Datatek, from the RR Service Manual on lighting 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.
From the above, as I understand it, the LCM does cold and warm monitoring of all the lightbulbs, switching on the bulbs for 1 millisecond is too short to illuminate a 'normal' bulb, but what about LEDs?
The flickering only occurs when the key is at Position II and is a sequential Off and On of the LEDs at the front. It only lasts for a few seconds when I first turn the key, though I haven't checked to see if I get a flicker after every 32 seconds when the lights are turned off. I will check to see when I get a chance.
I am going to get the connections checked, but have not encountered any problems with the electrics to date.
So, do other Rangie owners with LEDs get a similar 'display' from their lights?
