2002 LAND ROVER DISCOVERY ESP

EMISSION CONTROL - TD5
17-1-4 DESCRIPTION AND OPERATION
Emission Control Systems
Engine design has evolved in order to minimise the emission of harmful by-products. Emission control systems fitted
to Land Rover vehicles are designed to maintain the emission levels within the legal limits pertaining for the specified
market.
Despite the utilisation of specialised emission control equipment, it is still necessary to ensure that the engine is
correctly maintained and is in good mechanical order, so that it operates at its optimum condition.
In addition to emissions improvements through engine design and the application of electronic engine management
systems, special emission control systems are used to limit the pollutant levels developed under certain conditions.
Two main types of additional emission control system are utilised with the Td5 engine to reduce the levels of harmful
emissions released into the atmosphere. These are as follows:
1Crankcase emission control – also known as blow-by gas emissions from the engine crankcase.
2Exhaust gas recirculation – to reduce NO
2 emissions.
Crankcase emission control
All internal combustion engines generate oil vapour and smoke in the crankcase as a result of high crankcase
temperatures and piston ring and valve stem blow-by, a closed crankcase ventilation system is used to vent
crankcase gases back to the air induction system and so reduce the emission of hydrocarbons.
Gases from the crankcase are drawn into the inlet manifold to be burnt in the combustion chambers with the fresh air/
fuel mixture. The system provides effective emission control under all engine operating conditions.
Crankcase gases are drawn through the breather port in the top of the camshaft cover and routed through the breather
hose and breather valve on the flexible air intake duct to be drawn into the turbocharger intake for delivery to the air
inlet manifold via an intercooler.
An oil separator plate is included in the camshaft cover which removes the heavy particles of oil before the crankcase
gas leaves via the camshaft cover port. The rocker cover features circular chambers which promote swirl in the oil
mist emanating from the cylinder head and camshaft carrier. As the mist passes through the series of chambers
between the rocker cover and oil separator plate, oil particles are thrown against the separator walls where they
condense and fall back into the cylinder head via two air inlet holes located at each end of the rocker cover.
The breather valve is a depression limiting valve which progressively closes as engine speed increases, thereby
limiting the depression in the crankcase. The valve is of moulded plastic construction and has a port on the underside
which plugs into a port in the flexible air intake duct. A port on the side of the breather valve connects to the camshaft
cover port by means of a breather hose which is constructed from a heavy-duty braided rubber hose which is held in
place by hose clips. A corrugated plastic sleeve is used to give further protection to the breather hose. The breather
valve is orientation sensitive, and “TOP” is marked on the upper surface to ensure it is mounted correctly.
It is important that the system is airtight so hose connections to ports should be checked and the condition of the
breather hose should be periodically inspected to ensure it is in good condition.

EMISSION CONTROL - TD5
17-1-6 DESCRIPTION AND OPERATION
The EGR modulator is located on a plate fixed to the inner wing on the RH side of the engine. The modulator is
attached to the plate by two through-studs, each with two nuts which secure the modulator assembly to a rubber
mounting which helps to reduce noise. The modulator must be mounted in the vertical orientation with the two vacuum
ports uppermost.
The modulator operation is controlled by a signal from the ECM which determines the required amount of EGR
needed in response to inputs relating to air flow and engine operating and ambient conditions. The modulator has a
black two-pin connector at its base to connect it to the ECM through the engine harness.
Each modulator features three ports:
lThe top port of the EGR modulator is identified by a white band and connects to a 'T'-piece in the vacuum line
via a small-bore brown plastic hose. On type 2 systems the brown hose is connected in parallel with the vacuum
source to the ILT modulator.
The other two ports on the 'T'-piece connects vacuum line hoses of black vinyl tubing between the vacuum pump
and the brake-servo assembly attached to the bulkhead. The vacuum pump end of the vacuum line tubing
terminates in a rubber elbow, which gives a vacuum tight seal on the suction port of the vacuum pump. The
brake-servo end of the vacuum line tubing terminates with a non-return valve in a plastic housing which plugs
into the front face of the brake-servo housing.
lThe middle port of the EGR modulator is identified by a blue band and connects to the suction port on the EGR
valve through a small-bore blue plastic hose.
lThe lower port of the EGR modulator is identified by a green band and connects to atmosphere through an in-
line filter via a small-bore green plastic hose. On type 2 models a 3 way connector is fitted to vent both modulators
through a single filter. The other port of the in-line filter vents directly to atmosphere.
The blue and brown vacuum hoses are protected by corrugated plastic sheaths. The ends of the hoses are fitted with
rubber boots to ensure vacuum tight seals at the component ports.
Inlet Throttle (ILT) Modulator
1Port to vacuum source (white band)
2Port to ILT valve (blue band)
3Port to atmosphere via in-line filter (green
band)4Harness connector (green)

EMISSION CONTROL - TD5
DESCRIPTION AND OPERATION 17-1-7
The ILT modulator is located on a plate fixed to the inner wing on the RH side of the engine below the EGR modulator.
The modulator is attached to the plate by two through-studs, each with two nuts which secure the modulator assembly
to a rubber mounting which helps to reduce noise. The modulator must be mounted in the vertical orientation with the
two vacuum ports uppermost.
The modulator operation is controlled by a signal from the ECM which determines the required ratio of exhaust gas
to fresh inlet air needed in response to inputs relating to air flow and engine operating and ambient conditions. The
modulator has a green two-pin connector at its base to connect it to the ECM through the engine harness.
The ILT valve modulator features three ports:
lThe top port is identified by a white band and connects to a 'T'-piece in the vacuum line via a small-bore brown
plastic hose where it is connected in parallel with the vacuum source line to the EGR valve modulator. The two
other ports on the 'T'-piece connect vacuum line hoses of black vinyl tubing between the vacuum pump attached
to the alternator and the brake-servo assembly attached to the bulkhead.
lThe middle port is identified by a blue band and connects to the suction port on the ILT valve through a small-
bore blue plastic hose.
lThe lower port is identified by a green band and connects to atmosphere through an in-line filter via a green
plastic hose and a three-way connector positioned in-line between the modulators and the filter. The ILT
modulator hose is connected opposite to the two parallel ports at the three-way connector which connect the vent
lines to the EGR valve modulator and the in-line filter. The other port of the in-line filter vents directly to
atmosphere.
The blue and brown vacuum hoses are protected by corrugated plastic sheaths. The ends of the hoses are fitted with
rubber boots to ensure vacuum tight seals at the component ports.
EGR Valve
1EGR valve vacuum port
2EGR valve assembly
3Gasket – EGR valve to inlet manifold
4EGR pipe connection
5Exhaust gas intake6Intake air
7EGR valve open (vacuum applied to EGR
valve)
8EGR valve closed (no vacuum to EGR valve)

EMISSION CONTROL - TD5
17-1-10 DESCRIPTION AND OPERATION
EGR systems
There are two types of exhaust gas recirculation system used with the Td5 engine dependent on legislation and
market requirements, these are type 1 and type 2.
Type 1 EGR system is fitted to all Td5's built up to the introduction of 2002 MY, except for Japanese specification
vehicles.
Type 2 EGR system is fitted to all Japanese specification vehicles and was introduced into European markets for 2002
MY to meet EU3 emission requirements. An additional feature introduced at 2002 MY is the EGR cooler, which is
bolted to the front of the cylinder head.
EGR system - type 1
This EGR system features a single modulator which is electrically controlled to modulate a vacuum source to the EGR
valve. The controlled vacuum opens and closes the valve by the amount required to ensure the optimal proportion of
exhaust gas is allowed through to the inlet manifold to be combined with the fresh air intake. Control feedback is
achieved by monitoring the mass of fresh air flowing through the mass air flow sensor.
The modulator operation is controlled by a signal from the ECM which determines the required amount of EGR
needed in response to inputs relating to air flow and engine operating and ambient conditions. The ECM is low-side
driven, sinking current returned from the vacuum modulator for switching operating condition.
The exhaust gases are routed from the exhaust manifold through a shaped metal pipe which connects to the
underside of the EGR valve. The pipe is held securely in position to the front of the cylinder head using a clamp
bracket. The EGR pipe is attached to a mating port at the front end of the exhaust manifold using two Allen screws
and at the EGR valve assembly by a metal band clamp. The two Allen screws fixing the EGR pipe to the exhaust
manifold should be replaced every time the EGR pipe is removed. Extreme care should be exercised when
removing and refitting the EGR pipe to avoid damage.
When a vacuum is applied to the EGR suction port, it causes a spindle with sealing disc (EGR valve) to be raised,
thus opening the port at the EGR pipe to allow the recirculated exhaust gas to pass through into the inlet manifold.
The valve is spring loaded so that when the vacuum is removed from the suction port the valve returns to its rest
position to tightly close the exhaust gas port.
By controlling the quantity of recirculated exhaust gas available in the inlet manifold, the optimum mix for the prevailing
engine operating conditions can be maintained, which ensures the intake gas to the combustion chambers will have
burning rate properties which will reduce the NO
x emissions to an acceptable level. Normally, full recirculation is only
applicable when the NO
x emissions are most prevalent.
EGR system - type 2
This system features twin modulators mounted one above the other on a metal plate located on the inner wing at the
RH side of the engine. The modulators are electrically controlled by the engine management system and are used to
modulate a vacuum source to the EGR valve and a supplementary Inlet Throttle (ILT) valve; the two valves are
controlled to operate in tandem. The ILT valve vacuum pot is mounted adjacent to the EGR valve housing and has a
linkage which connects to a butterfly valve mounted in front of the EGR valve at the air intake manifold.
The modulator operations are electrically controlled by signals from the engine management system which
determines the required volume of exhaust gas needed in response to inputs relating to air flow, engine operating
conditions and ambient parameters such as temperature and altitude. The engine management ECM switches on the
circuit by completing the path to ground, operating the vacuum modulators.
Pre EU3 models: The exhaust gases are routed from the exhaust manifold through a shaped metal pipe which
connects to the underside of the EGR valve. The pipe is held securely in position to the front of the engine cylinder
head using a metal clamp bracket. The EGR pipe is attached to a mating port at the front end of the exhaust manifold
using two Allen screws and at the EGR valve assembly by a metal band clamp. The two Allen screws fixing the EGR
pipe to the exhaust manifold should be replaced every time the EGR pipe is removed. Extreme care should be
exercised when removing and refitting the EGR pipe to avoid damage.

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-9
Emission Control Systems
Engine design has evolved in order to minimise the emission of harmful by-products. Emission control systems are
fitted to Land Rover vehicles which are designed to maintain the emission levels within the legal limits pertaining for
the specified market.
Despite the utilisation of specialised emission control equipment, it is still necessary to ensure that the engine is
correctly maintained and is in good mechanical order so that it operates at its optimal condition. In particular, ignition
timing has an effect on the production of HC and NO
x emissions, with the harmful emissions rising as the ignition
timing is advanced.
CAUTION: In many countries it is against the law for a vehicle owner or an unauthorised dealer to modify or
tamper with emission control equipment. In some cases, the vehicle owner and/or the dealer may even be
liable for prosecution.
The engine management ECM is fundamental for controlling the emission control systems. In addition to controlling
normal operation, the system complies with On Board Diagnostic (OBD) system strategies. The system monitors and
reports on faults detected with ignition, fuelling and exhaust systems which cause an excessive increase in tailpipe
emissions. This includes component failures, engine misfire, catalyst damage, catalyst efficiency, fuel evaporative
loss and exhaust leaks.
When an emission relevant fault is determined, the fault condition is stored in the ECM memory. For NAS vehicles,
the MIL warning light on the instrument pack will be illuminated when the fault is confirmed. Confirmation of a fault
condition occurs if the fault is still found to be present during the driving cycle subsequent to the one when the fault
was first detected.

+ ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine
management.
The following types of supplementary control system are used to reduce harmful emissions released into the
atmosphere from the vehicle:
1Crankcase emission control – also known as blow-by gas emissions from the engine crankcase.
2Exhaust emission control – to limit the undesirable by-products of combustion.
3Fuel vapour evaporative loss control – to restrict the emission of fuel through evaporation from the fuel
system.
4Fuel leak detection system (NAS only) – there are two types of system which may be used to check the
evaporative emission system for the presence of leaks from the fuel tank to purge valve.
aVacuum leak detection test – checks for leaks down to 1 mm (0.04 in.) in diameter.
bPositive pressure leak detection test – utilises a leak detection pump to check for leaks down to 0.5 mm (0.02
in.) in diameter.
5Secondary air injection system (NAS only) – to reduce emissions experienced during cold starting.
Crankcase emission control system
The concentration of hydrocarbons in the crankcase of an engine is much greater than that in the vehicle's exhaust
system. In order to prevent the emission of these hydrocarbons into the atmosphere, crankcase emission control
systems are employed and are a standard legal requirement.
The crankcase ventilation system is an integral part of the air supply to the engine combustion chambers and it is
often overlooked when diagnosing problems associated with engine performance. A blocked ventilation pipe or filter
or excessive air leak into the inlet system through a damaged pipe or a leaking gasket can affect the air:fuel mixture,
performance and efficiency of the engine. Periodically check the ventilation hoses are not cracked and that they are
securely fitted to form airtight connections at their relevant ports.
The purpose of the crankcase ventilation system is to ensure that any noxious gas generated in the engine crankcase
is rendered harmless by complete burning of the fuel in the combustion chamber. Burning the crankcase vapours in
a controlled manner decreases the HC pollutants that could be emitted and helps to prevent the development of
sludge in the engine oil as well as increasing fuel economy.

EMISSION CONTROL - V8
17-2-10 DESCRIPTION AND OPERATION
A spiral oil separator is located in the stub pipe to the ventilation hose on the right hand cylinder head rocker cover,
where oil is separated and returned to the cylinder head. The rubber ventilation hose from the right hand rocker cover
is routed to a port on the right hand side of the inlet manifold plenum chamber where the returned gases mix with the
fresh inlet air passing through the throttle butterfly valve. The stub pipe on the left hand rocker cover does not contain
an oil separator, and the ventilation hose is routed to the throttle body housing at the air inlet side of the butterfly valve.
The ventilation hoses are attached to the stub pipe by metal band clamps.
Exhaust emission control system
The fuel injection system provides accurately metered quantities of fuel to the combustion chambers to ensure the
most efficient air to fuel ratio under all operating conditions. A further improvement to combustion is made by
measuring the oxygen content of the exhaust gases to enable the quantity of fuel injected to be varied in accordance
with the prevailing engine operation and ambient conditions; any unsatisfactory composition of the exhaust gas is
then corrected by adjustments made to the fuelling by the ECM.
The main components of the exhaust emission system are two catalytic converters which are an integral part of the
front exhaust pipe assembly. The catalytic converters are included in the system to reduce the emission to
atmosphere of carbon monoxide (CO), oxides of nitrogen (NO
x) and hydrocarbons (HC). The active constituents of
the catalytic converters are platinum (Pt), palladium (PD) and rhodium (Rh). Catalytic converters for NAS low
emission vehicles (LEVs) from 2000MY have active constituents of palladium and rhodium only. The correct
functioning of the converters is dependent upon close control of the oxygen concentration in the exhaust gas entering
the catalyst.
The two catalytic converters are shaped differently to allow sufficient clearance between the body and transmission,
but they remain functionally identical since they have the same volume and use the same active constituents.
The basic control loop comprises the engine (controlled system), the heated oxygen sensors (measuring elements),
the engine management ECM (control) and the injectors and ignition (actuators). Other factors also influence the
calculations of the ECM, such as air flow, air intake temperature and throttle position. Additionally, special driving
conditions are compensated for, such as starting, acceleration, deceleration, overrun and full load.
The reliability of the ignition system is critical for efficient catalytic converter operation, since misfiring will lead to
irreparable damage of the catalytic converter due to the overheating that occurs when unburned combustion gases
are burnt inside it.
CAUTION: If the engine is misfiring, it should be shut down immediately and the cause rectified. Failure to do
so will result in irreparable damage to the catalytic converter.
CAUTION: Ensure the exhaust system is free from leaks. Exhaust gas leaks upstream of the catalytic
converter could cause internal damage to the catalytic converter.
CAUTION: Serious damage to the engine may occur if a lower octane number fuel than recommended is used.
Serious damage to the catalytic converter and oxygen sensors will occur if leaded fuel is used.
Air : fuel ratio
The theoretical ideal air:fuel ratio to ensure complete combustion and minimise emissions in a spark-ignition engine
is 14.7:1 and is referred to as the stoichiometric ratio.
The excess air factor is denoted by the Lambda symbol
λ, and is used to indicate how far the air:fuel mixture ratio
deviates from the theoretical optimum during any particular operating condition.
lWhen
λ = 1, the air to fuel ratio corresponds to the theoretical optimum of 14.7:1 and is the desired condition for
minimising emissions.
lWhen
λ > 1, (i.e. λ = 1.05 to λ = 1.3) there is excess air available (lean mixture) and lower fuel consumption can
be attained at the cost of reduced performance. For mixtures above
λ = 1.3, the mixture ceases to be ignitable.
lWhen
λ < 1, (i.e. λ = 0.85 to λ = 0.95) there is an air deficiency (rich mixture) and maximum output is available,
but fuel economy is impaired.
The engine management system used with V8 engines operates in a narrower control range about the stoichiometric
ideal between
λ = 0.97 to 1.03 using closed-loop control techniques. When the engine is warmed up and operating
under normal conditions, it is essential to maintain
λ close to the ideal (λ = 1) to ensure the effective treatment of
exhaust gases by the three-way catalytic converters installed in the downpipes from each exhaust manifold.

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-11
Changes in the oxygen content has subsequent effects on the levels of exhaust emissions experienced. The levels
of hydrocarbons and carbon monoxide produced around the stoichiometric ideal control range are minimised, but
peak emission of oxides of nitrogen are experienced around the same range.
Fuel metering
For a satisfactory combustion process, precise fuel injection quantity, timing and dispersion must be ensured. If the
air:fuel mixture in the combustion chamber is not thoroughly atomized and dispersed during the combustion stroke,
some of the fuel may remain unburnt which will lead to high HC emissions.
Ignition timing
The ignition timing can be changed to minimise exhaust emissions and fuel consumption in response to changes due
to the excess air factor. As the excess air factor increases, the optimum ignition angle is advanced to compensate for
delays in flame propagation.
Exhaust emission control components
The exhaust emission control components are described below:
Catalytic converter
1Exhaust gas from manifold
2Cleaned exhaust gas to tail pipe
3Catalytic converter outer case41st ceramic brick
52nd ceramic brick
6Honeycomb structure
The catalytic converters are located in each of the front pipes from the exhaust manifolds.

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-13
The heated oxygen sensor is an integral part of the exhaust emission control system and is used in conjunction with
the catalytic converters and the engine management control unit to ensure that the air:fuel mixture ratio stays around
the stoichiometric point of
λ = 1, where the catalytic converters are most effective. Combinations of four (NAS only)
or two heated lambda sensors are used in the exhaust system dependent on market legislation.
The heated oxygen sensor is screwed into threaded mountings welded into the top of the front exhaust pipes at
suitable locations. They are used to detect the level of residual oxygen in the exhaust gas to provide an instantaneous
indication of whether combustion is complete. By positioning sensors in the stream of exhaust gases from each
separate bank of the exhaust manifold, the engine management system is better able to control the fuelling
requirements on each bank independently of the other, so allowing much closer control of the air:fuel ratio and
optimising catalytic converter efficiency.
Two pre-catalytic converter heated oxygen sensors are mounted in the front pipes for monitoring the oxygen content
of the exhaust gas. NAS models also have two additional post-catalytic converter heated oxygen sensors in the
exhaust front pipe.
CAUTION: HO2 sensors are easily damaged by dropping, over torquing, excessive heat or contamination.
Care must be taken not to damage the sensor housing or tip.
The oxygen sensors consist of a ceramic body (Galvanic cell) which is a practically pure oxygen-ion conductor made
from a mixed oxide of zirconium and yttrium. The ceramic is then coated with gas-permeable platinum, which when
heated to a sufficiently high temperature (
≥ 350° C) generates a voltage which is proportional to the oxygen content
in the exhaust gas stream.
The heated oxygen sensor is protected by an outer tube with a restricted flow opening to prevent the sensor's
ceramics from being cooled by low temperature exhaust gases at start up. The post-catalytic sensors have improved
signal quality, but a slower response rate.
The pre-catalytic and post-catalytic converter sensors are not interchangeable, and although it is possible to mount
them in transposed positions, their harness connections are of different gender and colour. It is important not to
confuse the sensor signal pins; the signal pins are gold plated, whilst the heater supply pins are tinned,
mixing them up will cause contamination and adversely affect system performance.
Each of the heated oxygen sensors have a four pin connector with the following wiring details:
lSensor signal ground (grey wire – connects to engine management ECM)
lSensor signal (black wire – connects to engine management ECM)
lHeater drive (white wire – connects to engine management ECM)
lHeater supply (white wire – connects to fuse 2, underbonnet fuse box)
The ECM connector pins for exhaust emission control are listed in the following table:
ECM Connector 2 (C635) pin-out details for exhaust emission control system
Pin Number Function Signal Type Control
2-01 Post-cat sensor heater (RH) - NAS only Output, Drive PWM, 12 - 0V
2-07 Post-cat sensor heater (LH) - NAS only Output, Drive PWM, 12 - 0V
2-08 Post-cat sensor (RH) - NAS only Ground, Signal 0V
2-09 Pre-cat sensor (LH) Ground, Signal 0V
2-10 Pre-cat sensor (RH) Ground, Signal 0V
2-11 Post-cat sensor (LH) - NAS only Ground, Signal 0V
2-13 Pre-cat sensor heater (RH) Output, Drive PWM, 12 - 0V
2-14 Post-cat sensor (RH) - NAS only Input, Signal Analogue, 0 - 1V
2-15 Pre-cat sensor (LH) Input, Signal Analogue, 0 - 1V
2-16 Pre-cat sensor (RH) Input, Signal Analogue, 0 - 1V
2-17 Post-cat sensor (LH) - NAS only Input, Signal Analogue, 0 - 1V
2-19 Pre-cat sensor heater (LH) Output, Drive PWM, 12 - 0V