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Hope this helps
Ian
FOG LAMPS
DESCRIPTION
General
Operation of both the front and rear fog lamps is controlled by the Light Check Module
(LCM). The front fog lamps are only active when the ignition switch is in the 'ignition' position
and the fascia mounted rotary lighting switch is in the side or headlamp position.
When the lighting switch is in the side lamp position, the rear fog lamps will only operate if
the front fog lamps are operational. If the lighting switch is in the headlamp position, the rear
fog lamps can be switched on separately from the front fog lamps.
For more information on fog lamp operation, refer to the Lighting section of the System
Description and Operation Workshop Manual.
OPERATION
Front Fog Lamps
Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fusible link 3 and fuse 53 of
the passenger compartment fuse box (C0632) on an R wire. Fusible link 3 (C0589) provides
a constant battery feed to the LCM (C0937) on an R wire.
Fuse 53 (C0583) provides a constant battery feed to the ignition switch (C0099 on Td6
vehicles, C0028 on V8 vehicles) on an R wire. When the ignition switch is turned to the
'auxiliary' position, current flows across the switch (C0099 on Td6 vehicles, C0028 on V8
vehicles) to fuse 9 of the passenger compartment fuse box (C0585) on a PB wire. Fuse 9
(C0587) provides an auxiliary ignition feed to the LCM (C2040) on a PY wire. The LCM
(C2039) is earthed on an N wire.
Light Check Module
The Light Check Module (LCM) (C2040) provides a feed to the lighting switch (C0041) on a
YW wire. When front fog lamps are selected, the switch contacts close momentarily. Current
flows across the switch to the LCM on an NB wire. Sensing this, the LCM powers the front
fog lamps.
The LCM (C0937) provides a feed to the RH front fog lamp (C0513) on a YN wire. The lamp
is earthed on an N wire. The LCM (C2039) also provides a feed to the LH front fog lamp
(C0514) on a YR wire. The lamp is earthed on an N wire.
General
The exterior lighting is controlled by the Light Check Module (LCM). The LCM controls the following vehicle functions:
l Control and monitoring of exterior lamps including direction indicators and hazard warning functionality
l Illumination dimmer control of instrument pack and all interior switch illumination
l Communication and control and monitoring of trailer lighting via the trailer ECU
l Control of power supply to automatic headlamp headlamp levelling ECU (only with bi-xenon headlamps option)
l 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:
l Lighting switch for side lamps and headlamps
l Momentary push switches for front and rear fog lamps
l Steering column switch for direction indicators and main beam/headlamp flash
l Brake switch
l Momentary push switch for hazard warning.
The switches are supplied with a 10mA 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 and is detected as OFF when its
resistance is more than 10.
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.
Bulb Type Rating
Halogen headlamps – Dip beam Halogen H7U 55W
Bi-xenon headlamps – Dip beam Xenon DS2 35W
Headlamps – Main beam Halogen H7U 55W
Front fog lamps Halogen H7U 55W
Rear fog lamps Bayonet 21W
Direction indicators – front Bayonet 21W
Direction indicators – side repeater Capless 5W
Direction indicators – rear Bayonet 21W
Side lamps – front Bayonet 5W
Tail lamps Bayonet (Twin filament) 21W/5W
Brake lamps 19 LED's –
Centre High Mounted Stop Lamp (CHMSL) 20 LED's –
Number plate lamps Festoon 5W
Reverse Lamps Bayonet 6W
Front side marker lamp (NAS only) Capless 5W
Rear side marker lamp (NAS only) Capless 5W
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:
l Lighting switch for side lamps and headlamps
l Momentary push switches for front and rear fog lamps
l Steering column switch for direction indicators and main beam/headlamp flash
l Brake switch
l Momentary push switch for hazard warning.
The switches are supplied with a 10mA 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 and is detected as OFF when its
resistance is more than 10.
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 0V. If a bulb in the
circuit fails, an open circuit occurs and the MOSFET outputs a signal of 5V 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 60mA, which the LCM detects as
unsuccessful bulb illumination. The xenon control modules have a diagnsotic capability and can store fault related
codes.
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18th Nov 2010 1:00pm
