2002 LAND ROVER DISCOVERY earth

ENGINE MANAGEMENT SYSTEM - TD5
18-1-30 DESCRIPTION AND OPERATION
Glow plug warning lamp
The glow plug warning lamp is located in the instrument cluster. It illuminates to alert the driver that the glow plugs
are being heated prior to the engine being started. The length of time that the lamp illuminates and the glow plugs
are operating prior to cranking is the pre-heat period, which is subject to battery voltage and ECT sensor signal
controlled by the ECM.
Input/Output
The instrument cluster supplies battery voltage to the glow plug warning lamp. The ECM provides an earth path to
illuminate the lamp. The earth path is via pin 30 of ECM connector C0658.
Glow plugs
The 4 glow plugs are located in the engine block on the inlet side, in cylinder 1 to 4. Cylinder 5 has no glow plug. The
glow plugs are a vital part of the engine starting strategy.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-31
The purpose of the glow plugs is:
lAssist cold engine start.
lReduce exhaust emissions at low engine load/speed.
The main part of the glow plug is a tubular heating element that protrudes into the combustion chamber of the engine.
The heating element contains a spiral filament that is encased in magnesium oxide powder. At the tip of the tubular
heating element is the heater coil. Behind the heater coil and connected in series is a control coil. The control coil
regulates the heater coil to ensure that it does not overheat and cause a possible failure. The glow plug circuit has its
own control relay located in the engine compartment fuse box.
Pre-heat is the length of time the glow plugs operate prior to engine cranking. The ECM controls the pre-heat time of
the glow plugs based on battery voltage and coolant temperature information via the glow plug relay.
Post-heat is the length of time the glow plugs operate after the engine starts. The ECM controls the post-heat time
based on ECT information. If the ECT fails the ECM will operate pre/post-heat time strategies with default values from
its memory. The engine will be difficult to start.
Input/Output
The glow plugs receive voltage from the glow plug relay that is controlled by the ECM. The ECM provides the earth
path for the relay coil closing the relay contacts and supplying the glow plugs with battery voltage. The supply voltage
heats the coils to approximately 1000
°C (1832 °F). The glow plug circuit is wired in parallel, the body of each glow
plug is screwed directly into the engine block which provides each glow plug with an earth path.
The glow plugs can fail in the following ways:
lHeater coil open circuit.
lControl coil open circuit.
lPoor earth quality.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lWiring loom fault.
lRelay windings open circuit.
lIncorrect relay fitted.
In the event of a glow plug failure any of the following symptoms may be observed:
lDifficult starting.
lExcessive smoke emissions after engine start.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-34 DESCRIPTION AND OPERATION
Turbocharger wastegate modulator
The turbocharger wastegate modulator is located on the ancillary bracket on the engine, and is connected by flexible
pipes to the turbocharger. The modulator controls turbocharger boost pressure by varying the pressure used to open
the turbocharger wastegate. This control is vital to ensure the turbocharger does not over boost the engine.
Input/Output
The turbocharger wastegate modulator receives battery voltage from the main relay. The ECM supplies the earth path
in the form of a pulse width modulated (PWM) signal. The PWM signal from the ECM operates the modulator at a
frequency of less than 50 Hz. This signal allows the turbocharger wastegate modulator to open and close the
wastegate. This permits a proportion of the exhaust gas to bypass the turbocharger through the wastegate, thereby
regulating boost pressure.
Input voltage to the turbocharger wastegate modulator is via the main relay.
The earth path is via a PWM signal generated at pin 21 of the ECM connector C0158.
The turbocharger wastegate modulator can fail as follows:
lOpen circuit.
lShort circuit to voltage supply.
lShort circuit to vehicle earth.
lWiring loom fault.
lConnector water ingress.
lConnector failure due to excess heat.
lComponent failure due to excess heat.
lComponent failure due to excess vibration.
In the event of a turbocharger wastegate modulator failure any of the following symptoms may be observed:
lReduced engine performance.
lIncreased engine performance.
lLack of power.
lExcess smoke.
lReduced fuel economy.
The MIL will not illuminate in the event of a turbocharger wastegate modulator failure.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-35
Cruise control master switch
The cruise control master switch is located on the dashboard. When the driver activates the switch it requests the
cruise control system to be active. The switch acts as a latching switch, on the first operation of the switch the cruise
control system is activated, when the switch is pressed again the cruise control system is de-activated. The cruise
control warning lamp is part of the switch and illuminates when the switch is activated.
Input/Output
Input to the cruise control master switch is 12 volts via the main relay. When the switch is pressed the circuit is
completed by the ECM providing an earth path for the relay via pin 15 of connector C0658 of the ECM.
The cruise control master switch can fail as follows:
lOpen circuit.
lShort circuit to voltage supply.
lShort circuit to vehicle earth.
lWiring loom fault.
In the event of a cruise control master switch failure cruise control does not operate.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-36 DESCRIPTION AND OPERATION
Cruise control set/accelerate (SET+) switch
The cruise control SET+ switch is located on the vehicle steering wheel. The switch is a momentary switch and when
pressed by the driver reacts as follows:
lRequests the cruise control to become active and set at the current road speed if not already set.
lIf the cruise control is already set, pressing the switch increases the road speed at 1 mph (1.6 km/h) intervals.
The cruise control SET+ switch will only become active and operate under the following conditions:
lThe vehicle speed must be above 22 mph (35 km/h).
lThe cruise control master switch must be 'on'.
lThe brake pedal must not be pressed.
lThe automatic transmission must be in 'drive'.
lThe clutch pedal must not be pressed.
lThe suspend switch has not been operated.
Input/Output
Input to the cruise control SET+ switch is 12 volts via the main relay. When the switch is pressed the circuit is
completed by the ECM providing an earth path for the relay via pin 11 of connector C0658 of the ECM.
The cruise control SET+ switch can fail as follows:
lOpen circuit.
lShort circuit to voltage supply.
lShort circuit to vehicle earth.
lWiring loom fault In the event of a cruise control SET+ switch failure cruise control does not operate.
Cruise control resume/suspend (RES) switch
The cruise control RES switch is located on the vehicle steering wheel. The switch is a momentary switch and when
pressed by the driver reacts as follows:
lRequests the cruise control to be suspended if it has already been set.
lRequests that cruise control is resumed at the previously set road speed.
The cruise control RES switch will only become active and operate under the following conditions:
lThe vehicle speed must be above 22 mph (35 km/h).
lThe cruise control master switch must be 'on'.
lThe brake pedal must not be pressed.
lThe automatic transmission must be in 'drive'.
lThe clutch pedal must not be pressed.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-37
Input/Output
Input to the cruise control RES switch is 12 volts via the main relay. When the switch is pressed the circuit is completed
by the ECM providing an earth path for the relay via pin 17 of connector C0658 of the ECM.
The cruise control RES switch can fail as follows:
lOpen circuit.
lShort circuit to voltage supply.
lShort circuit to vehicle earth.
lWiring loom fault.
In the event of a cruise control RES switch failure cruise control resume/ suspend operation does not operate.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-39
With the ECM in a 'Secure' state, it will not function unless an alarm system is fitted to the vehicle. A 'Secure' ECM
cannot be configured into a 'No Code' ECM.
With the ECM in a 'No Code' state, it does not require an alarm system to be fitted to allow the engine to operate. If
the ECM senses that an alarm system is fitted it will not start. A 'No Code' ECM can be configured to a 'Secure' ECM
using TestBook. A 'Secure' ECM can not be configured to a 'No Code' state.
Setting up of the ECM immobilisation configurations can only be performed using TestBook.
If a vehicle stalls immediately after starting it is possible that it has been immobilised. This means either:
lThe ECM was configured as 'No Code' but the ECM is receiving a code at its alarm input pin.
lThe ECM received an incorrect code.
lThe ECM was expecting a security code but did not receive one at its alarm input pin.
Fuel delivery/injection control
The fuel delivery/injection control delivers a precise amount of finely atomised fuel to mix with the air in the
combustion chamber to create a controlled explosion.
To precisely control fuel delivery and control fuel injection, the following input conditions must be met:
lCKP information.
lInjection timing map information.
lFT information.
lECT information.
The ECM monitors the conditions required for optimum combustion of fuel in the cylinder from the various sensors
around the engine and then compares it against stored information. From this calculation the ECM can adjust the
quantity and timing of the fuel being delivered to the cylinder.
The ECM uses CKP information as follows:
lTo calculate engine speed.
lTo determine engine crankshaft position.
Engine speed and crankshaft position allows the ECM to determine fuel injection timing.
The ECM also uses ECT information and FT sensor information to allow optimum fuel delivery and injection control
for all engine coolant and fuel temperatures.
Turbocharger control
Turbocharger control is vital to ensure the turbocharger does not over boost the engine. Within the turbocharger is a
wastegate, which when operated by the turbocharger wastegate modulator will open and close a bypass valve
regulating boost pressure.
The turbocharger wastegate modulator, via the ECM, controls boost pressure under the following conditions:
lAcceleration.
lWide open throttle.
lIdle.
lOverrun.
The turbocharger wastegate modulator receives a battery voltage supply from the main relay. The ECM supplies the
earth path in the form of a pulse width modulation (PWM) signal. This signal allows the turbocharger wastegate
modulator to open and close the wastegate. A proportion of the exhaust gas can bypass the turbocharger through
the wastegate, regulating boost pressure.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-41
In the case of a VSS failure on vehicles with automatic transmissions the ECM applies default values derived from
the EAT ECU. There is no default value for manual transmission vehicle.
The VSS can fail in the following ways:
lWiring short circuit to vehicle supply.
lWiring short circuit to vehicle earth.
lWiring open circuit.
In the event of a VSS failure any of the following symptoms may be observed:
lVehicle speed limiting disabled (manual transmission only).
lHill Descent Control (HDC) warning lamp on and audible warning.
Cruise control
All markets have a common cruise control system. The cruise control system, when activated, regulates vehicle
speed. The ECM controls the cruise control system.
Cruise control activation
Cruise control is a passive system, and must be activated by the driver. Cruise control is activated by switching on
the cruise control master switch located on the instrument panel. A LED in the switch illuminates indicating cruise
control is available. The driver must accelerate the vehicle to the desired speed using the accelerator pedal. When
the desired speed is reached, cruise control can be activated by pressing the SET+ switch.
Cruise control will only activate if the following conditions are met:
lVehicle speed is above 22 mph (35 km/h).
lThe brake pedal is not pressed.
lThe clutch pedal is not pressed (manual transmission only).
lThe transmission is not in Park, Reverse or Neutral (automatic transmission only).
The ECM receives the set signal and determines the vehicle speed provided by the SLABS ECU. The ECM then
maintains current road speed.
Cruise control cancellation
Cancelling cruise control enables the driver to regain control of the vehicle speed by using the accelerator pedal.
Cruise control is cancelled if any of the following conditions occur:
lThe brake pedal is pressed.
lThe RES switch is pressed.
lThe clutch pedal is pressed (manual transmission only).
lThe cruise control master switch is switched off.
lThe transmission is placed in Park, Neutral, or Reverse (automatic transmission only).
The ECM cancels cruise control operation and returns it to the control of the accelerator pedal.
The set speed will be stored in the ECM unless:
lThe cruise control master switch is switched off.
lThe ignition is switched off.
If cruise control is deactivated using either of the above methods, the set speed will be erased from the memory of
the ECM.