1999 LAND ROVER DISCOVERY horn

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-3
BCU outputs
The BCU processes the input signals it receives and uses the information to determine the control outputs that need
to be established for any given set of conditions. The BCU provides controlled outputs for the following systems:
lInterior courtesy lamps.
lFuel flap release actuator.
lAnti-theft status LED.
lEngine Control Module.
lDoor lock actuators.
lDirection indicators and hazard warning lamps.
lHeadlamps.
lAlarm sounder.
lVehicle horns.
lBattery backed sounder.
lStarter relay.
lPassive re-mobilisation exciter coil.
Simultaneous switching of outputs in different units is limited by the bus transfer time, but the skew is no longer than
100 ms for either the BCU or the IDM. When the processor is reset, all outputs are switched off until the inputs have
been read for the first time to check current condition.
BCU to harness connectors
1Connector C0661
2Connector C0662
3Connector C06634Connector C0660
5Connector C0664
The pinout details for the BCU connectors are defined below:

BODY CONTROL UNIT
86-3-6 DESCRIPTION AND OPERATION
C0662 connector pin details
Pin No. Description Input/Output
1 Front left window - down Input
2 Ignition key inserted Input
3 Rear wiper Input
4 Vehicle horns Input
5 Crank enable Output
6 Gear position switch (Y contacts) Input
7 CDL doors unlock Input
8 Rear fog lamps selected Input
9 Gear position switch (W contacts) Input
10 Drive selected (HDC) Output
11 Ignition key interlock solenoid Output
12 Headlamp powerwash Output
13 Gear position switch (X contacts) Input
14 Not used -
15 Transfer box - neutral selected Input
16 Seat buckle fastened Input

BODY CONTROL UNIT
86-3-12 DESCRIPTION AND OPERATION
Seatbelt warning lamp Timed The warning lamp is on for 6 seconds after the ignition is turned on.
Buckle The warning lamp is on for 6 seconds after ignition is turned on or until
the buckle is fastened.
Ignition II If the buckle is unfastened when the ignition is turned on then the
warning lamp comes on for 6 seconds.
Disable The warning lamp is not used.
Seatbelt audible warning Timed The audible warning is on for 6 seconds after the ignition is turned on.
Buckle The audible warning is on for 6 seconds after the ignition is turned on
or until the buckle is fastened.
Ignition II If the buckle is unfastened when the ignition is turned on then the
audible warning is on for 6 seconds.
Disable The audible warning is not used.
Bulb failure warning Disabled Direction indicator bulb failure detection is disabled.
Enabled Direction indicator bulb failure detection is enabled.
Superlocking None Superlocking is not available.
Double The vehicle will superlock on a double press of the remote transmitter
or double key turn.
Single The vehicle will superlock on a single press of the remote transmitter
or a single key turn.
No key The vehicle will superlock on a single press of the remote transmitter
but not with the key.
Door unlocking Not SPE The SPE (Single Point Entry) function is not used. All doors unlock on
a remote transmitter press.
SPE Only the driver's door unlocks on the first remote transmitter press, all
other doors on the second press.
Alarm disarming Always Operation of the key in the driver's door always disarms the vehicle.
Key only Operation of the key in the driver's door only disarms the vehicle if it
was locked with the key.
Key never The security system is not disarmed by the key (except for EKA).
Inertia switch No hazards Operation of the inertia switch does not operate the hazard warning
lamps.
Hazards Operation of the inertia switch operates the hazard warning lamps.
Speed locking Disabled Speed related locking is disabled.
Enabled Speed related locking is enabled. The door locks are disabled when
the vehicle is moving.
Volumetric sensing Disabled Volumetric sensing is disabled.
Enabled Volumetric sensing is enabled.
Alarm Disabled The vehicle is not fitted with a security system.
Enabled The vehicle is fitted with a security system.
Passive immobilisation Disabled Passive immobilisation is disabled.
Enabled Passive immobilisation is enabled.
Hazard warning lamps Disabled The hazard warning lamps do not flash on security system arm,
disarm or trigger.
Enabled The hazard warning lamps flash on security system trigger only.
All The hazards flash on security system arm, disarm and trigger.
Mislocking audible
warningDisabled Mislock audible warnings are disabled.
Enabled Mislock audible warnings are enabled.
Alarm sounder Alarm Audible warnings are given by the security system sounder only.
Both Audible warnings are given by both the security system sounder and
the vehicle horn.
Vehicle Audible warnings are given by the vehicle horn only.
BBUS Audible warnings are given by the security system sounder, vehicle
horn and BBUS.
Disabled Audible warnings are not given. Function Option Details

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-13
Anti-theft system
The BCU controls the logical switching operations for enabling and activating the anti-theft system. Features include:
lPerimetric protection – monitors the condition of doors and hinged panels.
lVolumetric protection – monitors the vehicle's interior space.
lRemote locking, superlocking and unlocking functions.
lEngine immobilisation and remobilisation.
lAdvanced mislock detection and automatic compensation.
lEKA code functions.
lCustomer configuration options.
lMarket configuration options.
Immobilisation
The immobilisation system comprises the following components:
lRF receiver.
lRF transmitter/ transponder.
lTransponder coil.
lBCU.
lDoor switches, door lock switches and bonnet switch.
lIDM.
lECM.
lStarter solenoid relay.
lStatus LED.
Alarm system
The alarm system comprises the following components:
lRF receiver.
lRF transmitter.
lBCU.
lIDM.
lDoor switches, door lock switches and bonnet switch.
lBattery backed-up sounder (BBUS).
lStatus LED.
On non NAS vehicles, power supply for the alarm sounder and the battery BBUS is provided through two relays in the
passenger compartment fuse box. Each of the coils of the alarm relays are directly connected to the IDM which
controls their operation under the direction of BCU signals received via the serial data bus.
On NAS vehicles, an audible warning is provided through operation of the vehicle horns. The BCU provides an earth
path for the coil of the horn relay to initiate vehicle horn operation.

+ ALARM SYSTEM AND HORN, DESCRIPTION AND OPERATION, Description.
Acclimatisation locking Disabled The vehicle cannot be locked if the ignition is on.
Enabled The vehicle can be locked if the ignition is on and the engine is
running.
Alarm tamper Disabled The security system LED does not flash when the security system has
been tampered with.
Enabled The security system LED flashes when the security system has been
tampered with.
Engine immobilised LED off The security system LED does not flash when the engine is
immobilised.
LED flash The security system LED flashes when the engine is immobilised.
Low battery warning Disabled The security system LED does not flash when the remote transmitter
battery is low.
Enabled The security system LED flashes when the remote transmitter battery
is low.
Emergency Key Access
(EKA)Disabled EKA is disabled.
Enabled EKA is enabled and the door locks operate electrically.
No unlock EKA is enabled, but the door locks do not operate electrically. Function Option Details

BODY CONTROL UNIT
DESCRIPTION AND OPERATION 86-3-19
Operation
For IDM inputs which are also inputs for BCU functions, the delay before the BCU recognises the change in input
status is less than 250 ms. The BCU uses a debounce algorithm to ignore changes in input having a duration less
than 100 ms with the exception of automatic gearbox W, X, Y, Z inputs, which have a debounce period of 33 ms.
Transit mode
To prevent excessive battery drain during transit to overseas markets, the vehicle is placed in a transit mode.
To exit the transit mode, simultaneously hold down the heated rear window switch and the rear fog lamp switch, turn
the ignition switch from 0 to II and, after a minimum of 2 seconds, release the switches.
Transit mode can be entered using TestBook. When TestBook communicates with the BCU for diagnostics related to
BCU operation, it first checks that the vehicle is not in transit mode.
Anti-theft system
The BCU uses the driver's door key lock and unlock switches to activate and deactivate the security system. The
driver's door lock is also used for entering the EKA.

+ ALARM SYSTEM AND HORN, DESCRIPTION AND OPERATION, Description.
Immobilisation
For immobilisation, the BCU disables the starter motor relay. When the engine is cranking, the ECM looks for a coded
signal from the BCU. If the signal is not received within one second of cranking, the fuel supply to the engine is
stopped and the injectors are disabled. This also prevents unburnt fuel from entering the catalyst.
If the BCU is disconnected, the engine starter motor will remain isolated by the starter motor relay and the ECM will
remain immobilised. The main wiring for the system is contained within the main harness which is relatively
inaccessible, so preventing intruders from disabling the system by cutting the wires for the immobilisation system.
Once the immobiliser has been activated, destruction of the trigger device or the wiring to it will not disarm the system.
The RF transmitter communicates to the BCU via the RF receiver using a 70 bit code. Pressing the unlock button on
the transmitter will re-mobilise the vehicle. The RF transponder is integrated into the metal key assembly, inserting
the key into the ignition switch will induce a signal in the exciter coil to re-mobilise the vehicle.
Anti-theft alarm
The alarm system provides a warning of unauthorised access to the vehicle and includes perimetric and volumetric
monitoring under the control of the BCU.
The perimetric protection system detects opening of all doors, tail door and bonnet and will also detect the operation
of the ignition key switch. The following conditions must be satisfied before the BCU will operate all of the functions
of perimetric protection:
lAll doors and hinged panels are in the closed position.
lIgnition key out of the ignition switch.
lInertia switch is not tripped.
If all conditions are not satisfied the BCU will enter a mislock condition.
The volumetric sensor uses two ultrasonic sensors mounted in the headlining to detect movement within the vehicle.
The alarm will trigger when the sensor signals the BCU for 200 ms or greater. Within a single setting period the alarm
system will allow a maximum of 10 triggers as a result of any combination of sensor inputs. It is possible to lock the
vehicle without enabling the volumetric alarm by using the key. The same conditions needed to satisfy enabling of the
perimetric protection system is also needed to enable volumetric protection.
When the alarm system is set the BCU checks the status of all the inputs from the door and bonnet switches to ensure
the integrity of the vehicle before setting the alarm system into operational mode. In some markets, when the alarm
is set the BCU sends a signal to the IDM which will cause the direction indicators to flash three times for a duration of
3 seconds.
If the sensors are triggered the BCU will activate an alarm sounder to provide an audible warning of a theft attempt.
The activation period of the alarm sounder is 25 to 30 seconds. The duty cycle of the alarm sounder is 50:50 ± 10%.

BODY CONTROL UNIT
86-3-20 DESCRIPTION AND OPERATION
In some markets, when the alarm is triggered the BCU also activates the direction indicators, in phase with the audible
warning, to provide an optical warning of a theft attempt. The activation period of the optical alarm is 25 to 30 seconds.
The duty cycle of the optical warning is 50:50 ± 10%.
The alarm system relies upon the vehicle battery for power. However, the BCU remembers the status of the security
system if it loses battery supply. If the security system was in a set condition when battery supply was lost the BCU
will trigger the alarm and initiate a visual warning by flashing the hazard lamps when the battery voltage is restored.
On vehicles with a BBUS fitted, the BBUS will sound if the battery is disconnected while the alarm system is set.
Door switches
The BCU uses the door latch switches to indicate if a door is open or closed. The BCU provides power to all door latch
switches; the switches are in the 'normally open' condition when the doors are shut. When a door is opened, the door
switch contacts are closed and the circuit is earthed, signalling a change in state to the BCU. All doors except the
driver's doors are connected in parallel, so the BCU will recognise a passenger door has been opened but will not be
able to distinguish which one. The driver's door has a dedicated signal line which enables the BCU to detect if the
driver's door has been opened or closed.
Door lock actuators
The CDL system has the facility to enable superlocking. All door lock actuators are controlled by the BCU via the IDM.
The driver's door is controlled separately from all other doors, enabling functions like single point entry and key
access.
Driver's door key lock and unlock switches
The BCU uses the driver's door key lock and unlock switches to activate and deactivate the security system. The
driver's door lock is also used for entering the EKA code.
Two separate switches are incorporated into the key lock assembly of the driver's door. The switches are normally
open and the BCU provides a separate power supply to each. The BCU is signalled when a circuit is earthed enabling
it to determine the direction in which the lock has been turned.
Bonnet switch
The bonnet switch is powered from the BCU and is used as a logical input for operation of the security system. The
switch is normally open with the bonnet closed, when the bonnet is opened the switch contacts close to complete a
circuit to earth and signal the change in state to the BCU.
Key-in sensor
When the ignition key is inserted into the lock barrel the key-in sensor contacts close and supply a signal to the BCU.
The BCU monitors the ignition switch for a change in state and triggers the alarm if it receives an ignition signal before
it receives an alarm disarm signal.
Another feed to the ignition switch is provided by the BCU to provide switch illumination.
A key-in warning can be enabled or disabled. When the key-in warning is enabled, an audible warning is generated
if the ignition key is in and the driver's door is opened.
Passive coil
The passive coil is located around the ignition key barrel. When the BCU detects that the ignition key has been turned
to the crank position, the vehicle's immobilisation system is activated and a signal is sent to the passive coil at a
frequency of 125 kHz. The magnetic field generated in the coil is induced in the remote transmitter to trigger a re-
mobilisation signal.
BBUS/ alarm sounder/ vehicle horn
The BBUS is an audible warning device which operates under the control of the BCU if the anti-theft system is
activated or the vehicle battery is disconnected. The unit contains its own internal battery power source which is
charged via a feed from the passenger compartment fuse box. The BBUS will not sound if the battery is disconnected
while the security system has not been set.
Some markets utilise an alarm sounder which operates independently or in conjunction with the vehicle horn if the
anti-theft system is triggered.

ALARM SYSTEM AND HORN
DESCRIPTION AND OPERATION 86-4-1
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ALARM SYSTEM AND HORN DESCRIPTION AND OPERAT ION

ALARM SYSTEM AND HORN
86-4-2 DESCRIPTION AND OPERATION
Alarm system component layout
RHD shown, LHD similar