2002 LAND ROVER DISCOVERY earth

EMISSION CONTROL - V8
17-2-24 DESCRIPTION AND OPERATION
Leak Detection Pump (NAS vehicles with positive pressure EVAP system leakage test only)
1Harness connector
2Leak detection pump motor
3Atmosphere connection to/from EVAP canister
4Atmosphere connection to/from air filter
5Leak detection pump solenoid valve
The fuel evaporation leak detection pump is mounted forward of the EVAP canister on a bracket fitted beneath the
vehicle on the RH side of the vehicle chassis. The leak detection pump is fixed to the bracket by three screws through
the bottom of the bracket.
A short hose connects between the atmosphere vent port of the EVAP canister and a port at the rear of the fuel
evaporation leak detection pump. The hose is secured to the ports at each end by crimped metal band clips.
An elbowed quick fit connector on the top of the fuel evaporation leak detection pump connects to atmosphere via a
large bore pipe. The pipe is routed along the underside of the vehicle chassis and up into the RH side of the engine
compartment where it connects to an air filter canister.
The leak detection pump incorporates a 3–pin electrical connector. Pin-1 is the earth switched supply to the ECM for
control of the pump solenoid valve. Pin-2 is the earth switched supply to the ECM for the operation of the pump motor.
Pin-3 is the power supply to the pump motor and solenoid valve and is switched on at system start up via the main
relay and fuse 2 in the engine compartment fusebox.
Under normal circumstances (i.e. when the leak detection pump is not operating and the solenoid is not energised),
the EVAP canister vent port is connected to atmosphere via the open solenoid valve.
The pump is operated at the end of a drive cycle when the vehicle is stationary and the ignition is switched off.
M17 0213
3
4
5
1
2

EMISSION CONTROL - V8
17-2-30 DESCRIPTION AND OPERATION
Electrical connection to the SAI vacuum solenoid valve is via a 2–pin connector. A 12V electrical power supply to the
SAI vacuum solenoid valve is provided via the Main relay and Fuse 2 in the engine compartment fusebox. The ground
connection is via the ECM which controls the SAI vacuum solenoid valve operation. Note that the harness
connector to the SAI solenoid valve is grey, and must not be confused with the harness connector to the
EVAP system purge valve which is black.
The ECM switches on the SAI vacuum solenoid valve at the same time as initiating SAI pump operation. When the
SAI vacuum solenoid valve is open, a steady vacuum supply is allowed through to open the two vacuum operated
SAI control valves. When the ECM breaks the earth path to the SAI vacuum solenoid valve, the valve closes and
immediately shuts off the vacuum supply to the two SAI control valves at the same time as the SAI pump operation
is terminated.
If the SAI vacuum solenoid valve malfunctions, the following fault codes may be stored in the ECM diagnostic
memory, which can be retrieved using 'Testbook':
SAI control valves
1Pressurised air from SAI pump
2Vacuum operated SAI control valve
3Vacuum hose from SAI vacuum solenoid valve4Pressurised air to exhaust manifold
5Protective heat sleeving
6Air delivery pipe to exhaust manifold
P-code Description
P0413SAI vacuum solenoid valve not connected, open circuit
P0414SAI vacuum solenoid valve short circuit to ground
P0412SAI vacuum solenoid valve powerstage fault - harness damage, short circuit to
battery supply voltage
M17 0205
1
3
4
4
2
6
5

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-41
Following the test, the system returns to normal purge operation after the canister vent solenoid opens. Possible
reasons for an EVAP system leak test failure are listed below:
lFuel filler not tightened or cap missing.
lSensor or actuator open circuit.
lShort circuit to vehicle supply or ground.
lEither purge or CVS valve stuck open.
lEither purge or CVS valve stuck shut or blocked pipe.
lPiping broken or not connected.
lLoose or leaking connection.
If the piping is broken forward of the purge valve or is not connected, the engine may run rough and fuelling adaptions
will drift. The fault will not be detected by the leak detection diagnostic, but it will be determined by the engine
management ECM through the fuelling adaption diagnostics.
The evaluation of leakage is dependent on the differential pressure between the fuel tank and ambient atmospheric
pressure, the diagnostic is disabled above altitudes of 9500 ft. (2800 m) to avoid false detection of fuel leaks due to
the change in atmospheric pressure at altitude.
Fuel leak detection system (positive pressure leak detection type) – NAS only
The EVAP system with positive pressure leak detection capability used on NAS vehicles is similar to the standard
system, but also includes a fuel evaporation leak detection pump with integral solenoid valve. It is capable of detecting
holes in the EVAP system down to 0.5 mm (0.02 in.). The test is carried out at the end of a drive cycle, when the
vehicle is stationary and the ignition switch has been turned off. The ECM maintains an earth supply to the Main relay
to hold it on, so that power can be supplied to the leak detection pump.
First a reference measurement is established by passing the pressurised air through a by-pass circuit containing a
fixed sized restriction. The restriction assimilates a 0.5 mm (0.02 in) hole and the current drawn by the pump motor
during this procedure is recorded for comparison against the value to be obtained in the system test. The purge valve
is held closed, and the reversing valve in the leak detection pump module is not energised while the leak detection
pump is switched on. The pressurised air from the leak detection pump is forced through an orifice while the current
drawn by the pump motor is monitored.
Next the EVAP system diagnostic is performed; the solenoid valve is energised so that it closes off the EVAP system's
vent line to atmosphere, and opens a path for the pressurised air from the leak detection pump to be applied to the
closed EVAP system.
The current drawn by the leak detection pump is monitored and checked against that obtained during the reference
measurement. If the current is less than the reference value, this infers there is a hole in the EVAP system greater
than 0.5 mm (0.02 in) which is allowing the positive air pressure to leak out. If the current drawn by the pump motor
is greater than the value obtained during the reference check, the system is sealed and free from leaks. If an EVAP
system leak is detected, the ECM stores the fault in diagnostic memory and the MIL light on the instrument pack is
illuminated.
On NAS vehicles, the ECM works on a 2 trip cycle before illuminating the MIL. On EU-3 vehicles, the ECM works on
a 3 trip cycle before illuminating the MIL.
Following the test, the solenoid valve is opened to normalise the EVAP system pressure and the system returns to
normal purge operation at the start of the next drive cycle. Possible reasons for an EVAP system leak test failure are
listed below:
lFuel filler not tightened or cap missing.
lSensor or actuator open circuit.
lShort circuit to vehicle supply or ground.
lEither purge or solenoid valve stuck open.
lEither purge or solenoid valve stuck shut.
lBlocked pipe or air filter.
lPiping broken or not connected.
lLoose or leaking connection.
If the piping is broken forward of the purge valve or is not connected, the engine may run rough and fuelling adaptions
will drift. The fault will not be detected by the leak detection test, but will be determined by the engine management
ECM through the fuelling adaption diagnostics. This test can be run from TestBook.

EMISSION CONTROL - V8
17-2-42 DESCRIPTION AND OPERATION
Secondary air injection system
When the engine is started, the engine control module checks the engine coolant temperature and if it is below 55°
C, the ECM grounds the electrical connection to the coil of the secondary air injection (SAI) pump relay.
A 12V battery supply is fed to the inertia switch via fuse 13 in the engine compartment fusebox. When the inertia
switch contacts are closed, the feed passes through the switch and is connected to the coil of the Main relay. An earth
connection from the Main relay coil is connected to the ECM. When the ECM completes the earth path, the coil
energises and closes the contacts of the Main relay.
The Main and Secondary Air Injection (SAI) pump relays are located in the engine compartment fusebox. When the
contacts of the Main relay are closed, a 12V battery supply is fed to the coil of the SAI pump relay. An earth connection
from the coil of the SAI pump relay is connected to the ECM. When the ECM completes the earth path, the coil
energises and closes the contacts of the SAI pump relay to supply 12V to the SAI pump via fusible link 2 in the engine
compartment fusebox. The SAI pump starts to operate, and will continue to do so until the ECM switches off the earth
connection to the coil of the SAI pump relay.
The SAI pump remains operational for a period determined by the ECM and depends on the starting temperature of
the engine, or for a maximum operation period determined by the ECM if the target engine coolant temperature has
not been reached in the usual time.
When the contacts of the main relay are closed, a 12V battery supply is fed to the SAI solenoid valve via Fuse 2 in
the engine compartment fusebox.
The ECM grounds the electrical connection to the SAI vacuum solenoid valve at the same time as it switches on the
SAI pump motor. When the SAI vacuum solenoid valve is energised, a vacuum is provided to the operation control
ports on both of the vacuum operated SAI control valves at the exhaust manifolds. The control vacuum is sourced
from the intake manifold depression and routed to the SAI control valves via a vacuum reservoir and the SAI vacuum
solenoid valve.
The vacuum reservoir is included in the vacuum supply circuit to prevent vacuum fluctuations caused by changes in
the intake manifold depression affecting the operation of the SAI control valves.
When a vacuum is applied to the control ports of the SAI control valves, the valves open to allow pressurised air from
the SAI pump to pass through to the exhaust ports in the cylinder heads for combustion.
When the ECM has determined that the SAI pump has operated for the desired duration, it switches off the earth paths
to the SAI pump relay and the SAI vacuum solenoid valve. With the SAI vacuum solenoid valve de-energised, the
valve closes, cutting off the vacuum supply to the SAI control valves. The SAI control valves close immediately and
completely to prevent any further pressurised air from the SAI pump entering the exhaust manifolds.
The engine coolant temperature sensor incurs a time lag in respect of detecting a change in temperature and the SAI
pump automatically enters a 'soak period' between operations to prevent the SAI pump overheating. The ECM also
compares the switch off and start up temperatures, to determine whether it is necessary to operate the SAI pump.
This prevents the pump running repeatedly and overheating on repeat starts.
Other factors which may prevent or stop SAI pump operation include the prevailing engine speed / load conditions.

ENGINE MANAGEMENT SYSTEM - TD5
18-1-8 DESCRIPTION AND OPERATION
Input/Output
ECM inputs and outputs are detailed below:
Connector C0158
Pin No. Input/Output Function Signal type Value Interfaces
A1 Output Injector 5 Analogue 0
A2 Not used
A3 Output EGR modulator Digital 0-12
A4 Not used
A5 Input FT sensor earth 0 volts 0
A6 Input MAP sensor Analogue 0-5 volts
A7 Input ECT sensor Analogue 0-5 volts
A8 Sensor supply Sensor supply 5 volts 5 volts
A9 HT pin
A10 Input AAP sensor Analogue 0-5 volts
A11 Input MAF sensor Analogue 0-5 volts
A12 Not used
A13 Input CKP sensor positive Analogue
A14 Not used
A15 Input Sensor earth 5 0 volts 0 volts
A16 Input CKP sensor screened earth 0 volts 0 volts
A17 Input Sensor earth 6 0 volts 0 volts
A18 Input Sensor earth 3 0 volts 0 volts
A19 Input FT sensor Analogue 0-5 volts
A20 Input Sensor earth 2 0 volts 0 volts
A21 Output Turbocharger wastegate
modulatorDigital 0-12 volts
A22 Output Injector common 2 Analogue 0-85 volts
A23 Output Injector common 1 Analogue 0-85 volts
A24 Output Injector 4 Analogue 0 volts
A25 Output Injector 1 Analogue 0 volts
A26 Output Injector 2 Analogue 0 volts
A27 Output Injector 3 Analogue 0 volts
A28 Not used
A29 Output Glow plug relay Analogue 0-90 volts
A30 Input Sensor earth 4 0 volts 0 volts
A31 Not used
A32 Input/Output CAN negative Digital 2.5-5 volts EAT
A33 Input High/low ratio switch Digital 0-5 volts EAT, SLABS
A34 Input IAT sensor Analogue 0-5 volts
A35 Input/Output Can positive Digital 2.5-5 volts EAT
A36 Input CKP sensor negative 0 volts 0 volts

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-9
Connector C0658
Pin No. Input/Output Function Signal type Value Interfaces
B1 Input Earth 1 0 volts 0 volts
B2 Input Earth 4 0 volts 0 volts
B3 Input Supply battery voltage 12 volts 12 volts
B4 Output Cooling fan relay Switch 12-0 volts A/C ECU
B5 Output Fuel pump relay Switch 12-0 volts
B6 Output MIL Switch 12-0 volts Instruments
B7 Output Temperature gauge Digital 0-12 volts Instruments
B8 Not used
B9 Input A/C clutch request Switch 12-0 volts A/C ECU
B10 Input Normally closed brake
switchSwitch 12-0 volts
B11 Input Cruise control SET+ switch Switch 12-0 volts
B12 Input TP sensor 1 Analogue 0- 5 volts
B13 Input Vehicle speed Digital 0-12 volts
B14 Input TP sensor supply 5 volts 5 volts
B15 Input Cruise control master switch Switch 12-0 volts
B16 Input Normally open brake switch Switch 0-12 volts
B17 Input Cruise control RES switch Switch 12-0 volts
B18 Input/Output Serial communication link Digital 0-12 volts All ECU's
B19 Output Tachometer engine speed Digital 0-12 volts Instrument
Cluster
B20 Not used
B21 Output Main relay Switch 0-12 volts
B22 Input Supply battery voltage 12 volts 12 volts
B23 Input A/C fan request Switch 12-0 volts
B24 Input Earth 3 0 volts 0 volt
B25 Input Earth 2 0 volts 0 volts
B26 Input TP sensor earth 0 volts 0 volts
B27 Input Supply 2 12 volts 12 volts
B28 Not used
B29 Output A/C relay Switch 12-0 volts
B30 Output Glow plug warning light Switch 12-0 volts Instrument
Cluster
B31 Not used
B32 Output ABS digital 0-5 volts SLABS
B33 Input Ignition Switch 0-12 volts
B34 Input Security code digital 0-5 volts
B35 Input Clutch switch Switch 12-0 volts
B36 Input TP sensor 2 Analogue 5-0 volts

ENGINE MANAGEMENT SYSTEM - TD5
18-1-10 DESCRIPTION AND OPERATION
Mass Air Flow (MAF) sensor
The MAF sensor is located in the intake system between the air filter housing and the turbocharger. The ECM uses
the information generated by the MAF to control exhaust gas recirculation (EGR).
The MAF sensor works on the hot film principal. The MAF sensor has 2 sensing elements contained within a film. One
element is controlled at ambient temperature e.g. 25
°C (77 °F) while the other is heated to 200 °C (392 °F) above
this temperature e.g. 225
°C (437 °F). As air passes through the MAF sensor the hot film will be cooled. The current
required to keep the constant 200
°C (392 °F) difference provides a precise although non-linear signal of the air drawn
into the engine. The MAF sensor sends a voltage between 0 and 5 volts to the ECM proportional to the mass of the
incoming air. This calculation allows the ECM to set the EGR ratio for varying operating conditions.
Input/Output
The MAF sensor receives battery voltage from the main relay in the engine compartment fuse box. Signal output from
the MAF sensor to the ECM is a variable voltage proportional to air drawn into the engine.
Input to the MAF sensor is via pin 5 of connector C0570 at the engine compartment fuse box. This 12 volt supply is
provided by the main relay via fuse 2 in the engine compartment fuse box. The MAF sensor receives the input voltage
at pin 3 of the sensor connector.
Output from the MAF sensor is measured at pin 11 of the ECM connector C0158. The earth path is via pin 20 of the
ECM connector C0158.
The MAF sensor can fail the following ways or supply incorrect signal:
lSensor open circuit.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lContaminated sensor element.
lDamaged sensor element.
lDamaged in wiring harness.
lMAF supplies incorrect signal (due to air leak or air inlet restriction).
In the event of a MAF sensor signal failure any of the following symptoms may be observed:
lDuring driving engine speed may dip, before recovering.
lDifficult starting.
lEngine stalls after starting.
lDelayed throttle response.
lEGR inoperative.
lReduced engine performance.
lMAF signal out of parameters.
The MIL will not illuminate in a MAF sensor failure, and the ECM will use a fixed default value from its memory.

ENGINE MANAGEMENT SYSTEM - TD5
DESCRIPTION AND OPERATION 18-1-11
Ambient Air Temperature and Pressure (AAP) sensor
The AAP sensor is located in the top of the air filter housing. It provides voltage signals relative to both ambient air
pressure and temperature to the ECM. The AAP sensor produces a voltage between 0 and 5 volts proportional to the
pressure level of the air in the air filter housing. A reading of 0 volts indicates low pressure and a reading of 5 volts
indicates high pressure. The ECM uses the signal from the AAP sensor for the following functions:
lTo maintain manifold boost pressure.
lTo reduce exhaust smoke emissions while driving at high altitude.
lControl of the EGR system.
The sensor also supplies a voltage between 0v and 5v proportional to ambient temperature. The ECM uses this signal
for the following functions:
lExhaust gas over temperature protection.
lTurbocharger overspeed protection.
Input/Output
Connector C0158 pin 8 of the ECM supplies the AAP sensor with a 5 volt power supply. The pressure output from the
AAP sensor is measured at pin 10 of the ECM connector C0158, the temperature output from the AAP sensor is
measured at pin 31. The earth path is via pin 30 of ECM connector C0158.
The AAP sensor can fail the following ways or supply incorrect signal:
lSensor open circuit.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lContaminated sensor element.
lDamaged sensor element.
lResistance in wiring harness.
In the event of an AAP sensor signal failure any of the following symptoms may be observed:
lAltitude compensation inoperative (engine will produce black smoke).
lActive boost control inoperative.
lTurbocharger boost pressure limited to 1 bar (14.5 lbf.in
2).
lEGR altitude compensation inoperative.
The MIL will not illuminate in an AAP sensor failure, and the ECM will use a fixed default value from its memory.