1999 LAND ROVER DISCOVERY engine

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-27
The ECM connector and pins pertinent for secondary air injection are listed in the following table:
Secondary Air Injection System Components
The secondary air injection (SAI) system components (where fitted) are described below:
Secondary Air Injection (SAI) Pump
1SAI pump cover
2Foam filter3SAI pump
4Pressurised air to exhaust manifolds
The SAI pump is attached to a bracket at the rear RH side of the engine compartment and is fixed to the bracket by
three studs and nuts. The pump is electrically powered from a 12V battery supply via a dedicated relay and supplies
approximately 35kg/hr of air when the vehicle is at idle in Neutral/Park on a start from 20°C (68°F).
Air is drawn into the pump through vents in its front cover and is then passed through a foam filter to remove
particulates before air injection. The air is delivered to the exhaust manifold on each side of the engine through a
combination of plastic and metal pipes.
Connector / Pin No. Description Signal type Control
C0635-23 Main relay output Output drive Switch to ground
C0636-4 Secondary air injection vacuum solenoid
valve controlOutput, drive Switch to ground
C0636-16 Secondary air injection pump relay control Output drive Switch to ground
C0636-21 Coolant temperature (ECT) sensor Ground 0V
C0636-22 Coolant temperature (ECT) sensor Input signal Analogue 0 - 5V
C0637-20 MIL "ON" Output drive Switch to ground
M17 0204
1
4
2
3

EMISSION CONTROL - V8
17-2-28 DESCRIPTION AND OPERATION
The air delivery pipe is a flexible plastic type, and is connected to the air pump outlet via a plastic quick-fit connector.
The other end of the flexible plastic pipe connects to the fixed metal pipework via a short rubber hose. The part of the
flexible plastic pipe which is most vulnerable to engine generated heat is protected by heat reflective sleeving. The
metal delivery pipe has a fabricated T-piece included where the pressurised air is split for delivery to each exhaust
manifold via the SAI control valves.
The pipes from the T-piece to each of the SAI control valves are approximately the same length, so that the pressure
and mass of the air delivered to each bank will be equal. The ends of the pipes are connected to the inlet port of each
SAI control valve through short rubber hose connections.
The T-piece is mounted at the rear of the engine (by the ignition coils) and features a welded mounting bracket which
is fixed to the engine by two studs and nuts.
The foam filter in the air intake of the SAI pump provides noise reduction and protects the pump from damage due to
particulate contamination. In addition, the pump is fitted on rubber mountings to help prevent noise which is generated
by pump operation from being transmitted through the vehicle body into the passenger compartment.
If the secondary air injection (SAI) pump is found to be malfunctioning, the following fault codes may be stored in the
ECM diagnostic memory, which can be retrieved using Testbook/T4:
NOTE: Refer to 'SAI System Fault Finding' and 'Checking Malfunctions on SAI System' at the end of this section to
determine root cause of fault codes.
NOTE: The electrical test of the SAI pump powerstage only indicates that there is a problem with the relay or the
power supply to the relay. It does not indicate the state of the SAI pump itself (i.e. broken or not connected).
As a result of a SAI pump powerstage malfunction, other fault codes may also become stored in the ECM memory.
These may include the following P codes.
NOTE: A malfunction of the SAI pump powerstage is logically expected to result in both engine banks reporting the
same fault.
NOTE: Refer to 'SAI System Fault Finding' and 'Checking Malfunctions on SAI System' at the end of this section to
determine root cause of fault codes.
Secondary Air Injection (SAI) Pump Relay
The secondary air injection pump relay is located in the engine compartment fusebox. The engine control module
(ECM) is used to control the operation of the SAI pump via the SAI pump relay. Power to the coil of the relay is supplied
from the vehicle battery via the main relay and the ground connection to the coil is via the ECM.
Power to the SAI pump relay contacts is via fusible link FL2 which is located in the engine compartment fusebox.
P-code Description
P0418Secondary Air Injection System – Relay 'A' circuit malfunction (SAI pump
powerstage fault, e.g. - SAI pump relay fault or relay not connected / open circuit /
harness damage).
P-code Description
P1412Secondary Air Injection System – Malfunction Bank 1 LH (Insufficient SAI flow
during passive test)
P1414Secondary Air Injection System – Low air flow Bank 1 LH (Insufficient SAI flow
during active test)
P1415Secondary Air Injection System – Malfunction Bank 2 RH (Insufficient SAI flow
during passive test)
P1417Secondary Air Injection System – Low air flow Bank 2 RH (Insufficient SAI flow
during active test)

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-29
Secondary Air Injection (SAI) Vacuum Solenoid Valve
1Vacuum port to intake manifold
(via vacuum reservoir)
2SAI vacuum solenoid valve
3Electrical connector4Vacuum port to vacuum operated SAI control
valves
5Purge valve clip
6Mounting bracket
The SAI vacuum solenoid valve is located at the rear LH side of the engine and is electrically operated under the
control of the ECM. The SAI vacuum solenoid valve is mounted on a bracket together with the EVAP system purge
valve.
Vacuum to the SAI vacuum solenoid valve is provided from the intake manifold depression via a vacuum reservoir. A
small bore vacuum hose with rubber elbow connections at each end provides the vacuum route between the vacuum
reservoir and SAI vacuum solenoid valve. A further small bore vacuum hose with a larger size elbow connector is
used to connect the SAI vacuum solenoid valve to the SAI control valves on each side of the engine via an
intermediate connection. The SAI vacuum solenoid valve port to the SAI control valves is located at a right angle to
the port to the vacuum reservoir.
The intermediate connection in the vacuum supply line is used to split the vacuum equally between the two SAI control
valves. The vacuum hose intermediate connection is located midpoint in front of the inlet manifold. All vacuum hose
lines are protected by flexible plastic sleeving.
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.
M17 0211
1
4
2
3
5
6

EMISSION CONTROL - V8
17-2-30 DESCRIPTION AND OPERATION
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/T4:
NOTE: Refer to 'SAI System Fault Finding' and 'Checking Malfunctions on SAI System' at the end of this section to
determine root cause of fault codes.
As a result of the SAI vacuum solenoid malfunction, other fault codes may also be stored in the ECM diagnostic
memory. These may include the following:
NOTE: A malfunction of the valve is logically expected to result in both engine banks reporting the same fault.
NOTE: Refer to 'SAI System Fault Finding' and 'Checking Malfunctions on SAI System' at the end of this section to
determine root cause of fault codes.
P-code Description
P0412SAI vacuum solenoid valve powerstage fault - harness damage, short circuit to
battery supply voltage
P0413SAI vacuum solenoid valve not connected, open circuit
P0414SAI vacuum solenoid valve short circuit to ground
P-code Description
P1412Secondary Air Injection System – Malfunction Bank 1 LH (Insufficient SAI flow
during passive test)
P1413Secondary Air Injection System – Air control valve always open Bank 1 LH
(Excessive SAI flow during active leak test)
P1414Secondary Air Injection System – Malfunction Bank 1 LH (Insufficient SAI flow
during passive test)
P1415Secondary Air Injection System – Malfunction Bank 2 RH (Insufficient SAI flow
during passive test)
P1416Secondary Air Injection System – Ait control valve always open Bank 2 RH
(Excessive SAI flow during active leak test)
P1417Secondary Air Injection System – Low air flow Bank 2 RH (Insufficient SAI flow
during active test)

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-31
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
The SAI control valves are located on brackets at each side of the engine.
The air injection supply pipes connect to a large bore port on the side of each SAI control valve via a short rubber
connection hose. A small bore vacuum port is located on each SAI control valve at the opposite side to the air injection
supply port. The vacuum supply to each vacuum operated SAI control valve is through small bore nylon hoses from
the SAI vacuum solenoid valve. An intermediate connector is included in the vacuum supply line to split the vacuum
applied to each vacuum operated valve, so that both valves open and close simultaneously.
When a vacuum is applied to the SAI control valves, the valve opens to allow the pressurised air from the SAI pump
through to the exhaust manifolds. The injection air is output from each SAI control valve through a port in the bottom
of each unit. A metal pipe connects between the output port of each SAI control valve and each exhaust manifold via
an intermediate T-piece. The T-piece splits the pressurised air delivered to ports at the outer side of the two centre
exhaust ports on each cylinder head. The pipes between the T-piece and the exhaust manifold are enclosed in
thermal sleeving to protect the surrounding components from the very high heat of the exhaust gas, particularly at
high engine speeds and loads.
When the SAI vacuum solenoid valve is de-energised, the vacuum supply line opens to atmosphere, this causes the
vacuum operated valves to close automatically and completely to prevent further air injection.
As a result of SAI control valve malfunction, certain fault codes may be stored in the ECM diagnostic memory, which
can be retrieved using Testbook/T4. These may include the following::
M17 0205
1
3
4
4
2
6
5

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-33
Vacuum Reservoir
1Vacuum port to SAI vacuum solenoid valve
2Vacuum port to intake manifold
(one-way valve end)3Vacuum reservoir
A vacuum reservoir is included in the vacuum supply line between the intake manifold and the SAI vacuum solenoid
valve. The vacuum reservoir contains a one-way valve, to stop depression leaking back towards the intake manifold
side. The reservoir holds a constant vacuum so that the SAI control valves open instantaneously as soon as the SAI
solenoid valve is energised.
The vacuum reservoir is a plastic canister construction located on a bracket at the LH side of the engine compartment
on vehicles up to 2003 model year and on the RH side of the engine compartment, near the bulkhead, on vehicles
from 2003 model year. It is important to ensure the reservoir is fitted in the correct orientation, and the correct vacuum
hoses are attached to their corresponding ports. The one-way valve end of the vacuum reservoir (cap end, to inlet
manifold) is fitted towards the rear of the vehicle.
A small bore nylon hose is used to connect the one-way valve end of the vacuum reservoir to a port on the RH side
of the inlet manifold. A further hose connects between the other port on the vacuum reservoir and a port on the front
of the SAI vacuum solenoid valve.
M17 0212
1
2
3

EMISSION CONTROL - V8
17-2-34 DESCRIPTION AND OPERATION
Crankcase Emission Control Operation
Oil laden noxious gas in the engine crankcase is drawn through a spiral oil separator 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 mass of fresh air which is drawn in from the
atmospheric side of the throttle butterfly to mix with the returned crankcase gas depends on the throttle position and
the engine speed.
1Hose – RH rocker cover to inlet manifold
2Inlet manifold
3Throttle body
4Air intake
5Hose – LH rocker cover to inlet manifold
6LH rocker cover breather tube
(without oil separator)7LH rocker cover baffle
8RH rocker cover baffle
9RH rocker cover breather tube
10Oil separator (integral with breather tube)
When the engine is running in cruise conditions or at idle, manifold pressure is low and the majority of gases are drawn
into the inlet manifold through the oil / vapour separator in the RH rocker cover stub pipe. At the same time, filtered
air is drawn from the throttle body into the engine via the LH rocker cover.
During periods of driving at Wide Open Throttle (WOT), pressure at either side of the throttle disc equalizes (manifold
depression collapses). The larger ventilation opening at the throttle housing positioned in the fast moving stream of
intake air, now offers more 'pull' than the small opening in the RH rocker cover and the flow of ventilation reverses,
drawing gases from the LH rocker cover into the throttle body for subsequent burning in the combustion chambers.

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-35
Exhaust Emission Control Operation
The oxygen content of the exhaust gas is monitored by heated oxygen sensors using either a four sensor (NAS only)
or two sensor setup, dependent on market destination and legislative requirements. Signals from the heated oxygen
sensors are input to the engine management ECM which correspond to the level of oxygen detected in the exhaust
gas. From ECM analysis of the data, necessary changes to the air:fuel mixture and ignition timing can be made to
bring the emission levels back within acceptable limits under all operating conditions.
Changes to the air:fuel ratio are needed when the engine is operating under particular conditions such as cold starting,
idle, cruise, full throttle or altitude. In order to maintain an optimum air:fuel ratio for differing conditions, the engine
management control system uses sensors to determine data which enable it to select the ideal ratio by increasing or
decreasing the air to fuel ratio. Improved fuel economy can be arranged by increasing the quantity of air to fuel to
create a lean mixture during part-throttle conditions, however lean running conditions are not employed on closed loop
systems where the maximum is λ = 1. Improved performance can be established by supplying a higher proportion of
fuel to create a rich mixture during idle and full-throttle operation. Rich running at wide open throttle (WOT) for
performance and at high load conditions helps to keep the exhaust temperature down to protect the catalyst and
exhaust valves.
The voltage of the heated oxygen sensors at λ = 1 is between 450 and 500 mV. The voltage decreases to 100 to 500
mV if there is an increase in oxygen content (λ > 1) indicating a lean mixture. The voltage increases to 500 to 1000
mV if there is a decrease in oxygen content (λ < 1), signifying a rich mixture.
The heated oxygen sensor needs to operate at high temperatures in order to function correctly (≥ 350° C). To achieve
this the sensors are fitted with heater elements which are controlled by a pulse width modulated (PWM) signal from
the engine management ECM. The heater element warms the sensor's ceramic layer from the inside so that the
sensor is hot enough for operation. The heater elements are supplied with current immediately following engine start
and are ready for closed loop control within about 20 to 30 seconds (longer at cold ambient temperatures less than
0°C (32°F)). Heating is also necessary during low load conditions when the temperature of the exhaust gases is
insufficient to maintain the required sensor temperatures. The maximum tip temperature is 930° C.
A non-functioning heater element will delay the sensor's readiness for closed loop control and influences emissions.
A diagnostic routine is utilised to measure both sensor heater current and the heater supply voltage so its resistance
can be calculated. The function is active once per drive cycle, as long as the heater has been switched on for a pre-
defined period and the current has stabilised. The PWM duty cycle is carefully controlled to prevent thermal shock to
cold sensors.
The heated oxygen sensors age with mileage, causing an increase in the response time to switch from rich to lean
and lean to rich. This increase in response time influences the closed loop control and leads to progressively
increased emissions. The response time of the pre-catalytic converter sensors are monitored by measuring the period
of rich to lean and lean to rich switching. The ECM monitors the switching time, and if the threshold period is exceeded
(200 milliseconds), the fault will be detected and stored in the ECM as a fault code (the MIL light will be illuminated
on NAS vehicles). NAS vehicle engine calibration uses downstream sensors to compensate for aged upstream
sensors, thereby maintaining low emissions.
Diagnosis of electrical faults is continuously monitored for both the pre-catalytic converter sensors and the post-
catalytic converter sensors (NAS only). This is achieved by checking the signal against maximum and minimum
threshold for open and short circuit conditions. For NAS vehicles, should the pre- and post-catalytic converters be
inadvertently transposed, the lambda signals will go to maximum but opposite extremes and the system will
automatically revert to open loop fuelling. The additional sensors for NAS vehicles provide mandatory monitoring of
the catalyst conversion efficiency and long term fuelling adaptations.
Note that some markets do not legislate for closed loop fuelling control and in this instance no heated oxygen
sensors will be fitted to the exhaust system.