Description

Description

General
The exterior lighting is controlled by the Light Check Module (LCM). The LCM controls the following vehicle functions:
- Control and monitoring of exterior lamps including direction indicators and hazard warning functionality
- Illumination dimmer control of instrument pack and all interior switch illumination
- Communication and control and monitoring of trailer lighting via the trailer ECU
- Control of power supply to automatic headlamp headlamp levelling ECU (only with bi-xenon headlamps option)
- Monitoring and evaluation of check control inputs from other system ECU's and output of applicable messages in the instrument pack message centre.

The LCM is connected to the I Bus and communicates with other vehicle systems via the instrument pack. The LCM contains a microprocessor which performs the control, monitoring and evaluation functions.

Light Check Module (LCM)







The LCM is located on the RH 'A' post, behind the trim panel. The LCM is connected to the vehicle wiring harness with three multiplugs.

The LCM receives two permanent battery power supplies via the passenger compartment fusebox and power feeds from the ignition switch positions I (AUX) and II (IGN).

The lighting circuits are not protected by conventional fuses. The control circuitry within the LCM for each individual circuit can detect and isolate a problem circuit.

A monitoring system within the LCM can determine a bulb failure and indicate this to the driver via the instrument pack message centre. The following table shows the bulbs monitored by the LCM and their type and rating:

Exterior Bulb Type/Rating Table







The bulbs are driven by MOSFETS within the LCM. The LCM provides a Pulse Width Modulation (PWM) output to the front parking lamp and the tail lamp bulbs to protect the bulbs. The PWM output is rapidly switched on and off to provide bulb emulation when a bulb fails.

Input Signals for Lamp Control
The LCM receives inputs from the following switches:
- Lighting switch for side lamps and headlamps
- Momentary push switches for front and rear fog lamps
- Steering column switch for direction indicators and main beam/headlamp flash
- Brake switch
- Momentary push switch for hazard warning.

The switches are supplied with a 10 mA supply from the LCM and switch to ground when operated. The LCM detects that a switch has been operated (ON) when its closing resistance is less than 100 Ohms and is detected as OFF when its resistance is more than 10 ohms.

The LCM also receives ignition switch status via hardwired connections and also on the I and K Bus via the instrument pack.

A reverse gear engaged signal is also received on the I and K bus systems to enable the LCM to activate the reverse lamps. The trailer module also outputs a signal to inform the LCM that a trailer is or is not connected. If a trailer is connected the LCM transfers control of the trailer reverse lamps and the rear fog lamp to the trailer module.

Via the bus systems the LCM receives a hazard warning lamp activation message from the DCU via the BCU, in the event of a crash or from the BCU if the alarm system is triggered.

Circuit Protection
Operation of the lamps is performed using overload proof Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). The MOSFETs have a diagnostic output for bulb monitoring and can detect overload load interruption with the lamps switched on and short circuit to positive with the lamps switched off.

The MOSFETs are protected against short circuits removing the requirement for the lamps circuits to be protected by fuses. The MOSFETs respond to heat generated by increased current flow caused by a short circuit. Normally this would cause the fuse to blow. The MOSFETs react to the heat increase and cut the supply to the affected circuit. Once the fault has been rectified or the MOSFET has cooled the MOSFET will automatically reset and operate the circuit normally.

If an overload occurs, the current flow is dependant on the temperature of the related MOSFET and can be up to 20 times the rated current of the lamp. The MOSFET heats up and deactivates the load applied to the circuit. When the MOSFET cools the circuit is once again reactivated. This thermal cycling occurs continuously in the event of an overload occurring.

The brake switch is also monitored by the LCM. If the LCM detects a short circuit to ground in the switch circuit it activates messages to the driver in the message centre. These messages will display switch defective and LH and RH stop lamp defective. The brake switch is also monitored when the ignition is in position II. The LCM checks the acceleration speed of the vehicle (via bus messages). If the vehicle is accelerating and the brake switch is still active after 10 seconds the LCM starts a timer. If after 2 minutes the brake switch is still active and the vehicle is moving the LCM activates defective switch messages in the instrument pack message centre.

Bulb Monitoring
Bulb failure monitoring is performed by the LCM processor. The lamps are cold and warm monitored by the MOSFETs in order to detect bulb failure.

The LCM processor outputs to each MOSFET. This output switches the MOSFET to supply the required output to power the lamp circuit. The microprocessor evaluates the lamp circuits by detecting the returned signals from the controlling MOSFET.

When the bulb is functioning normally, the output signal voltage from the controlling MOSFET is 0 V. If a bulb in the circuit fails an open circuit occurs and the MOSFET outputs a signal of 5 V to the processor. The signal is interpreted as a bulb failure and generates a message which is output on the I Bus to the instrument pack. The instrument pack displays the applicable bulb failure message in the message centre to provide visual warning to the driver.

Warm monitoring is performed when the lamps are switched on by evaluating the diagnostic output of the MOSFET switches. Cold monitoring is performed when the lamps are switched off. The MOSFETs briefly switch on the lamps for approximately 1 millisecond (this is insufficient to illuminate the bulb) and checks the bulb as per warm monitoring.

Cold monitoring is not possible for the dip beam headlamps of vehicles using xenon bulbs. On these vehicles the cold monitoring of the dip beam headlamps is switched off in the LCM. The LCM detects a failed xenon bulb via a reduction in current flow to the affected headlamp's xenon control module.

When a xenon bulb fails the control module's current consumption falls to 60 mA which the LCM detects as unsuccessful bulb illumination. The xenon control modules have a diagnostic capability and can store fault related codes.

Emergency Back-Up
The LCM contains emergency back-up circuitry to provide a minimum of lighting in the event of a failure of the LCM processor or other component. The emergency circuitry is deactivated when the LCM is functioning normally by monitoring the processor clock cycling frequency. During normal operation the clock frequency is not less than 15 Hz. If the clock cycling is absent, the emergency circuitry is automatically activated. Once activated the following limited lighting functions are activated when the ignition switch is moved to position II (this is irrespective of the position of the lighting switch):
- Outer tail lamps
- Low beam headlamps
- Brake lamps and CHMSL (also activated automatically when HDC is active).

The following functions are inactive and cannot be switched on manually or automatically:
- Direction indicators
- Hazard warning lamps
- Headlamp main beam
- Headlamp flash
- Front fog lamps
- Rear fog lamps
- Number plate lamps
- Reverse lamps.

Communication with the trailer module and the I and K Buses is also inactive if the processor fails.

Alarm Indications
The LCM communicates on the I and K Buses with the BCU to display alarm visual indications for alarm arm disarm and triggered conditions. Refer to the Security section for details.

If the hazard warning lamps are active when a lock or unlock request is made, the hazard warning cycle is interrupted to allow the visual indication of the requested lock cycle. When visual indication is completed the hazard warning operation will continue.

If the vehicle is involved in crash of a severity for the DCU to initiate deployment of the airbags, the DCU outputs a hazard warning lamps on request on the K bus to the instrument pack and on the I bus from the instrument pack to the LCM. The hazard warning lamps will be activated and will continue until the DCU outputs a message to deactivate the hazard warning lamps or until the hazard warning lamp switch is pressed.

Redundant Data Storage
The LCM stores data relating to the Vehicle Identification Number (VIN), total mileage and service interval indicator. This data is received by the LCM from the instrument pack and used as a back-up in the event of instrument pack replacement.

If the LCM is to be replaced, TestBook/T4 must be connected to the vehicle and the replace LCM procedure followed to ensure that the stored data is transferred to the new unit.

Refer to the Instrument Pack section for further details of redundant data storage.

Low Voltage Operation
If the battery voltage falls below 11.2 V the LCM operates the minimum lighting to preserve the remaining battery charge.

Lighting Control Switch







The light control switch is located in the fascia between the steering column and the driver's door. The switch comprises a three position rotary switch for controlling side lamps and headlamps, a thumbwheel rheostat which manually controls the fascia and interior switch night illumination, and momentary push switches for front and rear fog lamps.

The rotary side and headlamp control switch has three connections to the LCM. One connection supplies a reference voltage, to the switch contacts. The two remaining connections supply a combination of earth paths to the LCM for the side lamp or headlamp selection contacts.

The front and rear fog lamp switches operate in a similar way completing earth paths to the LCM when the switch is pressed. The fog lamp switches are momentary, non-latching switches which briefly complete an earth path which is sensed by the LCM.

Headlamp Assembly
Two head lamps systems are available; Halogen or bi-xenon. The two types of head lamps share a common lens. NAS vehicles use a different lens to other markets but these are also common between the NAS specification halogen and bi-xenon lamps.

Halogen Headlamps







The halogen head lamps use a complex surface reflector for both the dip and main beam lighting units. This type of reflector is divided into separate parabolic segments with each segment having a different focal length. The reflector segments differ between the dip and main beam lamps to produce the correct beam 'throw' for each lamp.

Both the dip and main beam bulbs are quartz halogen with a rating of 55 W. The bulbs are retained in the headlamp unit with conventional wire retaining clips.

Bi-xenon Headlamps







The Bi-xenon headlamps use a complex surface reflector for the halogen fill in main beam only lighting unit as used on the halogen headlamp. This type of reflector is divided into separate parabolic segments, with each segment having a different focal length.

The main beam bulbs are quartz halogen with a rating of 55 W. The bulbs are retained in the headlamp unit with conventional wire retaining clips.

The bi-xenon headlamps operate as a dip beam and a main beam headlamp unit. The xenon lamp comprises a projector lens with a solenoid controlled shutter to change the beam output from dip to main beam.

The bi-xenon headlamp system is controlled by the LCM using a control module and igniter located on each headlamp to operate the xenon bulb. The control modules and igniters provide the regulated power supply required to illuminate the xenon bulbs through their start-up phases of operation.

Safety Precautions


WARNING: The xenon system generates up to 28000 volts and contact with this voltage could lead to fatality Make sure the headlamps are switched off before working on the system.


The following safety precautions must be followed when working on the xenon headlamp system:
- DO NOT attempt any procedures on the xenon headlamps when the lights are switched on
- Handling of the DS2 xenon bulb must be performed using suitable protective equipment e.g. gloves and goggles. The glass part of the bulb must not be touched
- Xenon bulbs must disposed of as hazardous waste.
- Only operate the lamp in a mounted condition in the reflector.

Bi-xenon / Halogen Beam Comparison







The bi-xenon dip/main beam head lamps use ellipsoidal technology for the lens and reflector providing improved night time visibility compared with conventional halogen head lamps. The bi-xenon headlamps provide the following benefits when compared to halogen headlamps:
- Longer bulb life - Approximately 3 to 5 times longer than a halogen bulb
- Increased light output - Xenon headlamps output 2.5 to 3 times more lumens than halogen head lamps (lumens is a measure of light energy emitted per second on a given area over a given distance.
- Blue/white light which simulates natural daylight - Xenon bulbs produce a blue/white light compared to the yellow light produced by a halogen bulb.
- Improved night time driving visibility - Xenon lamps produce a wider and brighter beam in front of the vehicle than conventional halogen bulbs.
- Lower operating temperatures
- Lower power consumption.

Xenon Headlamp Construction







The xenon headlamp unit is self contained unit located within the headlamp assembly. The unit comprises a reflector an adaptor ring, the lens, a shutter controller and the xenon bulb.

The lens is curved and provides the mounting for the xenon bulb. The bulb locates in two recesses to ensure correct alignment in the reflector and is secured with a retention ring. The retention ring locates over the bulb and is turned clockwise to lock the bulb in the holder. The bulb has a two pin connector which is also a push and turn to lock fitting.

The adapter ring is attached to the reflector and provides for the attachment of the lens. The lens is attached to the adapter ring which an internal spring clip.

The shutter controller is a solenoid which operates, via a lever mechanism, the shutter. the shutter is used to change the beam projection from dip beam to main beam and visa versa.

A mechanism is located between the reflector and the adapter ring. This mechanism rotates to blank off a portion of the beam spread to enable the vehicle to be driven in opposite drive hand markets without applying blanking decals to the headlamp lens. The beam is changed by removing the access cover at the rear of the lamp assembly and moving a small lever located near the bulb holder at the side of the reflector.

Lamp Back-Up
In the event of a dip beam headlamp and the parking lamp on the same side of the vehicle becoming defective, the front direction indicator is switched on, dimmed by PWM output from the LCM to provide temporary substitute lighting.

This will also occur when the vehicle is parked with the parking lights on. If the parking lamp bulb is defective or fails when operating the same substitute lighting strategy is provided using the indicator lamp

Crash Signal Activation
In the event of an accident of a seventy to activate and deploy the airbags the DCU requests vanous electrical operations to assist with the crash situation. The DCU requests via the bus systems to the LCM to activate the hazard warning lamps.

Headlamp Levelling (Xenon headlamps only)
The automatic headlamp levelling system automatically adjusts the vertical postioning of the head lamps to provide the optimum headlamp beam position for maximum driving visibility and preventing glare to oncoming drivers.

The system is controlled by an automatic headlamp levelling ECU located at the bottom of the LH 'A' post. The ECU is connected to and receives information from the Hall effect front and rear height sensors which are also used by the air suspension system. The ECU also receives a signal from the ABS ECU for vehicle acceleration. The ECU has diagnostic capabilities and can communicate with TestBook/T4 via the K Bus, the instrument pack and the DS2 Bus.

The levelling system is a fast response system which reacts to changes of vehicle angle when driving. The ECU receives vehicle speed signals from the ABS ECU and a brake switch signal from the LCM. These two signals are used to adjust the headlamp position to compensate for changes in vehicle attitude due to acceleration or braking.

Stepper motors, located as part of the headlamp unit, drive a threaded rod which moves the lower edge of the headlamp forward or backwards to adjust the vertical position of the headlamp beam. The stepper motors are controlled by the ECU which using the data from the height sensors determines the attitude of the vehicle and compensates for load differences at the rear of the vehicle or changing driving conditions.

Front Side and Direction Indicator Lamp Assembly







The front side and direction indicator lamp assemblies are located outboard of each headlamp assembly. The direction indicator bulbs are 21 W bayonet fitting and the side lamp bulbs are 5 W bayonet fittings.

The lamp assembly is retained by two integral plastic clips which locate in the headlamp assembly housing. A threaded shaft locates in a hole in the adjacent wing panel. A knurled nut is and washer is fitted to the threaded shaft and positively retains the lamp assembly in position. The knurled nut allows for the lamp assembly to be in or out providing adjustment to ensure flush alignment with the wing contour.

The direction indicator and side lamp bulbs are located in holders. The holders are secured in the lamp housing by rotating through 90°. Each holder has a connector to allow for connection to the electrical harness.

On NAS vehicles an additional lamp holder is used to accommodate the side marker lamp. The lamp assembly lens has a vertical section which is used as the side marker illumination required for the NAS market. The side marker lamp bulb is a 5 W bayonet fitting.

Lamp Back-Up
In the event of a lamp at the front of the vehicle becoming defective when the parking lamps are switched on the front direction indicator is switched on, dimmed by PWM output from the LCM to provide temporary substitute lighting.

This will also occur when the vehicle is parked with the parking lights on. If the parking lamp bulb is defective or fails when operating the same substitute lighting strategy is provided using the indicator lamp.

Front Fog Lamps







The front fog lamps are located in the front bumper. Each lamp is secured to three lugs in the bumper and retained with self tapping screws and fasteners. Each lamp has two adjusting screws which provide for the vertical and horizontal alignment of the beam.

The 55 W halogen bulb is located in a holder. The holders are secured in the lamp housing by rotating through approximately 10 °. The holder has a connector to allow for connection to the electrical harness.

Rear side and Direction Indicator Lamp Assembly







The rear side and direction indicator lamp assemblies are located on the outer corner of each rear wing panel.

The lamp assembly is retained by two integral plastic clips which locate in corresponding clips secured to the body panel. The assembly is further retained by two self tapping screws which are accessed from inside the taildoor aperture. To remove the assembly, after removing the screws, the assembly must be prised at two indentations to release the clips. A non-metallic tool must be used with care to avoid damage to the paint finish.

The direction indicator fog lamp and side lamp bulbs are located in a holder. The holders is secured in the lamp housing by two plastic clips. The holder has a connector to allow for connection to the electrical harness.

The upper lamp aperture is for the brake lamp and the direction indicator. The brake lamp comprises a plastic holder with contains 19 LED's. This illuminates through a circular prism lens in the centre of the lamp to display the brake lamp in a red colour. The direction indicator lamp is located behind the brake lamp LED unit. The bulb is located in a reflector unit which emits the direction indicator light around the outer diameter of the brake lamp LED assembly.

The lower lamp aperture is divided into two parts and provides for the tail lamp and the rear fog lamp The rear fog lamp uses a 21 W bulb in the lower half of the aperture. This is also used for the tail lamp operated by a PWM output from the LCM to produce a lower wattage output than the fog lamp. The upper half of the tail lamp aperture is used solely for the tail lamp and uses a 21 W / 5 W bulb. Only the 5 W filament is used for the tail lamp, with the 21 W filament not used by any function.

Lamp Back-Up
When the parking lamps are switched on and a tail lamp bulb is defective the fog lamp bulb is controlled with a PWM output from the LCM to illuminate at a dimmed level of the tail lamp.

Side Repeater Lamps







The side repeater lamps are located in the front wings, forward of the louvred air vents. The side repeater lamps are clipped into the wing aperture and can be removed by pushing forwards and pulling outwards from the wing.

The side repeater lamps use a capless 5 W bulb which is pressed into contacts in a holder. The holder is located in the lamp assembly

Hazard Warning Lamps
The hazard warning lamps use the front and rear direction indicator lamps as previously described. These are controlled by the LCM in response to a hazard warning lamp request from the fascia switch.

Crash Signal Activation
In the event of an accident of a severity to activate and deploy the airbags the DCU requests various electrical operations to assist with the crash situation. The DCU requests via the bus systems to the LCM to activate the hazard warning lamps. These will continue to operate until deselected using the fascia switch. The lamps flash at a frequency which is the same as the frequency used to flash the headlamp main beam in the same situation.

Reverse Lamps
The reverse lamps are located in the lower tail door and position at either side of the number plate. The lamps are secured in the tail door with a clip at the bottom and positively secured with a screw at the top.

Each reverse lamp uses a 6 W bayonet type bulb. The bulbs do not have a back-up strategy in the event of failure, although the LCM can detect the failure and alert the driver via the instrument pack message centre.

Number Plate Lamps
Two number plate lamps are located in the trim above the number plate in the lower tail door. The lamps are press fitted in their apertures and secured by an integral plastic clip.

Each lamp uses a 5 W festoon type bulb. The bulbs do not have a back-up strategy in the event of failure, although the LCM can detect the failure and alert the driver via the instrument pack message centre.

Daylight Running Lamps (selected markets only)
In markets which require daylight running lamps, the LCM is programed with coding which activates the dip beam or dimmed main beam head lamps when the ignition is in position II.

Daylight running lamps can only be switched on or off using textbook providing the LCM is not coded with a country specific code.

Canadian market vehicles use the main beam headlamps with a dimmed output controlled by the LCM. All other countries using daylight running lamps (Finland, Norway and Sweden) use the full power dip beam headlamps.

Main Beam/Direction Indicator Column Control Switch







The main beam/direction indicator column control switch is located on the left hand side of the steering column and controls the following functions:
- Headlamp dip/main beam
- Headlamp main beam flash
- Left/right direction indicators
- Trip computer functions (Refer to Instrument pack section for details).

The main beam on and flash functions are connected on a single wire to the LCM. The switch assembly contains resistors and the ground for each selection is passed through a different resistor for each selection. The same also applies to the direction indicators. The LCM senses the resistance on the ground wire and determines which function has been selected.