1999 LAND ROVER DISCOVERY Workshop Manual

BODY CONTROL UNIT
86-3-34 DESCRIPTION AND OPERATION
Key-in warning
The BCU can be programmed to one of two options:
lOption 1 – no timeout.
lOption 2 – no key-in warning.
The BCU issues an audible warning No. 2 request, depending on the status of the following inputs:
lIgnition state.
lIgnition key inserted.
lDriver's door open.
If the key-in warning is programmed into the BCU for operation, audible warning No.2 will be requested if the ignition
switch is off, the ignition key inserted signal is on and the driver's door open signal is ON.
In the event of a communications link failure occurring, the audible warning request is not sent to the instrument pack.
SLABS HDC warning
The BCU issues an audible warning No. 3 request, depending on the status of the following inputs:
lIgnition state.
lSLABS HDC warning.
The SLABS warning transmitted by the SLABS ECU is a 2 Hz signal, audible warning No. 3 is requested on every
falling edge of this signal. If the signal from the SLABS ECU stays low for more than 650 ms, audible warning No. 3
is requested every 2 seconds, for 30 seconds, while the signal stays low.
In the event of a communications link failure occurring, the audible warning request is not sent to the instrument pack.
Transfer box in neutral warning
If the transfer box is in the neutral position and the ignition switch is on, the BCU issues an audible warning No. 4
request. The BCU checks for the following inputs:
lTransfer box neutral selected.
lIgnition on.
The transfer box in neutral warning is activated by communicating with the instrument pack via the serial datalink. If
a communications link failure occurs while the transfer box in neutral warning is active, the audible warning will not
operate.
Lights on warning
If the ignition switch is off while the side lamps or headlamps on and the driver's door is opened, the BCU issues an
audible warning No. 5 request.
The BCU checks for the following inputs:
lDriver's door open.
lIgnition on.
lSide lamps.
lDipped beam state.
lMain beam state.
The lights on warning is activated by communicating with the instrument pack via the serial datalink. If a
communications link failure occurs while the lights on warning is active, the audible warning will not operate.
SLABS raise/lower
Before enabling a SLS vehicle raise/ lower request, the BCU checks the logical condition of the following inputs:
lIgnition state.
lSLABS raise request.
lSLABS lower request.
If the ignition switch is in position 0 or I, the vehicle raise/ lower request is off.
With the ignition switch in position II, and the 'SLABS raise' request and 'SLABS lower' request both off, the vehicle
raise/ lower request output is driven at 25 Hz with a 50% duty cycle and the vehicle height remains unchanged.
If the 'SLABS lower' request input is on, the vehicle raise/lower request output is driven at 25 Hz with a 25% duty cycle,
lowering the vehicle.
If the 'SLABS raise' request input is on, the vehicle raise/lower request output is driven at a 25 Hz with a 75% duty
cycle.

BODY CONTROL UNIT
REPAIRS 86-3-35
REPAIRS
Body control unit (BCU)
$% 86.55.75
Remove
1.Release fixings and remove battery cover.
2.Disconnect battery earth lead.
3.Remove 4 bolts securing glove box and remove
glove box. 4.Remove 4 fixings securing closing panel and
remove panel.
5.Disconnect 5 multiplugs from BCU.
6.Remove nut and bolt securing BCU to bracket
and remove BCU.

BODY CONTROL UNIT
86-3-36 REPAIRS
7.Remove rubber ring from locating peg.
Refit
1.Fit rubber ring to new BCU.
2.Fit BCU to bracket and secure with nut and bolt.
3.Connect multiplugs to BCU.
4.Fit closing panel and secure with fixings.
5.Fit glove box and secure with bolts.
6.Connect battery earth lead.
7.Fit battery cover and secure with fixings.
8.Programme and calibrate new BCU using
TestBook.

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

ALARM SYSTEM AND HORN
DESCRIPTION AND OPERATION 86-4-3
1Theft deterrent LED
2Receiver
3Volumetric sensors
4Central door locking switch
5Body Control Unit (BCU)
6Bonnet activated alarm switch
7Vehicle horn
8Alarm sounder
9Fuel cut off switch
10Fuel flap release switch
11Door latch switches, drivers door key lock/
unlock switches
12Battery Backed Up Sounder (BBUS)
13Passive remobilisation exciter coil

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 86-4-5
Description
General
The anti-theft system deters the theft of the vehicle with both active and passive systems. The active systems monitor
the vehicle perimeter and, in some markets the vehicle interior, for intrusion. If the system detects intrusion, an alarm
sounds. The passive systems include a vehicle immobiliser as well as protection against intrusion through super
locking the doors. The vehicle is immobilised whenever the ignition key is removed from the ignition switch. Super
locking prevents the interior door handles from opening the doors. In addition, there are many features and functions
that enhance system operation.
It is possible to perform the various functions associated with the anti-theft system remotely. To accomplish this, the
handset generates a radio frequency when the lock button or unlock button is depressed. This signal is transmitted
to the Body Control Unit (BCU) via a receiver located in front of rear sunroof beneath the headlining. Precise alignment
of the handset to the receiver is not necessary. The approximate operating range between the handset and the
receiver is 10 metres (33 feet).
It is important to understand the configuration of the system on each particular vehicle. There are many
different combinations of features with dedicated operating modes. System configuration for each vehicle
can be determined using TestBook.
The anti-theft system is controlled centrally by the BCU, which is located below and behind the passenger glovebox.
A serial communication link communicates between the Intelligent Driver Module (IDM) located within the fusebox,
the BCU and the LED located in the instrument panel.
The state of the alarm is stored in the BCU. If the battery is disconnected while the alarm is armed, the alarm will be
triggered when the battery is reconnected.
NOTE: Disconnecting the battery while the alarm is armed triggers the alarm. Always disarm the alarm system before
disconnecting the battery.
The BCU also receives inputs from the following components:
lIgnition key in sensor.
lIgnition switch.
lFuel cut off switch.
lFuel flap release switch.
The BCU also interacts with the following components:
lStarter relay.
lVehicle horns.
lDirection indicators.
lFuel flap release actuator.
lCourtesy lamps.