Discovery electrical Manual - part 74

THEFT ALARM SYSTEM (EXCEPT NAS)

T1

CIRCUIT OPERATION

2

Perimetric Protection

The system is perimetrically armed whenever the
vehicle is manually central door locked using the
driver’s door key. A lock request from the handset
will volumetrically arm the theft alarm.

Volumetric Protection

Using the handset transmitter will turn on and off
volumetric protection. In volumetric mode all doors,
tailgate, and bonnet are protected against
unauthorised entry, and the Ignition Switch is
protected from being switched on. In addition, the
vehicle interior is protected using the Alarm Sensor
(X213).

Theft Alarm Disarming

(Perimetric and Volumetric Modes)

The theft alarm can only be disarmed with the
handset (or EKA code).

NOTE: The theft alarm system cannot be disarmed
using the driver’s door key.

Partially Armed Mode

The System will enter the “partially armed” mode
whenever one of the following conditions is valid
during theft alarm arming:

movement takes place inside the vehicle within
15 seconds of the lock signal being received

a door, tailgate, or bonnet is open.

The engine will be immobilised and cranking is
inhibited. The alarm will sound if ignition is turned to
start position. The alarm will protect the following:

If any of the doors caused partial arming, then
opening the tailgate or bonnet will sound the
alarm.

If the tailgate caused partial arming, then the
opening of any doors or the bonnet will sound
the alarm.

If the bonnet caused partial arming, then the
opening of any doors or tailgate will sound the
alarm. Volumetric protection is also armed.

If two of the above cause partial arming, then the
third is still protected.

If the doors, tailgate or bonnet is subsequently
closed, after a 5 second delay, the system will fully
arm.

Engine Cranking

It is only possible to crank the engine when ignition
is ON and alarm disabled.

Alarm Sounder

When an intrusion is detected, the Alarm Sounder
(Z171) will sound and the hazard lamps flash (where
territorial regulations allow) for 30 seconds. The
alarm must be retriggered before the Alarm Sounder
will sound again.

Two different types of Alarm Sounders are available:

1. Normal Alarm Klaxon (Alarm Sounder (Z171))

2. Battery Backed Up Alarm Sounder (Z272)

The Battery Backed Up Alarm Sounder (Z272) is an
alarm sounder which contains its own internal
battery. When the Ignition is on, the internal battery
is charged via an Ignition feed. If either the
connector is removed or the wires to it are cut, then
the sounder will sound for 3 minutes.

To disconnect the Battery Backed Up Alarm Sounder
(Z272):

Turn Ignition On (Pos. II)

Turn Ignition Off

Disconnect within 15 seconds

To silence if triggered:

Connect

Disarm Alarm

Turn Ignition On (Pos. II)

THEFT ALARM SYSTEM (EXCEPT NAS)

T1

CIRCUIT OPERATION

3

Inertia Switch

An inertia switch is incorporated in the Theft Alarm
Unit (Z163). If ignition is on and the vehicle receives
an impact sufficient to activate the inertia switch, the
unit will signal to unlock central locking actuators and
flash hazard lights. Central locking will remain
disabled for a period of 0 to 5 minutes. To reset, turn
ignition off and then on after the time period has
elapsed.

Alarm Sensor (X213)

The sensor operates by emitting an air pressure
carrier wave and receiving the wave back. Any
disturbace within the vehicle which disturbs the wave
will be detected, triggering the alarm. When the
volumetric sensor is activated, it monitors movement
within the vehicle for 15 seconds before detecting
and responding to intrusions. If the sensor detects
movement within the vehicle, it delays arming until a
15 seconds quiet period has elapsed. If continuous
movement is detected, the alarm will not arm
volumetrically.

ENGINE IMMOBILISATION FUNCTION

(Not on all vehicles!)

The engine will be immobilised whenever the theft
alarm is armed or the the Theft Alarm Unit (Z163)
enters the Passive Immobilisation mode (regardless
of whether or not the alarm is armed). There are two
methods of Engine Immobilisation featured:

1. Electronic Engine Immobilisation (used on

MFI–T16 and 300 Tdi with EDC engines)

2. Remote “Smart Spider” Immobilisation (used on

MFI–V8 and 300 Tdi without EDC engines)

The vehicle may only be mobilised by using the
handset or entering the correct EKA code.

Electronic Engine Immobilisation

(MFI–T16) (300 Tdi with EDC)

The electronic engine immobilisation is controlled
jointly by the engine management system’s
Electronic Control Module (ECM) (Z132) and the
Theft Alarm Unit (Z163).

When the Theft Alarm Unit (Z163) immobilises the
vehicle, it sends a signal to the ECM. The ECM then
immobilises the engine management system until a
mobilise signal is received from the Theft Alarm Unit
(Z163).

Remote “Smart Spider” Immobilisation

(MFI–V8) (300 Tdi without EGR)

The Remote “Smart Spider” Immobilisation is
controlled jointly by the Engine Immobilisation
Control Unit (Spider) (Z271) and the Theft Alarm
Unit (Z163). When the Theft Alarm Unit (Z163)
immobilises the vehicle, it sends a signal to the
Engine Immobilisation Control Unit (Spider) (Z271).
The “Spider” then interrupts the starter circuit, fuel
pump circuit, and Ignition coil circuit for MFI–V8
engines, or the starter circuit and the fuel pump
shutoff solenoid circuit for 300 Tdi without EGR
engines. These circuits will remain interrupted until
the “Spider” receives a mobilise signal from the Theft
Alarm Unit (Z163).

Diesel Fuel Shut–off Immobilisation (DDS) 
(300 Tdi with EGR)

Diesel Fuel Shut–off Immobilisation is controlled
jointly by the Diesel Immobilisation Unit (DDS)
(Z276) and the Theft Alarm Unit (Z163). When the
Theft Alarm Unit (Z163) immobilises the vehicle, it
sends a signal to the Diesel Immobilisation Unit
(DDS) (Z276). The Diesel Immobilisation Unit (DDS)
(Z276) then interrupts it’s internal fuel shut–off
solenoid circuit. This circuit will remain interrupted
until the Diesel Immobilisation Unit (DDS) (Z276)
receives a mobilise signal from the Theft Alarm Unit
(Z163).

THEFT ALARM SYSTEM (EXCEPT NAS)

T1

CIRCUIT OPERATION

4

Passive Immobilisation

The following conditions will passively immobilise the
vehicle:

30 seconds after ignition has been turned off and
the driver’s door has been opened

5 minutes after ignition has been turned off

5 minutes after disarming the theft alarm

The vehicle can be mobilised by any of the following
methods:

Turn the ignition on (The handset must be
functioning properly and within close proximity to
the key!)

Press unlock button on the handset (4 times if
out of synch)

Press lock button on the handset with Ignition
Switch (X134) in position II (4 times if out of
synch)

Enter EKA code

NOTE: The vehicle will remain immobilised by
attempting to turn the ignition on with the handset
detached from the key ring (or with an improperly
functioning handset)

Passive Immobilisation Coil (Z270)

A magnetic field is generated by the passive
Immobilisation Coil (Z270) contained in the steering
column. This field excites a receiving coil in the
handset causing it to transmit a mobilisation signal to
the Theft Alarm Unit (Z163). If the Theft Alarm Unit
(Z163) does not receive this signal from the handset,
the vehicle will remain immobilised.

Vehicle Status Indication

Vehicle status is indicated by up to four devices:

1. Hazard lamps

2. Theft Alarm LED (Contained in the Instrument

Cluster (Z142))

3. Engine Immobilised Warning Lamp (EIWL)

(Contained in the Instrument Cluster (Z142))

4. Alarm Sounder

Hazard Lamps

When the vehicle arms in either mode, the hazard
lamps will flash up to three times when the alarm is
armed and one time when disarmed.

Theft Alarm LED

Slow Flash: Immobilised or immobilised and
armed

Rapid Flash: Volumetrically armed

Intermittent Rapid Flash: Perimetrically armed

No Flash for 10 Seconds: Mislock

Continuous: Driver’s door open (or ignition on)
and immobilised

NOTE: The Theft Alarm LED may also be used to
indicate other conditions.

Engine Immobilised Warning Lamp (EIWL) (Not on
all vehicles!)

Flashing: Immobilised

Continuous: Immobilised (Cirrus Fail), or an
attempt has been made to start the vehicle
without the handset attached to the key ring (or
handset battery needs to be replaced).

THEFT ALARM SYSTEM (EXCEPT NAS)

T1

CIRCUIT OPERATION

5

Handset Transmitter Resynchronisation

The Theft Alarm Unit (Z163) will remain
synchronised with the handset unless:

The handset’s batteries have been removed

The vehicle’s battery has been disconnected

NOTE: All handsets must be resynchronised when
the vehicle’s battery has been disconnected.

To resynchronise a handset the vehicle must be in
an unlocked and disarmed state. Resynchronisation
consists of 4 presses of either the lock or unlock
button.

Handset Low Battery Warning

When the handset batteries are low, the Theft Alarm
Unit (Z163) will enter the “low battery mode”. The
Theft Alarm LED will flash to indicate “low battery
mode”, and the hazard lamps will not flash when the
alarm is disarmed.

Interior Lamps

The Theft Alarm Unit may be configured to perform
full interior Lamp delay and soft–fade functionalities.

Power Up Mode

The alarm system always remembers the state it
was left in when power was removed. If the alarm
powers up in an alarmed state, it will enter a special
“power up mode”.

Emergency Key Access (EKA)

EKA is used to disarm the theft alarm and mobilise
the vehicle in the event of a handset failure. This is
possible through a series of locks and unlocks with
the key in the driver’s door lock cylinder. With the
vehicle locked and the alarm armed, turn the key the
required number of times according to the following
sequence:

1. To enter the first digit, turn the key the required

number of times to the unlock position.

2. To enter the second digit, turn the key the

required number of times to the lock position.

3. To enter the third digit, turn the key the required

number of times to the unlock position.

4. To enter the fourth digit, turn the key the required

number of times to the lock position.

5. Turn the key to the unlock position to unlock the

doors, disarm the alarm, and mobilise the
vehicle.

NOTE: The key must be fully turned to the rest and
lock/unlock position each time.

If the wrong EKA code has been entered, an audible
warning will be heard. After 3 wrong attempts, you
must wait 30 minutes. To clear a partially entered
code, simply hold the key in the lock position for at
least 5 seconds.