Range Rover 2. Electrical Manual

CRUISE CONTROL

TROUBLESHOOTING

PROBLEM CAUSE

CONDITIONS

Ignition Switch

Position: II

Y, YG

CONDITIONS

Ignition Switch

Position: 0

RESULTS

Wire

Body Electrical Control
Module (BECM)

PROBLEM CAUSE

OY, YO Wire

Turn a drive wheel by hand

RESULTS

Z132
Engine Control Mod-
ule (ECM)

C572

Less than 1 ohm

Z132
Engine Control
Module (ECM)

C572

C241D

Z249
Cruise Control Converter/
Inverter Module

Fluctuating

CRUISE CONTROL

TROUBLESHOOTING

PROBLEM CAUSE

CONDITIONS

Ignition Switch

Position: 0

YR, W Wire

B, PB

Wire

Rotary Coupler

PROBLEM CAUSE

YS, R Wire

-
- Rotary Coupler

Steering Wheel Switches

PROBLEM CAUSE

Cruise Control Converter/
Inverter Module

RESULTS

Steering Wheel Switches

On
Off

Less than 1 ohm
More than 10K ohms

=
=

RES/DECEL Switch

Z249
Cruise Control Con-
verter/Inverter Mod-
ule

C241D

Steering Wheel Switches

CONDITIONS

Ignition Switch

Position: 0

RESULTS

Steering Wheel Switches

On
Off

Less than 1 ohm
More than 10K ohms

=
=

SET/ACCEL Switch

Z249
Cruise Control Con-
verter/Inverter Mod-
ule

C241D

Body Electrical Control
Module (BECM)

TRANSFER GEARBOX

CIRCUIT OPERATION

CIRCUIT OPERATION

Interface to transfer motor inside Transfer Box
(X313)

The Transmission Gearbox Control Unit (Z256) has
a seven wire interface to the Transfer Motor inside
the Transfer Box (X313), consisting of the four motor
position switches, the ground for the switches and
the drives to move the motor one way or the other.

Motor Position Switches–

pins 17, 32, 33, 7

The Transmission Gearbox Control Unit (Z256)
reads the position of the motor in the form of a
binary Gray Code.

So the Transmission Gearbox Control Unit (Z256)
can find out in which gear the Transfer Box (X313) is
in and where the motor should move to, to engage
the desired range. If the Transfer Box (X313) moves
outside the normal modes (e.g. Left of High) then the
Transmission Gearbox Control Unit (Z256) can move
the motor back to the correct position.

Motor Position Switch ground–

pin 19

The switches on the transfer box motor are
referenced to pin 19, i.e. if there is a problem with
the harness to pin 19 then the Transmission
Gearbox Control Unit (Z256) will not be able to
assess where the transfer motor is and so will not
move the motor.

Motor drive Clockwise (pins 25, 26) and Counter
Clockwise (pins 1, 2)

The Transmission Gearbox Control Unit (Z256)
receives signals from the motor position switches,
the drivers request, the vehicle speed and the
transmission neutral signal and, when the
parameters are correct, powers the motor from one
mode to another via the motor drives. This is actually
a single wire interface for each direction which is
split down to two wires at the Transmission Gearbox
Control Unit (Z256) to help pass the current though
two pins rather than one. If there is a problem with
either the motor drives or the harness, then the
motor will not move and a range change will not be
possible.

Vehicle Speed Sensor–

pins 13, 30

The Transmission Gearbox Control Unit (Z256)
senses how fast the vehicle is travelling, compares
this speed to the value stored in the memory and
decides if a range change is allowed. Presently the
shift speeds are set at 5 mph High to Low and Low
to High on vehicles with an automatic transmission

and 15 mph Low to High on vehicles with a manual
transmission.

Interface to BeCM (Z238)

High, Low and Neutral Status Lamps
–

pins 35, 14, 36

The Transmission Gearbox Control Unit (Z256)
informs the BeCM (Z238), which informs the
Instrument Pack (Z142), about the range the vehicle
is in via three status lamps.

When a range change is requested, the desired
range will flash up on the display (i.e. “HIGH”) and
continue flashing until the range change is achieved.
When complete, the range message will switch to
constant and be displayed for a few seconds.

If a range change is requested and not all of the
conditions are satisfied then the desired range
message will flash and continue flashing until all of
the parameters are satisfied or the request is
removed.

If the transfer box neutral is selected then, after a
five second safety delay, the Transfer Box (X313)
moves to neutral and the display shows “NEUTRAL”.

The High and Low status lamp signals also pass
information to the H–Gate and the Auto Gear Box
Control Unit (Z255).

Interface to Engine Control Module
(ECM) (Z132)

On North American Specification (NAS) vehicles, the
inability of the Transfer Gear Box ECU (Z256) to
move into the High range is flagged over the fault
output line. A fault will also be flagged in the event of
a speed sensor failure or incorrect transfer motor
position information. The Malfunction Indicator Lamp
(MIL) will illuminate if a fault is recorded on two
successive journeys.

TRANSFER GEARBOX

CIRCUIT OPERATION

Neutral Switch (X308) or Clutch Switch–

pin 34

A shift between ranges is possible when the
transmission is in neutral. The Transmission
Gearbox Control Unit (Z256) senses this via a
Park/Neutral Switch (X308) on automatic
transmission vehicles and via either a clutch switch
or a lever neutral switch on manual transmission
vehicles. This signal is passed via the BeCM (Z238).

Interface to “H– Gate”–

pin 35, 15 (automatic

transmission only)

The H–Gate gets the range information via a High
and Low status signal from the output of the
Transmission Gearbox Control Unit (Z256);
e.g. when the vehicle is in High then the High side of
the “H” is illuminated. When a range change to Low
is requested, the Low side of the “H” starts to flash
whilst the High side stays constant. When Low range
is obtained then the flashing light on the Low side
changes to constant and the High side light goes off.

If a range change is requested and not all of the
conditions are satisfied, then the current range will
stay illuminated and the desired range will flash and
continue flashing until all of the parameters are
satisfied or the request is removed.

If the gear lever is placed in the neutral position for
the gearbox and the transfer box then, after a five
second safety delay, the transfer box moves to
neutral and the lights on both side of the “H” are
extinguished.

Interface to Auto Gear Box Control Unit (Z255)
– pin 35

The High/Low signal to the Auto Gear Box Control
Unit (Z255) comes from the High range status lamp.
If the Auto Gear Box Control Unit (Z255) does not
receive the range information, then an incorrect gear
change mode could be selected, i.e. Manual rather
than Sport in High range and vice versa in Low
range. Also, the shift strategy is different between
the Economy modes of High and Low and so poor
shift quality could result.

Automatic Selector Park Interlock

When the gear selector lever is in the park position,
the shift interlock solenoid is deenergized and
prevents the selector from being moved to another
gear. To free the selector, the Ignition Switch (X134)
must be in position II and the brake pedal must be
depressed.

Current is then supplied to the solenoid through the
PR wire via fuse 13. The solenoid is grounded using
the B wire to the console ground E621.

The solenoid is now energised, freeing the selector.
The solenoid is energised continuously whilst the
selector lever is in any position other than park and
the Ignition Switch (X134) is in position II.

Range Rover 2. Electrical Manual - part 21