L322 Range Rover System Description and Operation
LIGHTING
86-2-12 DESCRIPTION AND OPERATION
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 continuously when the lamps are switched on by evaluating the diagnostic output of
the MOSFET switches. Cold monitoring is performed at 32 second intervals 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 diagnostic capability and can store fault related
codes.
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.
SECURITY, DESCRIPTION AND OPERATION, Description.
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.
INSTRUMENTS, DESCRIPTION AND OPERATION, Description.
Low Voltage Operation
If the battery voltage falls below 11.2V, the LCM operates the minimum lighting to preserve the remaining battery
charge.
