Range Rover 2. Electrical Manual - part 10

 

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Range Rover 2. Electrical Manual - part 10

 

 

DIESEL

A6

CIRCUIT OPERATION

2

Boost Pressure Sensor

The boost pressure sensor signal is used in
conjunction with the air temperature signal to
calculate volume air flow into the engine. The sensor
is located on the rear bulkhead, with the pressure
tap just after the charge air cooler. If the sensor fails,
a substitute value of 490 hPa is used by the ECM
(Z132), producing a reduction in power due to a fuel
quantity limiting to 21mg/stroke.

Throttle Position Sensor (X171)

The DDE system is a ‘Drive by Wire’ system i.e. the
throttle pedal does not directly control a throttle disc
or the amount of fuel injected into the engine, but
accelerator movements or ‘drivers request’ are
sensed and the information is passed to the ECM
(Z132). The ECM (Z132) calculates the maximum
allowable fuel quantity from the air flow into the
engine, engine speed, temperature, etc. It also
includes information from strategies such as smoke
limitation, active surge damping, automatic gear
change, fuel reduction, etc. to calculate the final
figure. When driving, if the ‘drivers request’ signal is
smaller than the maximum allowable quantity, then
the requested quantity is injected. However, if the
requested quantity is greater than the maximum
allowable, then the latter quantity is injected rather
than the driver’s demand. Therefore the Throttle
Position Sensor (X171) is very important to the
system. It is located within the cab, close to the
pedal assembly itself. The unit consists of a
potentiometer and has three outputs:

1. Throttle Position – pin 37 ECM (Z132)

The sensor outputs the pedal position to the ECM
(Z132), which uses the information as described
above.

2. Idle Position Switch – pin 25 ECM (Z132).

The sensor has a separate idle position switch which
informs the ECM (Z132) of the pedal status in the
form of a simple on/off signal. This information is
used by the ECM (Z132) to implement 



idle speed

control’ and other strategies i.e. 



overrun fuel

shut–off’.

3. Kick Down Switch.

This switch is currently not used.

Fuel Temperature Sensor

A thermistor is also located inside the injection
pump. The fuel temperature sensor signal is used to
adjust the quantity of injected fuel, especially during
temperature extremes. The signal is also used to
back up the Engine Coolant Temperature Sensor
(X126). If this sensor fails, the ECM (Z132) uses a

substitute value of 60



C and only slight effects on

fuelling may possibly be noted.

Fuel Quantity Feedback Sensor

Located within the injection pump, this sensor sends
the ECM (Z132) information regarding the actual
quantity of fuel injected. Failure of the sensor or
corrupted signals will illuminate the warning lamp
and cause the engine to stall or not start. A second
check, a plausibility check against the needle lift
sensor, also takes place.

DIESEL

A6

CIRCUIT OPERATION

3

Fuel Quantity Actuator

Once again located within the injection pump, this is
a moving magnet actuator, failure of which will cause
the engine to stall or not start as the ECM (Z132) will
activate the Fuel Shut–Off Solenoid (K111).

Injection Timing (Solenoid Valve Injection Timing
Device (K229))

This is another actuator within the injection pump.
The ECM (Z132) receives a signal from the needle
lift sensor and attempts to correct the injection timing
accordingly. If a change does not occur, then the
ECM (Z132) assumes a fault exists, activates the
warning lamp and reduces the quantity of injected
fuel.

Fuel Shut–Off Solenoid (K111)

The Fuel Shut–Off Solenoid (K111) shuts the engine
down if the ECM (Z132) detects a major fault.
Failure of the valve itself does not activate the
warning lamp, although if a short circuit occurs, the
engine will shut down.

Cruise Control

Due to the DDE system being 



drive by wire’, a

cruise control feature is supplied in the ECM (Z132)
itself. Activation is via the steering wheel switches to
a converter box and on a single line to the ECM
(Z132). Failure of the signal results in cruise control
not working.

Brake Switches

The ECM (Z132) has two brake inputs, each of
opposite polarity. Comparison of the polarity states
provides the ECM (Z132) with a brake sense (i.e. if
switch 1 high and switch 2 low going to switch 1 low
and switch 2 high) and so cancels cruise control. If
both switches are the same polarity, the ECM (Z132)
senses a fault and does not allow cruise control.

Vehicle Speed Signal

The ECM (Z132) takes this signal from the
Anti–Lock Brake System ECU (Z108) and uses the
information for cruise control and 



active surge

damping’. Failure of the signal results in cruise
disallowed and temporary lack of surge damping (i.e.
hard acceleration will cause the vehicle to surge
slightly). After 10 sec. a substitute value of 150 km/h

is used. Surging will reduce so as to be hardly
noticeable.

Theft Alarm

The ECM (Z132) has a simple on/off input regarding
the theft alarm. The ECM (Z132) will not allow the
engine to start once activated and will kill the engine
if activated up to 300 RPM (programmable). Over
300 RPM, the engine is unaffected.

Relays

The DDE engine management system on the diesel
vehicles uses four relays:

ECM (Z132) power supply (main relay), glow plug
relay, starter motor relay and fuel pump relay. Two
are located in the fuse box and two in the ECM
(Z132) box behind the battery.

DIESEL

A6

CIRCUIT OPERATION

4

Main Relay

Located in the ECM (Z132) box, this relay supplies
the power feed to the ECM (Z132). It is controlled via
the Ignition Switch (X274) in position II.

Glow Plug Relay (Z135)

The Glow Plug Relay (Z135) takes a feed directly
from the battery and, on initialisation via the ECM
(Z132), supplies current to each of the six glow plugs
(one per cylinder) to aid cold starting. The glow time
is controlled via the ECM (Z132) which also monitors
the relay and illuminates the glow plug indicator lamp
for the duration of the glow time. This relay is
relatively large and is located with the main relay
next to the ECM (Z132).

Starter Motor Relay

This relay is also ignition key controlled, activated
with the key in the ignition III position only. Releasing
the key after cranking cuts supply to the relay and
switches off the starter motor.

Fuel Pump Relay

The fuel pump relay is pulled in when the starter
motor is activated, the earth path provided by the
alternator output. When the engine is running, the
starter motor is deactivated, supplying an earth path
while the generator supplies a feed i.e. a polarity
reversal.

ECM (Z132)

If the ECM (Z132) itself is not working, the entire
engine management system will cease to operate,
i.e. no fuel, tacho reading, etc.

DIESEL

A6

5

CIRCUIT DIAGRAM

REV: 07/98

30

F 37

20 A

P125a
Engine
Compartment
Fuse Box

[13] A/C

Condenser
Fan 1 Relay

[14] A/C

Condenser
Fan 2 Relay

[15] Ignition

Relay

[18] A/C Control

Relay

[19] Engine

Main
Control
Relay

RL19

[19]

Not used

Shorting Link 5

2

RL15

[15]

5

2

1

3

RL18

[18]

3

1

5

4

RL14

[14]

5 C575

Not used

8

C173

3

C575

4

C176

30

F 26

20 A

8

C575

RL13

[13]

4

Z238
Body Electrical
Control Module
(BECM)

9

C120

W

RW

Heating and
Ventilation

YB

S572

E574

A

A6-6

1

C587

2

C587

K229
Solenoid Valve,
Injection Timing
Device

W

10

C572

Z132
Engine Control
Module (ECM)

17

16

44

B

A6-9

K217
Fuel Heater

1

C592

3

2

C592

R

S571

B

See Ground
Distribution

18

E574

See Ground
Distribution

19

C572

B

B

2

F

A6-15

Partial

 

 

 

 

 

 

 

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