the vehicle. This allows the alarm to be triggered
if a window is smashed in an attempt to gain access to the vehicle.
There are two volumetric alarm configurations:
lVolumetric alarm not active.
lVolumetric alarm active.
Two sensors, which transmit and receive ultrasonic signals, detect movement within the vehicle. Theses sensors
detect any change in air movement within the vehicle and then supply the BCU a signal to activate the alarm. Fifteen
seconds after the vehicle is locked with the handset or the key the volumetric alarm is armed. This delay is
incorporated into the BCU software to prevent accidental or nuisance triggering of the alarm.
In order to arm the volumetric alarm, the following conditions must be met:
lDriver's door closed.
lKey not inserted in ignition.
lFuel cut-off switch not tripped.
To prevent the alarm from triggering when entering the vehicle, the alarm system must be disarmed with the key or
the handset.
There are two volumetric alarm disarming configurations:
lAlways disarm with key.
lOnly disarm with key if locked with key.
The volumetric alarm can be disarmed by unlocking the driver's door with the key or the handset, depending on
system configuration.
NOTE: The “only disarm with key if locked with key” configuration prevents the alarm from being disarmed by
unlocking the vehicle with the handset if the vehicle has been locked by the key. In this situation the EKA code must
be entered to disarm the alarm.
In order for the alarm to trigger, the following conditions must be met:
lVolumetric alarm armed.
lVolumetric sensors triggered.
Once triggered, the alarm will remain triggered for 30 seconds before resetting.

ALARM SYSTEM AND HORN
86-4-20 DESCRIPTION AND OPERATION
Super locking
Super locking prevents the use of the interior door handles to unlock and open the vehicle doors. This prevents the
doors from being opened if the window be smashed in an attempt to gain access to the vehicle.
There are four configurations for super locking:
lNo super locking.
lSuper locking on single handset press only (no key activated super locking).
lSuper locking on single handset press or single key turn.
lSuper locking on double handset press or double key turn.
To super lock, press the lock button on the handset once or twice within one second depending on system
configuration. In some configurations, it is also possible to super lock the vehicle using the key in the driver's door.
This also may require one or two turns of the key in the lock direction. If two turns of the key are required to activate
super locking, the two turns must occur within one second of each other.
In order to super lock the vehicle, the following conditions must be met:
lAll door are closed.
lThe ignition is off.
lThe fuel cut-off switch is not tripped.
Partial arming
Partial arming allows protection of as much of the vehicle as possible if the alarm is armed with one or more doors or
the bonnet open.
Partial arming allows the vehicle alarm to be armed even if the following conditions exist. When the bonnet or door is
closed, the BCU activates the perimetric alarm and the volumetric alarm after 15 seconds have elapsed:
lThe bonnet is not closed: If the bonnet is open when the alarm is armed, the BCU activates super locking and
volumetric sensing. In this condition, the alarm enters a partially armed state. All other functions of the alarm are
active and the BCU monitors the bonnet for a change of state. If the bonnet closes, the system is completely
armed.
lThe passenger door, a rear door or the tail door is not closed: If a door is open when the alarm is armed, the BCU
does not activate super locking or volumetric sensing. In this condition the alarm enters a partially armed state.
All other alarm functions are armed and the BCU monitors the open door. If the door closes volumetric sensing
and super locking become active.
lFailure of a door latch switch: If a short circuit in the door latch switch occurs, the BCU presumes the door is not
closed. In this situation the BCU does not activate super locking or volumetric sensing. All other alarm functions
are armed.
lDamaged wiring harness: If a short circuit in the wiring harness for the door latch switch occurs, the BCU
presumes the door is not closed and does not activate super locking or volumetric sensing; all other alarm
functions are armed. If an open circuit in the wiring harness for the door latch switch occurs, the BCU presumes
the door is closed and arms the alarm as normal.
Mislock
Mislock alerts the driver that a failed attempt has been made to lock the vehicle because of the doors or the bonnet
not being fully closed.
There are six audible configurations for mislock:
lNo audible warning.
lAlarm sounder.
lVehicle horn.
lAlarm sounder and vehicle horn.
lBBUS.
lAlarm sounder, vehicle horn and BBUS.
When a failed attempt has been made to lock the vehicle, the audible warning device is switched on for 50 ms and
off for 200 ms. The BCU allows the audible warning device to operate 3 times.

ALARM SYSTEM AND HORN
REPAIR 86-4-27
Sounder - battery backed-up (BBUS)
$% 86.77.13
Remove
1.Remove rear quarter lower casing.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Trim casing - side - loadspace.
2.Remove nut securing BBUS to RH rear body
panel.
3.Disconnect multiplug and remove BBUS.
Refit
1.Position BBUS, connect multiplug and tighten
securing nut.
2.Fit rear quarter lower casing.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Trim casing - side - loadspace.
Switch - bonnet
$% 86.77.20
Remove
1.Remove rubber cover from bonnet switch.
2.Disconnect multiplug, release switch retainers
and remove switch.
Refit
1.Position switch and connect multiplug.
2.Fit rubber cover to switch,

HARNESSES
86-7-2 REPAIRS
5.Release and disconnect 4 multiplugs from LH
lower 'A' post.
6.Release clip and disconnect rear washer pipe
from LH lower 'A' post.
7.Release harness from behind bonnet release
cable.
8.Release harness from 4 retainers in LH upper
'A' post and collect protective sleeves. 9.Release 4 clips securing harness to centre of
roof.
10.Disconnect multiplug from ACE accelerometer.
11.Disconnect multiplug from interior mirror.
12.Feed harness through roof to upper 'A' post.
13.Release 3 retainers securing harness to RH
roof panel.
14.Release 2 cable clips securing body harness to
sunroof harness.

HARNESSES
REPAIRS 86-7-7
Refit
1.With assistance, position harness to air
conditioning ducting and secure with cable ties.
2.Secure harness to sunroof harness with cable
clips.
3.Connect multiplug to RF receiver.
4.Feed harness to LH and RH upper 'E' posts.
5.Feed harness through 'E' post to tail lamp and
rear bumper and secure with grommet.
6.Connect multiplug to fuel flap solenoid and
alarm sounder.
7.Position alarm sounder to rear quarter and
secure with nut to 9 Nm (7 lbf.ft).
8.Position both RH earth header to 'E' post and
tighten nut to 10 Nm (7 lbf.ft).
9.Feed tail door harness through 'E' post and
secure with grommet.
10.Position harness sleeve to outer edge of door
and pull harness through door.
11.Secure harness to tail door with clips.
12.Connect washer tube to rear of wiper arm.
13.Remove tape from draw string and secure to
CHMSL harness.
14.Draw harness through tail door and connect
Lucars to CHMSL.
15.Fit CHMSL cover and secure with screws.
16.Connect multiplug to door lock switch.
17.Connect Lucars to HRW.
18.Connect multiplug to rear wiper motor.
19.Connect multiplug to door latch.
20.Fit plastic sheet to tail door, ensuring it aligns
with witness marks.
21.Fit tail door trim casing.

+ DOORS, REPAIRS, Trim casing - tail
door.
22.Connect Lucar to radio aerial RH amplifier.
23.Secure harness to RH side of body with clips
and retainers.
24.Position both LH earth header to 'E' post and
tighten nut to 10 Nm (7 lbf.ft).
25.Connect multiplugs to both tail/flasher lamps
and secure harness to bumper with clips.
26.Fit both rear tail lamps.

+ LIGHTING, REPAIRS, Lamp - tail.
27.Secure harness to rear LH side of body with 6
cable clips.
28.Connect 2 Lucars to rear air conditioning unit.
29.Fit both luggage compartment trim casings.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Trim casing - side - loadspace.
30.Feed harness into position for rear interior light.
31.Connect Lucar to radio aerial LH amplifier.
32.Secure harness to body with cable ties clips
and retainers.
33.Secure air conditioning ducting to body with
rivets.
34.Feed harness to LH lower 'A' post. 35.Secure harness to LH side of body with cable
tie clips and retainers.
36.Connect and secure multiplugs to lower LH 'A'
post.
37.Feed harness through roof to centre.
38.Secure harness behind bonnet release cable.
39.Connect rear washer pipe at lower 'A' post and
secure with clip.
40.Secure harness to roof with clips.
41.Connect multiplug to interior mirror, ARC
accelerometer.
42.Position sound deadening panels and secure
with clips.
43.Fit headlining.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Headlining.
44.Fit fascia panel.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Fascia.