Discovery 2. Manual - part 738

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:

All doors and hinged panels are in the closed position.

Ignition key out of the ignition switch.

Inertia 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.

BODY CONTROL UNIT

86-3-20 DESCRIPTION AND OPERATION

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%.

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.

BODY CONTROL UNIT

DESCRIPTION AND OPERATION 86-3-21

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.

Security system status LED
The LED flashes when the anti-theft system has been set. There are four different flash rates dependent on mode of
operation or other system information.

Central door locking
The doors can be locked by the following methods:

Pressing the lock button on the remote transmitter.

Locking the vehicle from the driver's door with the key.

Pressing the lower half of the central door lock switch.

Pushing the sill button down (will only lock that particular door).

By driving over 7 km/h (4 mph) – ( if the speed related locking function has been enabled).

The BCU will prevent locking if the logical conditions for locking are not satisfied. Conditions which will prevent door
locking include:

Driver's door open.

Ignition switch on.

Inertia switch tripped.

Vehicle is already superlocked.

A mislock may occur if the logical conditions are not met.

The doors can be unlocked by the following methods:

Pressing the unlock button on the remote transmitter

Unlocking the vehicle from the driver's door with the key.

Pressing the upper half of the central door locking switch (not operational if the vehicle is superlocked).

Pulling the interior door handles (not operational if the vehicle is superlocked).

Inertia switch being triggered while the ignition is on and the security system is de-activated.

The BCU supplies information via the serial data bus to the IDM to energise the coil of the relays for each of the door
lock actuators.

The BCU normally checks the following inputs to determine lock/ unlock requirements:

Unlock request.

Lock request.

Superlock request.

Single point entry request.

Lock passenger and rear doors request.

BODY CONTROL UNIT

86-3-22 DESCRIPTION AND OPERATION

The following outputs are generated by the BCU dependent on the prevailing logic conditions and the input requests
the BCU has detected:

Unlock all doors enable.

Lock passenger and rear doors enable.

Superlock all doors enable.

Lock driver's door enable.

All lock/ unlock pulses have a duration of 800 ms.

Input/Output logic for door lock/unlock

To determine if the vehicle speed is appropriate for enabling speed related locking, the BCU uses the vehicle speed
signal supplied over the serial data bus from the instrument pack.

Electric windows and sunroof
Three modes of operation are available:

Driver cancel – the front windows, rear windows and sunroof will be disabled 44 seconds after the driver's door
is opened.

All cancel – The front windows, rear windows and sunroof will be disabled 44 seconds after any door is opened.

No cancel – the front windows, rear windows and sunroof will be disabled when the ignition is turned off.

The BCU will allow window and sunroof operation when the ignition key is in position II. The BCU provides a voltage
to the window control switches. When the switches are pressed, they provide a path to earth to complete the circuit
and initiate window operation. Window and sunroof operation is suspended when the ignition switch is in the crank
position.

For front window operation, the BCU checks the status of the following inputs:

Ignition state.

Driver's door open.

Passenger or rear door open.

Front right window down.

Front right window up.

Front left window down.

Front left window up.

Right window stall detect.

Left window stall detect.

The front window motors are directly connected to the BCU by two wires. Each wire can be used as a feed or return,
dependent on the required direction for motor operation (open or close). The BCU provides the following outputs:

Right window up.

Right window down.

Left window up.

Left window down.

The electric front windows are enabled when the ignition switch is in position II and is disabled if the ignition switch is
moved to the crank position.

Output/Request

Superlock all
doors enable

Unlock all doors

enable

Lock driver's

door enable

Lock passenger

and rear doors

enable

Unlock request

Lock request

Superlock request

Single point entry request

Lock passenger and rear doors
request

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