Operation
Operation
General
The following section describe the functionality of the individual light circuits. The control of the circuits is performed by coding data in the LCM EEPROM. This coding is programed on the production line and some coding for lamp functionality is country specific.
Direction Indicator and Hazard Warning Lamps
With the ignition switch in position I or II, the direction indicators can be operated. When the column switch is moved to the left or right direction position the direction indicator lamps are activated with a pulse rate of 640 milliseconds and a pulse duty factor of 50:50. If the operation is in the illuminated phase and the direction indicator is switched off, the flashing phase will end. If the switch position is rapidly moved to from the left position to the right position (or visa versa), the applicable direction indicator lamps are switched over immediately.
If one of the vehicle or trailer direction indicator bulbs, with the exception of the side repeater lamps, is defective, the flashing frequency is doubled.
If the ignition is in position I or II and a left or right direction indicator is active, depressing the hazard warning switch will operate the hazard warning lamps, overriding the direction indicator function. when the hazard warning lamp switch is pressed a second time, the hazard warning lamp function is deactivated and the direction indicator operation reinstated, if still selected on.
If the ignition is in position I or II and the hazard warning lamps are active, operating the column switch for the left or right direction indicators will suspend the hazard warning lamp operation and activate the selected direction indicator. When the direction indicator column switch is moved to the off position, the hazard warning function will be reinstated.
If the hazard warning lamps have been activated by an I and K Bus message to the LCM in response to a crash detection, the hazard warning lamps can be switched oft using the hazard warning lamp switch. If the hazard warning lamps have been activated by the BCU due to an anti-theft alarm trigger the hazard warning lamps can only be switched off by a deactivate message from the BCU. The hazard warning lamps will also deactivate after 5.5 minutes.
The direction indicator warning lamps and the direction indicator sound are controlled by the instrument pack. They are activated by the instrument pack on receipt of a lamp status message from the LCM. The direction indicator warning lamps and the sounder are synchronised with this message with the direction indicator lamp illumination frequency.
Parking Lamps
The parking lamp function is controlled using the direction indicator column switch. If the ignition is off and the direction indicator switch is moved to the left or right position, the selected parking lamps will be illuminated. The front parking lamp is illuminated, along with the top bulb in the rear tail lamp. On NAS vehicles the applicable side marker lamps are also illuminated. The number plate lamps and the lower bulb in the tail lamp for the selected side are deactivated. No instrument pack or fascia illumination is activated. If the ignition is on and the direction indicator switch is in the left or right position, the selected side lamps will not be activated when the ignition is subsequently switched off.
Side Lamps
If the light control switch is in the side lamp or headlamp position, the front side lamps and rear tail lamps are activated. Both the upper and lower tail lamp bulbs are active along with the number plate lamps. On NAS vehicles the side marker lamps are also active.
The instrument pack and fascia illumination remains illuminated at the brightness determined by the position of the dimmer control.
Light Control switch Illumination
When the ignition is in position I or II, the switch legends on the light control switch are illuminated at maximum brightness when the light control switch is in the 'O' (off) position. when the light control switch is rotated to the side or headlamp position the legend illumination is dimmed.
Low Beam Headlamps
The low beam headlamps are activated when the light control switch is in the headlamp position and the ignition is in position II.
High Beam Headlamps
The main beam headlamps are activated when the light control switch is in the headlamp position and the ignition is in position I or II. Moving the column switch forwards from the low beam position activates the main beam headlamps.
When the ignition is in position I or II and the column switch is moved rearwards to the headlamp flash position, the main beam lamps are activated for as long as the switch is held in this position.
If the vehicle is involved in an accident and the airbags are deployed, the crash message from the DCU also illuminates the main beam head lamps which flash at the same frequency as the hazard warning lamps.
Xenon Headlamps
The xenon bulbs illuminate when an arc of electrical current is established between two electrodes within the bulb. The xenon gas sealed in the bulb reacts to the electrical excitation and the heat generated by the current flow. The Xenon gas reacting to the controlled current flow between the electrodes produces the blue/white light.
To operate at full efficiency, the xenon bulb go through three phases of operation before full output for continuous operation is achieved. The three phases are; starting phase warm-up phase and continuous phase.
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.
In the start-up phase the bulb requires an initial high voltage starting pulse of 18000 to 28000 volts to establish the arc. This is produced by the ignites. The warm-up phase begins once the arc is established. The control modules regulate the supply to the bulbs to 2.6 A which gives a lamp output of 75 W. During this phase the xenon gas begins to illuminate brightly and the environment within the bulb stabilises ensuring a continual current flow between the electrodes. When the warm-up phase is complete, the control modules change to continuous phase. The supply voltage to the bulb is reduced and the operating power required for continual operation is reduced to 35 W.
The xenon system is controlled by the LCM, two control modules and two ignites. The control modules (one per headlamp) receive an operating voltage from the LCM when the head lamps are switched on. The control modules regulate the power supply required through the phases of start-up. The control modules also have diagnostic capability which can be accessed using TestBook/T4 via the diagnostic socket.
The ignites (one per head lamp generate the initial high voltage required to establish the arc. The ignites have integral coils which generate high voltage pulses required for start-up. Once the xenon bulbs are operating, the igniter provide a closed circuit for regulated power supply from the control modules
Front Fog Lamps
The front fog lamps are only active with the ignition switch in position II and the light control switch in the side lamp or headlamp position. When the ignition is switched off, the fog lamp selection is automatically deselected.
Rear Fog Lamps
The rear fog lamps are only active with the ignition switch in position II. With the light control switch in the side lamp position, the rear fog lamps can only be selected on when the front fog lamps are active. If the front fog lamps are subsequently switched off, the rear fog lamps are automatically deselected.
With the light control switch in the headlamp position the rear fog lamps can be activated individually irrespective of the front fog lamp status.
Brake Lamps
The brake lamps are active with the ignition switch in positions I or II. The LCM receives an input from the brake switch which is used as a signal to activate the brake lamps. When HDC is active, the ABS ECU outputs a signal on a separate hardwired connection to the LCM to activate the brake lamps when the HDC function is operating.
Reverse Lamps
The reverse lamps will operate with the ignition switch in position II. The LCM activate the reverse lamps on receipt of an message on the I Bus that reverse gear has been engaged.
Main Beam/Direction Indicator Column Control Switch
Moving the switch rearwards towards the driver, completes a ground path to the LCM The ground path is completed through a 1.2 k Ohms resistor which is sensed by the LCM. On receipt of this signal the LCM activates the main beam headlamps for as long as the switch is operated. This position is non-latching and operates with the ignition switch in position I, but without the side lamps or headlamps being switched on.
Moving the switch forwards into a latching position completes a ground path to the LCM. The ground path is completed through a 300 ohms) resistor which is sensed by the LCM. On receipt of this signal, the LCM activates the main beam headlamps. The main beam will remain active until the switch is moved rearwards again removing the ground path. This function only operates when headlamps are selected on with the light control switch and the ignition switch is in position II.
Moving the switch upwards or downwards completes a ground path to the LCM. The ground path is completed through a 1.2 k ohms resistor for the RH direction indicator or through a 300 ohms resistor for the LH direction indicators which is sensed by the LCM. On receipt of this signal the LCM activates the RH or LH direction indicators. The switch is a latching switch although the direction indicators can also be operated by lightly pushing the switch without engaging the latch. The direction indicators will remain active until the switch is moved to the central off position. The direction indicators operate with the ignition switch in position I.
With the ignition switched off this switch position also operates the selected side parking lamps. Refer to 'Parking Lamps' operation earlier in this section for details.
Automatic Head lamp Levelling (Xenon headlamps only)
The automatic headlamp levelling is only used on vehicle fitted with xenon headlamps. When the LCM detects that the ignition is in position II and the side lamps or headlamps have been selected on using the light control switch, the headlamp levelling control is activated. The headlamp levelling control is also activated when the LCM receives an 'engine running' signal on the I Bus, irrespective of the light control switch position.
When initially activated, the automatic headlamp levelling ECU cycles the stepper motors through their full range of adjustment and stops at a default position. The ECU monitors the air suspension height sensor signals to determine the vehicle angle and adjusts the headlamps accordingly. As the vehicle is driven the ECU continuously monitors the signals from the front and rear RH level sensors and also uses the speed and brake signals to determine the operation. The ECU filters rapid changes of signals from the height sensors to prevent unnecessary adjustment.
Headlamp Delay
The LCM controls a headlamp delay function which illuminates the driveway after leaving the vehicle. The headlamp delay will operate on dipped beam headlamps only regardless of the position of the column stalk switch.
The delay is operated when the ignition is switched off and the key removed with the headlamps switched on. The message centre displays a 'HEADLIGHTS ON' message accompanied by a chime from the sounder. When the light control switch is moved to the 'off' position, the message centre displays a 'HEADLIGHT DELAY' message and the dip beam headlamps are activated for a period of approximately 45 seconds. After the delay period, the LCM automatically switches off the delay function extinguishing the head lamps.
Instrument Pack Warning Lamp Illumination
The warning lamps in the instrument pack for left and right direction indicator, front and rear fog lamps and headlamp main beam are activated by the LCM via messages to the instrument pack on the I Bus. The synchronisation of the indicator warning lamps with the external lamp frequency is controlled by a cyclic transmission of the light status on the I Bus.