Range Rover P38
TRANSFER BOX
9
DESCRIPTION AND OPERATION
Temperature sensor
The temperature sensor is screwed into the rear
casing. The sensor has two Lucar connectors. One
connector is attached to an earth eyelet connector,
the other is connected to the BeCM.
When the transfer box oil reaches a temperature of
between 140 and 150
°
C (284 and 302
°
F), contacts
in the switch close, completing an earth path to the
BeCM. The BeCM uses the completed earth path as a
signal to generate a ’TRANSFER OVRHEAT’
message in the message centre. The ’TRANSFER
OVRHEAT’ message is displayed alternately with a
’REFER HANDBOOK’ message. When the transfer
box oil cools to between 126 and 134
°
C
(258 and 273
°
F), the switch contacts open and the
’TRANSFER OVRHEAT’ message is extinguished.
Transfer box ECU
Transfer box ECU
The transfer box ECU is located below the front LH
seat and is identified from the other ECU’s located
under the seat by its single 36 pin harness connector.
The connector supplies power, earth, signal and
sensor information to/from the ECU and other ECU’s
for transmission operation.
The BeCM, located below the right hand front seat,
contains its own integral fusebox. The transfer box
ECU receives a battery power supply from the BeCM
via fuse number 4. An ignition on signal is also
supplied from the BeCM via fuse 6. The ignition on
signal is supplied to different ECU connector pins for
manual and automatic transmission vehicles.
On NAS only vehicles, if a fault occurs which prevents
the transfer box moving from low to high range, the
transfer box ECU outputs a signal to the ECM which is
interpreted as an OBDII fault flag.
The transfer box ECU provides feed and return paths
to the ratio control motor to operate the motor in the
required direction. Two pins are used to supply power
to the motor in each direction. The feed is supplied
from two pins to avoid overload and heat generation
which would occur if one pin was used. A 5 V signal
current is supplied to the four motor encoder switches
which are used by the ratio control motor to determine
motor position.
Speed signals from the transfer box speed sensor are
received as an input to the transfer box ECU which
calculates whether the speed is below the threshold to
allow a range change.
Range change request signals are received from the
H-gate selector switch on automatic transmission
vehicles or the high/low switch on manual vehicles.
On automatic transmission vehicles, a park/neutral
signal is transmitted from the BeCM to the transfer
box ECU. On manual transmission vehicles, a neutral
switch located in the transmission provides an earth
signal which is used by the ECU and BeCM to
determine that the transmission is in neutral. The
park/neutral and neutral signal are used by the ECU
to allow a range change only when the transmission is
in neutral.
Outputs are provided by the transfer box ECU to the
BeCM for high and low range status. The BeCM uses
the signals for instrument pack message centre
display of range status.