Range Rover P38
ELECTRICAL
23
DESCRIPTION AND OPERATION
The electric seat operation is controlled by the BeCM
via the seat outstations. The BeCM receives input
information from the outstations for the selected
functions. It then outputs the appropriate command
signals, via the serial data bus, to the applicable
outstation, which then operates the selected function.
Power Mirrors
The power mirrors operate with the ignition in position
I or II. The mirrors are operated by a multifunction
direction switch and a separate switch to select the
left or right hand mirror. Both switches are located on
the centre console switch panel.
When the mirror selection switch is in the left or right
hand mirror position, the switch provides an earth path
which the BeCM interprets as left or right hand mirror.
When the direction switch is operated, an appropriate
signal is sent from the centre console switch
outstation, via the serial data bus, to the BeCM. The
BeCM interprets the signal and outputs the
appropriate signal, via the serial data bus, to the
applicable door outstation to activate the output and
operate the mirror in the required direction. The
direction of each motor is changed by reversing the
polarity of the outputs from the door outstation.
When the ignition is in position II and the engine is
running, the door mirrors will operate constantly or
when mirror movement is requested.
The door mirrors have a reverse dip function. When
the ignition is in position II and reverse gear is
selected, the BeCM senses the earth path completed
by the reverse gear switch, and outputs the
appropriate signals to the applicable door outstation to
operate the motors to drive the applicable mirror to its
preset reverse position.
Rear View Mirror
On vehicles fitted with an automatic photochromic rear
view mirror, the BeCM provides a 12 V output to the
mirror. The mirror automatically adjusts the brightness
of the reflected light.
When reverse gear is selected, the BeCM senses the
earth path completed by the reverse gear switch and
outputs a signal of less then 1.0 V to the rear view
mirror. When the mirror receives the low output, it
restores the mirror to normal brightness to aid
reversing.
Instrument Pack
The BeCM communicates with the instrument pack
via a digital serial data bus. The use of the serial data
bus greatly reduces the number of wires which would
normally be required between the instrument pack
and the BeCM. All the wires in the data bus are
duplicated to increase the reliability of the
connections.
The speed signal, sounder, tachometer signal and the
power supply each have their own dedicated lines. All
other communications are directed via the data bus.
Electronic Air Suspension (EAS)
The BeCM communicates with the EAS ECU via
hardwired connections. The BeCM provides outputs to
the EAS ECU for road speed, engine speed,
park/handbrake status and door open signals.
The BeCM receives inputs from the EAS ECU for
warning lamp control and message centre displays.
See FRONT SUSPENSION, Description and
operation.
Transfer Box ECU
The BeCM communicates with the transfer box ECU
via hardwired connections. The BeCM receives signal
information from the transfer box ECU with regard to
the range selected via three status lines. The BeCM
processes this information and illuminates warning
lamps and/or generates messages for the instrument
pack message centre as applicable.
The messages generated vary between manual and
automatic transmission vehicles.
See TRANSFER
BOX, Description and operation.