Discovery 2. Manual - part 320

 

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Discovery 2. Manual - part 320

 

 

BODY CONTROL UNIT

DESCRIPTION AND OPERATION 86-3-21

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:

l

Pressing the lock button on the remote transmitter.

l

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

l

Pressing the lower half of the central door lock switch.

l

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

l

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:

l

Driver's door open.

l

Ignition switch on.

l

Inertia switch tripped.

l

Vehicle is already superlocked.

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

The doors can be unlocked by the following methods:

l

Pressing the unlock button on the remote transmitter

l

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

l

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

l

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

l

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:

l

Unlock request.

l

Lock request.

l

Superlock request.

l

Single point entry request.

l

Lock passenger and rear doors request.

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

l

Unlock all doors enable.

l

Lock passenger and rear doors enable.

l

Superlock all doors enable.

l

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.

Output/Request

Superlock all 
doors enable

Unlock all doors 

enable

Lock driver's 

door enable

Lock passenger 

and rear doors 

enable

Unlock request

0

1

0

0

Lock request

0

0

1

1

Superlock request

1

0

1

1

Single point entry request

0

1

0

1

Lock passenger and rear doors request

0

0

0

1

BODY CONTROL UNIT

86-3-22 DESCRIPTION AND OPERATION

Electric windows and sunroof
Three modes of operation are available:

l

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

l

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

l

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:

l

Ignition state.

l

Driver's door open.

l

Passenger or rear door open.

l

Front right window down.

l

Front right window up.

l

Front left window down.

l

Front left window up.

l

Right window stall detect.

l

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:

l

Right window up.

l

Right window down.

l

Left window up.

l

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.

The BCU checks the status of the following inputs to determine when to provide the rear window enable and sunroof 
enable output signals:

l

Ignition state.

l

Driver's door open.

l

Passenger or rear door open.

The rear window enable and sunroof enable lines are on when the ignition switch is in position II, and are switched 
off if the ignition switch is moved to the crank position.

The BCU monitors the circuit current draw when the windows are operating to detect the occurrence of a stall 
condition. If the BCU determines that the window has stalled, it will cut the power supply to stop the operation of the 
window motor. The BCU only starts to check for a stall condition after the window has been operating for 500 ms. This 
delay period enables the initial current surge to pass and eliminates false detections of window stall. A stall condition 
is activated when a nominal current value is exceeded for a period greater than 300 ms.

If the BCU detects that it has been operating the same window motor in one direction for more than 10 

±

 0.2 seconds, 

without the BCU detecting a stall condition or the control switch being released, it will automatically stop operation of 
the window motor (timed out). Window operation can resume when the window switch is released and pressed again. 
If the window was operating in one touch mode, the window operation will resume on the next press of the window 
switch.

One touch mode automatically lowers the window to its fully open position, without the need for the window switch to 
be kept pressed for the duration of the window travel. One touch mode is initialised if the window switch is pressed 
for a period of less than 0.4 

±

 0.2 second. One touch mode continues to lower the window until the BCU detects:

l

A stall condition exists (window has reached bottom of travel).

l

Window switch is repressed in either direction for more than 0.4 

±

 0.2 second.

l

The BCU has operated the motor for a period greater than 10 

±

 0.2 seconds.

BODY CONTROL UNIT

DESCRIPTION AND OPERATION 86-3-23

A timeout function is included which allows the windows and sunroofs to be operated for a period of 44 

±

 1 seconds 

after the ignition key has been removed from the ignition switch. The timeout function will be cancelled if the BCU 
detects the following conditions:

l

The driver's door has been closed after the ignition has been switched off.

l

Any door open after the ignition is switched off.

The preconditions are programmed into the BCU dependent on market specification.

The BCU does not directly control rear window operation, but it can request the IDM to remove the power feed to the 
rear windows. The IDM enables power supply to be provided to the rear lift relay in the passenger fuse box. When the 
relay coil is energised the relay contacts close and power is applied to the rear window motor. If the window lift 
isolation switch located in the centre console is latched out, the earth path from the LH and RH rear door window 
switches is broken and operation of the rear window motors through the use of the rear window switches is prevented. 
Rear window operation using the console switches is not affected by the isolation switch.

In the event of a communications link failure occurring while rear window enable is on, the relay remains on until the 
ignition switch is turned to the off position.

Heated screens
The heated screen time-outs and logical operations are controlled by the BCU.

Heated front screen
The BCU provides an output to the heated front screen relay and a 'heated front screen active signal' for the heated 
front screen warning lamp. The BCU uses the status of the following inputs to determine the appropriate logical 
operations for this feature:

l

Ignition state.

l

Engine running (link from instrument pack).

l

Heated front screen selected (non-latched button pressed).

If the ignition switch is not in position II, or the engine running signal is OFF, the heated front screen will not be active.

The heated front screen operation period and voltage supply is controlled by the BCU. The BCU receives a voltage 
supply feed from the engine compartment fuse box and an ignition switched supply through a fuse in the passenger 
compartment fuse box. When the heated front screen switch is operated, it completes a path to earth, signalling a 
request for heated screen operation to the BCU. The BCU then supplies a feed to the heated front screen switch to 
light the switch indicator, and earths the supply from the coil of the heated screen relay to turn the heated front screen 
on. The BCU maintains a supply for a predetermined time (5 minutes), then opens the earth path after the time out 
period to turn the heated screen off. During the timeout period, if the heated front screen switch is pressed a second 
time, the circuit is also interrupted to turn off the supply to the heated front screen.

On vehicles fitted with air conditioning, the heated front screen is also operated by the ATC ECU when DEF (defrost) 
is selected. In this case the ATC ECU provides the trigger signal to the BCU to turn the heated front screen circuit on 
or, if it is already on, to re-start the time out period.
 

 + 

 AIR CONDITIONING, DESCRIPTION AND OPERATION, Description.

In the event of a communications link failure occurring while the heated front screen relay is on, the relay and lamp 
will remain on until the ignition switch is turned off or the time-out period elapses or the heated front screen switch is 
pressed.

Heated rear window
The heated rear window will only function when the engine is running, and is operated by a non-latching switch on the 
instrument pack cowl.

The BCU provides a 'heated rear window enable output' and a 'heated rear window active warning lamp signal' based 
on the logic status of the following inputs:

l

Ignition state.

l

Engine running (link from instrument pack).

l

Heated rear window selected (non-latched button pressed).

If the ignition switch is not in position II, or the engine running signal is OFF, the heated rear window will not be active.

BODY CONTROL UNIT

86-3-24 DESCRIPTION AND OPERATION

The heated rear window operation period and voltage supply is controlled by the BCU. The BCU receives a voltage 
supply feed from the engine compartment fuse box and an ignition switched supply through a fuse in the passenger 
compartment fuse box. When the heated rear window switch is operated, it completes a path to earth, signalling a 
request for heated rear window operation to the BCU. The BCU then supplies a feed to the heated rear window switch 
to light the switch indicator, and earths the supply from the coil of the heated rear window relay via the IDM to turn the 
heated rear window elements on. The BCU maintains a supply for a predetermined time (15 minutes), then opens the 
earth path after the time-out period to turn the heated rear window operation off. If the heated rear window switch is 
pressed a second time, the circuit is also interrupted to turn off the supply to the heated front screen.

On vehicles fitted with air conditioning, the heated rear window is also operated by the ATC ECU when DEF (defrost) 
is selected. In this case the ATC ECU provides the trigger signal to the BCU to turn the heated rear window circuit on 
or, if it is already on, to re-start the time out period
 

 + 

 AIR CONDITIONING, DESCRIPTION AND OPERATION, Description.

In the event of a communications link failure occurring while the heated rear window enable is on, the relay and lamp 
will be de-activated.

Wipers and washers
Front and rear wash/ wipe operations are controlled by the BCU via the IDM.

Front wipers and washers
When front intermittent wipe is selected using the wiper switch on the column stalk, the BCU signals the IDM to 
operate the wiper motor. The IDM then supplies a voltage to the normal speed winding of the wiper motor for a period 
of no longer than 500 ms. The timed feed ensures the wiper motor operates, but does not complete more than a single 
wipe of the screen. The BCU checks the position of the delay switch to determine the delay period which should be 
utilised for the intermittent wipe operation. The delay period of the front intermittent wipe is maintained until the wiper 
switch is moved to the off, normal or fast speed position, or the delay period is changed.

When front intermittent wipe is selected, a delay period of 500 ms will be incurred before the wipers operate. This 
delay prevents the occurrence of a wipe action when the wiper switch is changed to the off position from the normal 
or fast modes of operation.

To enable the front intermittent wipe facility, the BCU checks the state of the following inputs:

l

Ignition state.

l

Front intermittent wiper switch.

l

Front intermittent wiper rate.

If the ignition switch is in the off or crank position, the front wipers are not active and the front wiper enable output is 
switched off.

If the option to initiate a wipe action in addition to a front screen wash action has been configured in the BCU, the 
wipers will operate 400 ms after the washer pump becomes active. If the washer switch is released within 400 ms, 
the wipers will not be activated. If a washer switch is pressed for longer than 400 ms, the BCU will operate the wipers 
after an initial delay of 400 ms, and will continue to operate for as long as the washer switch is depressed plus an 
additional 4 seconds.

The front wash/ wipe programme can be configured to operate in one of two ways:

l

Option 1 – normal.

l

Option 2 – no wipe.

The BCU checks for the following inputs:

l

Ignition state.

l

Front washer pump switch.

The BCU can provide the following wash / wipe outputs depending on the logic states prevailing:

l

Front wiper enable.

l

Front wash/ wipe in progress flag.

In the event of a communications link failure occurring while the front wash/ wipe programme is in operation, the front 
wiper enable output is switched off.

 

 

 

 

 

 

 

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