Body Control Unit Land Rover Discovery L318

General

The Body Control Unit (BCU) is located behind the passenger glovebox and is connected to the main harness by four connectors on its bottom edge and an additional connector located on the side of the BCU casing. Mounting the BCU behind the fascia makes it reasonably inaccessible for intruders to disable the anti-theft system.

The BCU uses solid-state microprocessor control to perform logical operations and timing functions for a variety of the vehicle's electrically operated systems, these include

1. Door locking.
2. Anti-theft alarm and immobilization system.
3. Exterior lighting including direction indicators and hazard warning lamps.
4. Courtesy lighting.
5. Wipers and washers.
6. Electric windows and sunroof.
7. Heated windows.

The BCU also communicates with several other electronically controlled systems such as the EAT ECU and SLABS ECU and also has a datalink between the Intelligent Driver Module (IDM) and the instrument pack. The datalink is a low speed bus capable of transmitting and receiving messages at a data rate of 10,400 bits per second. Additional inputs and outputs to peripheral devices are included which are necessary for determining vehicle status for particular logical operations e.g. crank, ignition key inserted, fuel flap enable etc.

The BCU receives its power supply from the engine compartment fuse box, and is protected by a 10 A fuse.

The BCU communicates with the IDM to provide the control signals to perform power switching operations in conjunction with dedicated relays.

IDM

The IDM is integrated into the passenger compartment fuse box, which is mounted behind the fascia below the steering column. There are no harnesses between the fuse box and the IDM. The IDM performs the power switching operations for several of the vehicle's electrical systems.

The IDM communicates with the BCU and the instrument pack via a serial interface. If the BCU or the IDM is replaced, the communications link between the two units has to be re-established. This can be done either by switching on the ignition and leaving it on for five minutes, or by using TestBook. The vehicle immobilization will remain active until the communications link between the BCU and IDM has been re-established.

Transit mode

To prevent excessive battery drain during transit to overseas markets, the vehicle is placed in a transit mode. The following functions are disabled when the vehicle is in transit mode

1. Volumetric sensors.
2. Passive immobilization.
3. Immobilization of the vehicle by use of door lock.
4. Ignition key interlock.
5. Electric seat enable time-out with driver's door open.

Power supply

Battery supply to the BCU and the IDM is provided through a 10 A fuse located in the engine compartment fuse box.

The BCU unit receives an ignition switched power supply (ignition switch position II) input via a 10 A fuse in the passenger compartment fuse box.

The BCU receives a signal when the ignition switch is turned to the crank position, it then supplies an earth path to the starter relay coil, to enable the crank operation by supplying power through the starter relay contacts to the starter motor.

Battery voltage is monitored and BCU operation will function normally between 8 and 18 volts. Between 5.7 and 8 volts the BCU is in the 'under volts' state. The status of the battery is used to determine which outputs may be driven.

If a voltage supply above 18 volts is experienced, outputs will not normally be driven except for those functions which are required during cranking (robust immobilization, antenna coil, crank enable relay and feed to gear position switch contacts W, X, Y, Z). In the over voltage state the vehicle can be driven, but all other functions are disabled and outputs are switched off (power windows, heated screen, direction indicators etc.).

All functions are disabled on power up until communications between the BCU and IDM have been established. If communications cannot be established, operation will commence with degraded functionality.

Battery supply to the IDM is provided through the inertia switch and a 10 A fuse in the engine compartment fuse box. If the inertia switch contacts are closed battery voltage is available at the IDM; if the inertia switch contacts are open there is no battery supply to the IDM. The supply condition of the IDM is signalled to the BCU via the serial bus. If the inertia switch is operated (contacts open) the change in state is detected by the BCU which unlocks the doors if the ignition switch is in position II and the alarm is not set.

The BCU is earthed through a hard-wire connection.

Inputs and outputs

The BCU and IDM process inputs and provide the necessary outputs for control and operation of the vehicle's 'body' systems.

BCU inputs

The BCU processes signals received from the following components

1. Door latch switches.
2. Driver's door key lock/ unlock switches.
3. Bonnet activated security system.
4. Volumetric sensors.
5. Central Door Locking (CDL) switches.
6. Remote transmitter (via receiver unit).
7. Inertia fuel cut-off switch.
8. Ignition switch.
9. Fuel flap release switch.

The input voltages (VIN) for BCU digital signals are defined as follows

1. Logic 1 when VIN >= 6V.
2. Logic 0 when VIN <= 2V.

BCU input voltages between 2 and 6 volts are indeterminate and cannot be guaranteed.

Analogue input voltages are measured as a ratio with respect to battery voltage.

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

1. Interior courtesy lamps.
2. Fuel flap release actuator.
3. Anti-theft status LED.
4. Engine Control Module.
5. Door lock actuators.
6. Direction indicators and hazard warning lamps.
7. Headlamps.
8. Alarm sounder.
9. Vehicle horns.
10. Battery backed sounder.
11. Starter relay.
12. Passive re-mobilization 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.

Scheme 1

The pinout details for the BCU connectors are defined below

Scheme 2

PIN DESCRIPTION

Scheme 3

PIN DESCRIPTION

Scheme 4

PIN DESCRIPTION

Scheme 5

PIN DESCRIPTION

Scheme 6

IDM inputs

The IDM inputs are communicated to the BCU using the serial datalink so that the BCU can perform the necessary logic operations

The VIN for IDM digital signals are defined as follows

1. Logic 1 when VIN >= 8V.
2. Logic 0 when VIN <= 2V.

IDM input voltages between 2 and 8 volts are indeterminate and cannot be guaranteed.

SIGNAL DESCRIPTION

IDM outputs

The IDM receives the following signals from the BCU using the serial datalink to provide power outputs

SIGNAL DESCRIPTION

Scheme 7

RHD illustrated

The BCU has a serial connection to the diagnostic socket to allow unit interrogation using TestBook.

In addition to fault diagnosis, the BCU can be programmed with the following information

1. Plip codes.
2. Options.
3. VIN code.
4. EKA code.
5. EEPROM locking.

The following manufacturing details are programmed into the BCU which can be accessed using TestBook

1. Date of manufacture.
2. Hardware version number.
3. Unit serial number.
4. Odometer reading.

It is not possible to use the diagnostic bus to communicate with the BCU via TestBook when the security system is active (except for passive immobilization). This is a security measure to ensure that no key programming or market configuration can take place if the operator is not in possession of a valid remote transmitter or the vehicle keys.

The BCU is normally programmed to accept two remote transmitters, but a further two remote handsets can be programmed into the BCU and one optional Self Levelling Suspension (SLS) transmitter. All remote transmitters need to be available if TestBook is to be used to re-configure the BCU.

Programmable options

The BCU can be programmed with a number of options to satisfy specific market requirements and customer preferences. The options can be set using TestBook.

PROGRAMMABLE OPTIONS

Anti-theft system

The BCU controls the logical switching operations for enabling and activating the anti-theft system. Features include

1. Perimetric protection - monitors the condition of doors and hinged panels.
2. Volumetric protection - monitors the vehicle's interior space.
3. Remote locking, superlocking and unlocking functions.
4. Engine immobilization and re-mobilization.
5. Advanced mislock detection and automatic compensation.
6. EKA code functions.
7. Customer configuration options.
8. Market configuration options.

Immobilization

The immobilization system comprises the following components

1. RF receiver.
2. RF transmitter/ transponder.
3. Transponder coil.
4. BCU.
5. Door switches, door lock switches and bonnet switch.
6. IDM.
7. ECM.
8. Starter solenoid relay.
9. Status LED.

Alarm system

The alarm system comprises the following components

1. RF receiver.
2. RF transmitter.
3. BCU.
4. IDM.
5. Door switches, door lock switches and bonnet switch.
6. Battery backed-up sounder (BBUS).
7. Status 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.

Central Door Locking (CDL)

The BCU carries out the logic control operation for CDL. A CDL switch is mounted on the fascia panel and has two inputs to the BCU, one for lock and one for unlock.

Door locking and unlocking can be performed using the remote transmitter in the keys and the receiver unit located above the vehicle's headlining, behind the rear sunroof aperture. The receiver detects the signals sent from the remote transmitter and sends a decoded signal to the BCU for processing.

Four methods of door locking are available

1. Remote handset locking.
2. Vehicle key locking.
3. CDL switch locking.
4. Speed related locking.

Two security levels of door locking are available, CDL and Superlocking. The anti-theft alarm system works in conjunction with the CDL system.

Electric windows and sunroof

The BCU controls the logical operations and the timing periods for the electric front windows. The rear windows are hard-wired and the two electric sunroofs are controlled by a dedicated ECU which is enabled by the BCU.

The front windows are electrically operated using two rocker switches located in the center console. Electric motors are located in each of the front doors.

The rear windows are enabled by the IDM controlling the operation of the rear window relay located in the passenger compartment fuse box.

Wipers and washers

The wiper and washer functions are controlled by the BCU and the IDM.

The front wipers and washers are operated from the switch stalk located on the right hand side of the steering column and only operate when the ignition switch is in position I or II. The front wipers are operated by a motor located below the windscreen plenum.

The BCU controls the wiper motor frequency of operation via the IDM when intermittent wipe or wash is selected. The front intermittent wipe option features five different intermittent delay periods. The shortest delay period is 3 seconds and this is increased by 2 second increments up to a maximum delay of 11 seconds. The desired delay period for the front wipers is set by the position of the rotary switch located on the wiper column stalk.

The rear wiper switch is located on the instrument pack cowl and is latched when pressed. The rear wiper electric motor is located in the tail door. The rear wiper operation is controlled according to a programmed strategy via the BCU and the IDM. The BCU also checks for a signal from either the reverse lamp switch located in the vehicle gearbox (manual gearbox models) or the gear position switch (automatic gearbox models) for operating the rear wipers when the vehicle is in reverse. The rear wiper and washer only operate when the ignition switch is in position II.

The front and rear washer pumps and the headlamp powerwash (where fitted) are also controlled through the BCU. The washers are operated from electric pumps attached to the washer reservoir located in the left hand wheel arch. The front wash switch is located on the wiper column stalk and is pulled towards the steering wheel to select the washer function. When the front washers are operated, the wipers are also activated for three full cycles. The rear wash switch is located on the instrument pack cowl. The BCU program can be configured in one of two modes of operation

1. No wiper operation when the wash switch is pressed.
2. Wiper action after an initial delay of 400 ms.

Headlamp wash is activated by the BCU via the IDM and operates when the headlamps are on and the front washers function is selected.

Electric seats

The BCU controls the logical operation of the electrically operated front seats. Two modes of operation are available

1. Electric seat adjustment is enabled if the ignition is on or the driver's door is opened for a short time period.
2. Electric seat adjustment is enabled if the ignition is on and the driver's door is closed.

The seats are operated by four electric motors which control the seat cushion rear up/ down, the seat cushion front up/down, seat cushion forward/ rearward and seat squab recline. The electrically powered lumbar adjustment in each seat is operated by a single motorized air pump and a solenoid located on the seat squab frame. The air pump inflates a cushion in the seat squab and the solenoid operates a valve to deflate the cushion. The seat squab and cushion may also contain heater elements to provide heated seat operation.

The switches for electrically operated seats are located either side of the center console.

Direction indicators and hazard warning lamps

The direction indicator lamps are operated from a three position direction indicator switch on the left hand, steering column stalk. The BCU only allows the lamps to work as direction indicators when the ignition switch is in position II. The BCU also controls the lamps to operate as hazard warning lamps and as a visual warning for the anti-theft system, in which cases all lamps flash simultaneously irrespective of the ignition switch position.

System control of the direction indicators and hazard warning lamps is provided by the BCU operating with the IDM and two electronic relays located in the passenger compartment fuse box. The IDM and relays are integral parts of the passenger compartment fuse box and cannot be serviced individually. The serial data bus is used for communication of status and operation requests between the BCU, IDM and instrument pack.

The hazard warning lamps are operated from a latching pushbutton switch located on the fascia.

All direction indicator/ hazard warning lamp bulbs are rated at 5 Watts.

Headlamps

The BCU contains a feature which allow the vehicle headlamps to be turned on when the remote transmitter is pressed (courtesy headlamps).

For markets with daylight running lamps, the BCU controls the logical operation of the daylight running lamps. Options are daylight running lamps are on if the main beam headlamps are off, or the daylight running lamps are on with main and dipped beam off and the gearbox not in Park.

Front fog lamps

For markets with front fog lamps fitted, the BCU controls the operation of the front fog lamps. Options can be selected so that the fog lamps will operate with or without the headlamps on main beam.

Instrument pack

The BCU communicates with the instrument pack via a serial data bus.

1. The instrument pack provides the BCU and IDM with details of vehicle speed.
2. Signals are provided from the IDM to the instrument pack and BCU when the direction indicator lamps are active.
3. For certain markets, the BCU provides a signal to the instrument pack for indicating when the transfer box is in neutral.
4. The IDM can signal the instrument pack to illuminate a trailer warning lamp. This operates when the IDM senses that the current drawn by the indicator circuit exceeds a preset threshold.
5. The odometer reading displayed on the instrument pack LCD screen is also stored in non volatile memory in the BCU. Whenever the ignition is turned from position I to position II, the instrument pack and the BCU compare their stored values.
6. The gear selector position is displayed on the instrument pack LCD screen under the direction of the BCU.

Starting

The starting system comprises a starter motor and solenoid located at the rear right hand side of the engine. A starter relay controlled by the BCU is used to supply battery power for starter solenoid operation. The starter motor receives its feed directly from the battery.

Cruise control

The BCU processes several signals used for cruise control

1. When the brake pedal is pressed, a low voltage brake lamp signal is sent via the BCU to the cruise control ECU.
2. The gear position switch sends an input via the BCU to the cruise control ECU if the selector lever is in Park, Neutral or Reverse.
3. A voltage supply is fed from the BCU to the cruise control SET+ switch.
4. A voltage supply is fed from the BCU to the cruise control RES switch.

On vehicles with automatic transmission, if the BCU receives an input from the gear position switch or the brake pedal switch, the BCU sends a signal to the cruise control ECU to cancel or inhibit cruise control operation.

Shift interlock (where fitted)

On automatic gearbox models, the BCU and IDM combine with an interlock relay located in the passenger compartment fuse box to operate a shift interlock solenoid, so that the gear selector lever cannot be moved out of Park until certain logical conditions have been satisfied. Operation of the interlock may be affected, if the battery becomes discharged.

Ignition key interlock (where fitted)

On automatic gearbox models, the ignition key interlock solenoid prevents removal of the ignition key from the ignition switch when the transmission gear selector is not in the Park position. The logic control operation for this is performed by the BCU.

Transfer box interlock (where fitted)

On automatic gearbox models, a transfer box interlock solenoid is controlled by the IDM to prevent transfer box shift lever being moved out of high or low range unless certain conditions have been satisfied. The IDM controls the operation of the transfer box relay which is located in the passenger compartment fuse box.

Gear position switch

A gear position switch is located on the automatic gearbox and is used to inform the BCU of the gear selector lever position. The BCU has four sensing inputs from the gear position switch contacts W, X, Y, Z, which are used to determine the gearbox drive status at any particular instance. The BCU gives an output corresponding to the gearbox status derived from the gear position switch inputs. The logic states defining the gear selector positions are listed in the table below, where Z1, Z2, Z3 and Z4 represent intermediate states which exist as the selector lever position is changed

PIN DESCRIPTION

The existence of an intermediate state causes a fault code to be detected by the BCU. To reduce the chances of the fault condition occurring while changing selector lever position, the inputs are de-bounced and only considered valid when they have existed for at least 33 ms.

Transmission neutral selector

The transmission neutral sensor provides an earth signal to the BCU when the transfer box is in neutral. The earth signal causes the BCU to operate an audible warning when the transfer box is in neutral with the ignition switched on.

Self levelling suspension and ABS

The BCU communicates with the SLABS ECU for several functions

1. An output is provided from the SLABS ECU to the BCU to provide the logic conditions for issuing the SLS audible warning.
2. The BCU receives an input from the SLABS ECU relating to the raise/ lower command from the remote handset.

Hill descent control

The BCU provides an output signal to the SLABS ECU for automatic transmission in neutral for HDC control. The BCU checks the status of the ignition and 'gearbox state' inputs and provides a 'Neutral selected' output. If the ignition is on and 'gearbox state' is Neutral, the 'Neutral selected' output is on, otherwise 'Neutral selected' is off.

Heated screens

The Heated Front Screen (HFS) is fitted for some market destinations and is operated from a non-latching switch located on the instrument pack cowl. The BCU will only allow the heated front screen to operate when the engine is running and controls the time-out period for switching the circuit off.

The heated front screen operation can also be controlled from the Automatic Temperature Control (ATC) ECU on vehicles fitted with air conditioning.

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 heated rear window can also be operated by the ATC ECU on vehicles fitted with air conditioning.

Interior courtesy lamps

The BCU controls the operation of the interior courtesy lamps. The courtesy lamps are situated in the front, mid and rear areas of the headlining.

Fuel flap actuator

The BCU provides an earth path to the fuel flap release solenoid to allow the fuel filler flap to be opened. This is only allowed if the alarm system is not set and all other conditions have been satisfied. The fuel flap release switch is located in the fascia switch pack on vehicles up to 2003 model year or in the instrument pack binnacle on vehicles from 2003 model year. The switch receives a voltage supply from the passenger compartment fuse box.

Audible warnings

The BCU can request the instrument pack to generate an audible warning in response to conditions it has detected and which need to be drawn to the driver's attention. One of six different audible warnings can be requested by the BCU.

SIGNAL DESCRIPTION

Operation

For IDM inputs which are also inputs for BCU functions, the delay before the BCU recognizes the change in input status is less than 250 ms. The BCU uses a de-bounce 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 de-bounce period of 33 ms.

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.

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.

For immobilization, 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 immobilized. 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 immobilization system. Once the immobilizer 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-mobilize 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-mobilize the vehicle.

Anti-theft alarm

The alarm system provides a warning of unauthorized 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

1. All doors and hinged panels are in the closed position.
2. Ignition key out of the ignition switch.
3. 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.

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 recognize 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 immobilization 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-mobilization 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 utilize 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

1. Pressing the lock button on the remote transmitter.
2. Locking the vehicle from the driver's door with the key.
3. Pressing the lower half of the central door lock switch.
4. Pushing the sill button down (will only lock that particular door).
5. 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

1. Driver's door open.
2. Ignition switch on.
3. Inertia switch tripped.
4. Vehicle is already superlocked.

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

The doors can be unlocked by the following methods

1. Pressing the unlock button on the remote transmitter
2. Unlocking the vehicle from the driver's door with the key.
3. Pressing the upper half of the central door locking switch (not operational if the vehicle is superlocked).
4. Pulling the interior door handles (not operational if the vehicle is superlocked).
5. 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 energize the coil of the relays for each of the door lock actuators.

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

1. Unlock request.
2. Lock request.
3. Superlock request.
4. Single point entry request.
5. 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

1. Unlock all doors enable.
2. Lock passenger and rear doors enable.
3. Superlock all doors enable.
4. 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.

Three modes of operation are available

1. Driver cancel - the front windows, rear windows and sunroof will be disabled 44 seconds after the driver's door is opened.
2. All cancel - The front windows, rear windows and sunroof will be disabled 44 seconds after any door is opened.
3. 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

1. Ignition state.
2. Driver's door open.
3. Passenger or rear door open.
4. Front right window down.
5. Front right window up.
6. Front left window down.
7. Front left window up.
8. Right window stall detect.
9. 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

1. Right window up.
2. Right window down.
3. Left window up.
4. 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

1. Ignition state.
2. Driver's door open.
3. 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 initialized 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

1. A stall condition exists (window has reached bottom of travel).
2. Window switch is repressed in either direction for more than 0.4 +/- 0.2 second.
3. The BCU has operated the motor for a period greater than 10 +/- 0.2 seconds.

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

1. The driver's door has been closed after the ignition has been switched off.
2. 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 energized the relay contacts close and power is applied to the rear window motor. If the window lift isolation switch located in the center 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.

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

1. Ignition state.
2. Engine running (link from instrument pack).
3. 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.

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

1. Ignition state.
2. Engine running (link from instrument pack).
3. 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.

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.

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.

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 utilized 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

1. Ignition state.
2. Front intermittent wiper switch.
3. 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 program can be configured to operate in one of two ways

1. Option 1 - normal.
2. Option 2 - no wipe.

The BCU checks for the following inputs

1. Ignition state.
2. Front washer pump switch.

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

1. Front wiper enable.
2. Front wash/ wipe in progress flag.

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

Rear wipers and washers

The rear wiper is initially operated for a period of 4 seconds when the rear wiper switch is pressed, to complete two full cycles. After this, the rear wiper will operate every other time the front wiper completes a wipe operation. During the wipe operation, the front and rear wipers are synchronized, and changes to the delay period during intermittent wipe will change the delay period for both front and rear wipers.

Operation of the rear washer switch causes the washer motor to operate for as long as the switch is operated. The wiper also operates while the switch is depressed and for a further 4 seconds after the switch is released.

The BCU checks for the following inputs to determine when to provide the rear wiper enable signal

1. Ignition state.
2. Rear wiper switch.
3. Front intermittent wiper rate.
4. Front intermittent wiper switch.

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

In the event of a communications link failure occurring while the rear intermittent wipe program is in operation, the rear wiper enable output is switched off.

Reverse gear wipe

The BCU changes the operation of the rear wiper when the front wiper is active and reverse gear is selected. The rear wiper operation rate used when the preconditions have been satisfied depend on the prevailing front wiper operating mode and the position of the rear wiper switch. If the rear wiper is on or the front wiper is operating at an intermittent rate when reverse gear is selected, the BCU will operate the rear wiper continuously for 4 seconds via the IDM. After the initial period, the rear wiper will operate at the same rate as the front wiper.

The BCU checks for the following inputs to determine when to provide the rear wiper enable signal if the vehicle is in reverse gear

1. Ignition state.
2. Rear wiper switch.
3. Front intermittent wiper rate.
4. Reverse gear selected.
5. Front intermittent wiper switch.
6. Front wiper switch state.
7. Front wash/ wipe in progress flag.

In the event of a communications link failure occurring while the reversing wipe is in operation, the rear wiper enable output is switched off.

Headlamp wash

The headlamp wash will only operate when the headlamps are on, and then only every third time the front windscreen wash button is pressed. When the BCU operates the headlamp washers, it activates the washer pump relay for a period of 500 ms. The BCU supplies an earth path for the coil of the power wash relay located in the engine compartment fuse box when the washer function is selected.

The BCU checks for the following inputs to determine when to provide power to the headlamp power wash relay

1. Ignition state.
2. Front washer pump switch.
3. Dipped beam.
4. Main beam state.

If the ignition switch is in the off position, the headlamp power wash relay is also held off. if the ignition state is crank, the headlamp power wash relay is switched off and the headlamp power wash counter is reset to 0.

In the event of a communications link failure occurring while the headlamp power wash relay in on, the relay remains on until the 500 ms timer has completed, then the relay is switched off.

The BCU can be programmed to operate the electric seats according to one of three options

1. Option 1 - no electric seats.
2. Option 2 - normal.
3. Option 3 - operates with ignition only.

To determine when to provide an output to the passenger and drivers seat enable relay, the BCU checks the condition of the following inputs

1. Ignition state.
2. Transit mode.
3. Driver's door open.

The electrically controlled seats are operated when the ignition switch is in position I or II or for a predetermined period when the driver's door is open. If the ignition state is in crank, the seat enable relay is off. If the ignition state is off and the driver's door open input is off, the seat enable relay is off. If the ignition state is off and the driver's door open input is on and transit mode is on, the seat enable relay output is off.

The power supply to each seat switch pack is powered from a power seat relay located on the underside of each seat frame. The feed from the relay is protected by a fuse located in a satellite fuse block located adjacent to the power seat relay. The fuse block also contains two additional fuses which are used to protect the feeds to the lumbar pump and solenoid.

With the ignition switch in position I or II or the driver's door open, the BCU provides an earth path for the coils of the LH and RH power seat relays, energizing the relays and closing the contacts. If the driver's door input signal is on for longer than 45 seconds with the ignition switched off, the seat enable relay is switched off.

The BCU supplies reference voltages for the LH and RH indicators. When the direction indicator switch is used to select the LH or RH indicator position, an earth path is completed which signals the BCU that a request for direction indicator operation has been made. The BCU then communicates this request to the IDM which supplies an earth path for the coil of the relevant relay (LH or RH indicator relay). When the relay coil is energized, the relay contacts close and a voltage supply is provided via a resistor to the relevant direction indicators. The IDM controls the timing of the flash operations by continually removing and restoring the earth path to the direction indicator relay coil.

The BCU checks for the following inputs for performing the logic operations associated with the direction indicator lamps

1. Ignition state.
2. RH indicators selected.
3. LH indicators selected.
4. Hazards selected.
5. Inertia switch hazard request.
6. One short indicator flash request (anti-theft system arming).
7. Two short indicator flash request (superlocking).
8. One long indicator flash request (anti-theft system disarming).
9. Alarm flashing indicators (anti-theft alarm triggered).

The following outputs are provided by the BCU as a result of the inputs received and the logical operations performed

1. RH indicators enable.
2. LH indicators enable.
3. Direction indicator left message (link to IDM).
4. Direction indicator right message (link to IDM).

Direction indicator lamp failure detection

The BCU uses the following logic inputs to determine if there is a direction indicator bulb failure or if the presence of a trailer is detected. The BCU uses the information to decide which output to enable at any particular instance

1. Right direction indicators requested.
2. Left direction indicators requested.
3. RH indicators current sense.
4. LH indicators current sense.

If a direction indicator bulb failure or a trailer presence is detected, the following outputs can be generated depending on the BCU logic states

1. Trailer detected.
2. Bulb failure detected.
3. Direction indicator short circuit.
4. Direction indicator relay stuck.

The BCU can be configured whether or not to provide bulb failure warnings.

When the direction indicators are operating, instrument pack direction indicators flash in sequence with the exterior direction indicators. If a failure of an indicator bulb occurs, the corresponding instrument pack indication lamp will flash quickly to warn of the problem.

The IDM monitors the current drawn through the circuit to detect for the occurrence of a lamp failure. If an indicator lamp fails, the IDM detects the drop in current drawn through the resistor and operates the indicator relay at a faster speed. The fast flash is demonstrated on the instrument pack direction indicator warning lamps to bring attention to the driver that a direction indicator bulb failure has occurred. The current sense for the related indicator lamps (RH or LH) are checked when a direction indicator request has been made that lasts for at least 160 ms. The current level sensed is relative to the number of working bulbs and determines the request generated by the BCU.

NUMBER OF WORKING BULBS

The output is signalled to the instrument pack using the serial communications link. If the hazard warning lamps are operating, both sets of direction indicators are checked using the current sensing functions to check the number of bulbs on each side of the vehicle.

If the BCU detects that a direction indicator request has not been made, but one or other of the current sense inputs indicate that current is flowing, a 'Relay stuck' output is generated.

Hazard lamps

The BCU controls the operation of the hazard warning lamps via the IDM and dedicated relays. The hazard warning lamps are activated under the following conditions

1. The vehicle is locked and the security system is set (the hazard warning lamps flash three times if the superlocking feature is used, once if not).
2. The vehicle is unlocked (the hazard warning lamps flash once for a duration of two seconds).
3. The anti-theft alarm system is triggered (the hazard warning lamps flash in phase with and for the duration of the audible warning).
4. The hazard warning switch is pressed (the hazard warning lamps flash until the hazard warning switch is pressed for a second time).
5. The inertia switch is triggered (the hazard warning lamps flash until the inertia switch has been reset).

The hazard warning lamp operation may differ dependent on market and customer configuration options.

The hazard warning lamps are operated from a latching pushbutton switch located on the fascia. When the switch is pressed, both left and right indicator lamps in the instrument pack flash to show that the hazard warning lamps are operating and all hazard warning lamps flash simultaneously. If a trailer is fitted, the ICM detects this and a trailer symbol in the instrument pack also flashes to show correct operation of the trailer direction indicators and hazard warning lamps.

The BCU supplies a reference voltage to the hazard warning switch. When the hazard warning switch is operated an earth path is completed which signals the BCU that a request for hazard lamp operation has been made. The BCU then sends a signal to the IDM via the serial data bus to communicate the request. The IDM supplies an earth path for both direction indicator relay coils simultaneously so that the hazard warning lamps are turned on concurrently. The IDM controls the timing of the flash operations by continually removing and restoring the earth path to both direction indicator relay coils simultaneously.

Courtesy headlamps

This feature activates the headlamps for 30 seconds when the lock button on the remote transmitter is held down for longer than 1 second. The headlamps will extinguish if the BCU receives either a lock or an unlock signal from the remote transmitter.

The BCU checks the status of the following inputs to determine the correct qualifying conditions for requesting courtesy headlamps

1. Ignition state.
2. Remote locking request.
3. Remote unlocking request.
4. Lazy locking request.

If the ignition is off and a lazy locking request is received, the courtesy headlamps are switched on and an internal timer is turned on in the BCU which operates for 30 seconds. If the 30 second timer expires or a request for remote locking or remote unlocking is received, the courtesy headlamps will be turned off.

When main beam is selected, the IDM also provides a signal to the instrument pack to switch on the main beam warning lamp. An additional signal 'main beam indicator disable' is used to prevent the daylight running lamps illuminating the main beam indicator when the main beam is in the daylight running lamp state and the main beam indicator disable signal is on.

Lights on alarm

The lights on alarm in the instrument pack operates when the driver's door is open and the side lamps or headlamps are on. The system uses inputs from the driver's door switch and the lighting switch to determine the logical conditions that need to occur for switching on the alarm. The BCU carries out the logic operation and communicates with the instrument pack using the serial data bus; the instrument pack will be requested to sound the alarm if the logic inputs indicate that the driver's door is open with the lights still on.

Supply voltage is provided through the lighting switch to the IDM which acts as the signal line to indicate that the lights are on for the logic circuits in the IDM and BCU. When the driver's door is opened, a second feed is supplied to the BCU through the driver's door switch to indicate the condition. In this logic condition (lights on and driver's door open) the BCU signals the instrument pack to operate the audible warning. If the lights are switched off or the driver's door is closed the logic condition will be changed and the audible warning will be switched off.

Daylight running lamps

The BCU operates the daylight running lamps (where fitted) via the IDM. The daylight running lamps option can be programmed in one of three states dependent on market/ customer requirements, these are

1. Option 1- no daylight running lamps.
2. Option 2 - on with main beam off.
3. Option 3 - on with main and dipped beam off and gearbox not in Park.

The BCU will ensure the logical conditions are satisfied for the lamps to operate under the set conditions. The BCU checks the status of the following inputs to determine the logic action for providing an output to the daylight running lamp relay

1. Main beam state.
2. Engine running (link from instrument pack).
3. Dipped beam.
4. Gearbox state.

A voltage supply is fed to the coil of the daylight running lamp relay and the IDM. When the preconditions are satisfied for daylight running lamp operation, the BCU sends a signal for the IDM to complete the circuit to earth to switch on the daylight running lamps. The logical inputs are checked to ensure that the engine is running before switching the relay to turn on the daylight running lamps. The engine running signal has to be present for at least 2 seconds before the daylight running lamp relay can be switched on.

Fog lamps

The BCU operates the rear fog lamps and the front fog lamps (where fitted) via the IDM. The BCU front fog lamp operation can be programmed to operate under one of three set conditions. The BCU will ensure the logical conditions are satisfied for the lamps to operate under the set conditions.

Front fog lamp operation is monitored by the BCU, which allows only the front fog lamps to operate when the side lamps or headlamps are on. When the side lamps, headlamps or ignition switch is turned off, the BCU also switches off the fog lamps. When the side or headlamps are switched on again, the front fog lamps will remain off unless the front fog lamp switch is pressed to resume operation. If the rear fog guard lamps are selected on, switching off the front fog lamps will also switch off the rear fog guard lamps.

When the fog lamp switch is operated, an earth path is completed and the BCU allows the fog lights to be switched on providing the logical preconditions have been satisfied. The BCU then supplies a voltage supply to the fog lamp relay, to illuminate the fog lamps.

The front fog lamps option can be programmed in one of three states dependent on market/ customer requirements, these are

1. Option 1- not fitted.
2. Option 2 - main beam no effect.
3. Option 3 - off with main beam.

The BCU checks the status of the following inputs to determine the logic action for providing an output to the front fog lamp relay

1. Ignition state.
2. Main beam state.
3. Side lamps.
4. Dipped beam.
5. Front fogs selected (press button, not latched).

If the ignition state is crank the state of the front fog relay is memorized and the relay is switched off. Pressing the front fog switch during cranking will not be recognized. When the ignition state returns to Ignition after cranking, the memorized front fog relay state is restored. If the ignition is turned off, the front fog relay is turned off.

For option 3 configuration, if the main beam is turned on the state of the front fog relay is memorized and the relay is switched off. Pressing the front fog switch while main beam is on will not be recognized. When the Main beam state returns to OFF, the memorized front fog relay state is restored.

In the event of a communications link failure while the front fog relay is on, the front fog relay will be switched off.

Rear fog lamps

The rear fog lamps operation is monitored by the BCU, which only allows the rear fog lamps to operate when the side lamps or the headlamps are on. When the side lamps, headlamps or ignition is switched off, the rear fog lamps are also switched off. When the side lamps or headlamps are switched on again, the rear fog lamps will not switch on again unless re-selected by operating the rear fog lamps switch. If front fog lamps are fitted, the rear fog lamps will be switched off if the front fog lamps are switched off.

A supply voltage to the rear fog lamps relay is provided from a fuse in the passenger compartment fuse box, then through two electronic switches in the IDM. With the lighting switch in the side lamp or headlamp position, an earth path from the coil of the rear fog lamps relay completes the circuit through the two switches in the IDM to switch the rear fog lamps on when the BCU receives a request signal from the rear fog lamps switch to turn the circuit on.

The BCU checks the status of the following inputs to determine the logic action for providing an output to the rear fog lamp relay

1. Ignition state.
2. Main beam state.
3. Dipped beam.
4. Front fogs relay.
5. Rear fogs selected (press button, not latched).

If the ignition state is crank the state of the rear fog relay is memorized and the relay is switched off. Pressing the front fog switch during cranking will not be recognized. When the ignition state returns to Ignition after cranking, the memorized rear fog relay state is restored. If the ignition is turned off, the rear fog relay is turned off.

In the event of a communications link failure occurring while the rear fog relay is on, the rear fog relay will remain on until the ignition is turned off or the dipped/ main beam is turned off.

To determine when to provide an interior courtesy lamps enable output, the BCU checks the following input conditions

1. Ignition state.
2. Transit mode.
3. Driver's door open.
4. Passenger or rear door open.

The courtesy lamps operate at full brightness when they are first switched on. The BCU then gradually dims the lamps (fade-out) before completely switching them off. Fade-out occurs over a period of two seconds following the logical control signal to turn off the lights. When a door is opened, the BCU provides earth paths from the interior lamps, the load space lamp and the ignition switch illumination. The following table lists the courtesy lamps operation and duration for holding the lamps on that occurs after the BCU has detected a condition that signals the courtesy lamps should be switched on

NUMBER OF WORKING BULBS

The BCU communicates with the instrument pack to provide a range of functions.

Odometer update

The BCU can be programmed for one of two options

1. Option 1 - no odometer error warning.
2. Option 2 - odometer error warning.

In order to provide an LCD flash request to the instrument pack via the communications link, the following inputs are checked

1. Ignition state.
2. Instrument pack odometer value (via the communications link).
3. BCU odometer value.

The function is only active when the ignition state is on. The maximum allowed value is 999,999 miles (1,608,999 km).If the instrument pack odometer value is greater than the maximum allowed value, the maximum value is assumed. The BCU odometer value is stored in EEPROM. If 16 identical values of the instrument pack odometer reading is received consecutively, the instrument pack odometer value is compared with the BCU odometer value. If the consecutive readings from the instrument pack differ, the BCU odometer value is incremented accordingly. If the BCU odometer value is less than the instrument pack odometer value by up to 10 km, the BCU odometer value is set equal to the instrument pack odometer value.

If the odometer warning option is enabled, and the contents of the instrument pack odometer value buffer is identical to, or greater than BCU odometer value +/- 10 km, the BCU sends an LED flash request to the instrument pack.

In the event of a communications link failure, this function will be unable to operate.

Gear position indicator illumination

On automatic gearbox models, two variations of illumination for the gear position indicators on the selector lever can be programmed into the BCU. In option 1, illumination is provided when the ignition is on. In option 2, illumination is enabled when the ignition is on and the side lamps are off.

Starter relay

The BCU checks the status of the following inputs and internal BCU conditions to determine whether or not to provide an output to enable the starter relay

1. AutoStart inhibit (vehicles with automatic gearbox only).
2. Security start inhibit (immobilization check).
3. Engine running (link to instrument pack).
4. EEPROM locked (internal check).
5. IDM and BCU matched.

When the BCU receives a crank signal from the ignition switch, an earth path is completed to the starter relay coil, provided that the security system has been de-activated. If the ECM has not received a valid unlock/ re-mobilize signal, the starter relay will be disengaged and the engine stopped. The BCU also receives an engine running signal from the instrument pack, so that if the ignition key is turned to the crank position while the engine is running, the starter motor relay will not be engaged.

If the logic conditions are correct to allow starter operation, the completion of the earth path from the starter relay coil to the BCU energizes the coil and the relay contacts close to supply battery power to the starter motor.

When the ignition switch is released from the crank position, the power supply feed from the ignition switch to the starter relay coil is interrupted and the relay contacts open to prevent further battery feed to the starter motor.

If a communications link failure is experienced, the BCU will be prevented from detecting the 'engine running' condition and the BCU will default to assume that the engine is not running.

The Neutral/ Reverse/ Park/ Brake selected output is used by the cruise control system. The BCU checks for the following inputs

1. Ignition on.
2. Gearbox state.
3. Brake switch activated.

For vehicles with manual transmission, Neutral/ Reverse/ Park/ Brake selected output is on if the ignition is on and brake switch activated is on. Otherwise, the Neutral/ Reverse/ Park/ Brake selected output is off.

For vehicles with automatic transmission, the Neutral/ Reverse/ Park/ Brake selected output is on if the ignition is on and brake switch activated is on, or if the ignition is on and 'gearbox state' is in Neutral, Park or Reverse. Otherwise Neutral/ Reverse/ Park/ Brake selected output is off.

On automatic gearbox models, the BCU and IDM combine to operate a shift interlock solenoid, so that the gear selector lever can only be moved when certain logical conditions have been satisfied. Operation of the interlock may be affected, if the battery becomes discharged.

When the gear selector lever is in the Park position and the ignition is off, an interlock solenoid is de-energized, locking the gear selector lever in the Park position.

The gear selector lever can only be moved from the Park position when the ignition is switched on and the brake pedal is depressed. When these conditions are satisfied, the brake pedal switch signal is received by the BCU which then signals the IDM to energize the interlock relay. When the interlock relay is energized, the interlock solenoid is operated, unlocking the gear selector lever.

When the brake pedal is released, the feed to the BCU is removed and the shift interlock solenoid is de-energized. The locking mechanism controlled by the solenoid will lock the gear selector lever once it is returned to the Park position.

The shift interlock option can be programmed in one of three states dependent on market/ customer requirements, these are

1. Option 1- not fitted.
2. Option 2 - normal operation.
3. Option 3 - inhibit transfer box.

The BCU checks the status of the following inputs to determine the logic action for employing the shift interlock solenoid

1. Brake switch activated.
2. Ignition state.
3. Gearbox state.

In the event of a communications link failure, the shift interlock solenoid enable is switched on for 1 minute every time the ignition is switched on and switched off when the ignition is turned off.

Ignition interlock (where fitted)

On automatic gearbox models, when the ignition key is inserted in the ignition switch, the ignition key-in switch contacts close to supply a signal to the BCU to indicate the presence of the key in the switch and provide a supply feed to the ignition interlock solenoid. If the gear selector lever is in a position other than Park, or the 'transfer box neutral selected' is on, the BCU will supply an earth path to complete the ignition interlock circuit and cause the interlock solenoid to be engaged. With the interlock solenoid engaged, removal of the ignition key is prevented. The BCU will open the circuit, to allow removal of the ignition key, only when the gear selector lever is in the Park position and the transfer box is in either high or low range.

The ignition key interlock option can be programmed in one of three states dependent on market/ customer requirements, these are

1. Option 1- not fitted.
2. Option 2 - normal operation.
3. Option 3 - inhibit transfer box.

The BCU checks the status of the following inputs to determine the logic action for operating the ignition key interlock solenoid

1. Transfer box neutral selected.
2. Gearbox state.
3. Transit mode.

When the transit mode is on, the ignition key interlock solenoid is off.

The transfer box interlock is controlled by the IDM to prevent transfer box shifter operation unless certain preconditions have been satisfied.

The transfer box interlock prevents the transfer box being shifted from High or Low to neutral with the ignition key removed from the ignition switch. When the BCU senses that the ignition key is removed from the ignition switch, it signals the IDM via the serial data bus. The IDM then provides an earth path for the coil of the transfer box relay, energizing the relay coil and closing the relay contacts to provide a voltage supply to the transfer box interlock solenoid.

A diode is included in the supply line to the solenoid to prevent residual current causing the solenoid to stick in the energized position.

The transfer box solenoid interlock option can be programmed in one of three states dependent on market/ customer requirements, these are

1. Option 1- not fitted.
2. Option 2 - normal operation.
3. Option 3 - inhibit transfer box.

The BCU checks the status of the following inputs to determine the logic action for employing the transfer box interlock solenoid (transfer box solenoid enable)

1. Ignition state.
2. Gearbox state.

In the event of a communications link failure occurring while the transfer box enable is on, the output will be switched off.

On automatic gearbox models, the BCU provides an output which supplies power to the automatic gearbox gear position switch. The BCU checks for the following inputs before it supplies power

1. Ignition on.
2. Auxiliary.

When the ignition is on, the feed to the gear position switch is on. When the ignition is off and auxiliary is off for more than 30 seconds, feed to the gear position switch is off.

Fuel flap release

The fuel flap release solenoid only operates when the ignition switch is switched off, the anti-theft system is not activated and the fuel flap release switch is pressed. If the BCU detects that these conditions have been satisfied, it provides a path to earth for the fuel flap solenoid, so allowing the fuel flap to be opened.

To decide the correct conditions for providing a fuel flap enable output, the BCU checks the following input conditions

1. Ignition state.
2. Perimetric alarm state.

If the battery state is not normal, the electric fuel flap enable is switched off.

The BCU can request the instrument pack to generate an audible warning in response to logic conditions which have been detected by the BCU and which need to be drawn to the driver's attention.

Seat belt warning

The BCU can be programmed to include seat belt warning using one of four options

1. Option 1 - warning on for 6 seconds.
2. Option 2 - warning on for 6 seconds or until the seat belt is fastened.
3. Option 3 - warning on for 6 seconds unless the seat belt is fastened.
4. Option 4 - no warning.

The BCU checks the status of the following inputs

1. Ignition on.
2. Seat belt fastened.

Depending on the logic conditions of the inputs, the BCU provides the following outputs

1. Audible warning No. 1 requested.
2. Seat belt not fastened warning on instrument pack (via datalink to the instrument pack).

When programmed for option 1 operation, audible warning No. 1 is requested when the ignition switch is turned from off to position II. The audible warning remains active for 6 seconds and a warning lamp on the instrument pack is illuminated for the same duration.

When programmed for option 2 operation, audible warning No. 1 is requested when the ignition switch is turned from off to position II. The audible warning remains active for 6 seconds or until the seat belt fastened signal is on and a warning lamp on the instrument pack is illuminated for the same duration.

When programmed for option 3 operation, audible warning No. 1 is requested when the ignition switch is turned from off to position II. The audible warning remains active for 6 seconds if the seat belt fastened signal is off; a warning lamp on the instrument pack is illuminated for the same duration.

In the event of a communications link failure occurring, the audible and visual warning requests are not sent to the instrument pack.

Key-in warning

The BCU can be programmed to one of two options

1. Option 1 - no timeout.
2. Option 2 - no key-in warning.

The BCU issues an audible warning No. 2 request, depending on the status of the following inputs

1. Ignition state.
2. Ignition key inserted.
3. Driver'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

1. Ignition state.
2. SLABS 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

1. Transfer box neutral selected.
2. Ignition 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

1. Driver's door open.
2. Ignition on.
3. Side lamps.
4. Dipped beam state.
5. Main 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

1. Ignition state.
2. SLABS raise request.
3. SLABS 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.

Scheme 8

Scheme 9

Scheme 10

Scheme 11

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.
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. Program and calibrate new BCU using TestBook.