1999 LAND ROVER DISCOVERY relay

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
17-2-42 DESCRIPTION AND OPERATION
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 Operation (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/T4.

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-43
Secondary Air Injection System
Operation
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.

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-45
Flow Test (P Codes P1414 and P1417)
When the Leak test has been passed successfully, the SAI control valves are then opened while the SAI pump is still
operational. Flow should now begin to enter the exhaust system. By monitoring the HO2S sensor voltage output, the
ECM determines if sufficient flow is being introduced into the exhaust system. Depending on which bank of the engine
detects the fault, one or both P codes can be stored.
Fault Finding Methodology
Malfunctions can be broadly categorised into two different categories: Flow Faults or Leak Faults.
Additionally, they also differ depending if the corresponding P code exists for both cylinder banks simultaneously or
is unique to one bank, for example:
Faults of each of the four basic types should be investigated in a different priority order, starting with the most logically
plausible cause or component.
Fault Finding Flow Charts
The following flow charts show the order of investigation that should be performed depending on the type of fault
present. These should be treated as guidelines to ensure that the most likely and plausible causes are addressed first.
However, the flow charts assume that no clear or obvious reason for failure exists. If the cause of the malfunction is
immediately obvious, then the flow charts should not be followed.
Once a malfunction is identified, it should be rectified as necessary and the system checked as per the instructions
in the following 'Checking Malfunctions' section.
NOTE: It is not necessary to follow the remainder of the flow chart once a potential root cause has been identified.
Flow Fault Finding chart
1Fault codes P1412, P1414, P1415 or P1417 present
2Insufficient flow detected
3Is fault present on both cylinder banks?
If 'NO' proceed to step 4
If 'YES' proceed to step 8
4Vacuum supply – Check for: blockage and/or vacuum line disconnected from SAI valve
5SAI Valve – Check for: jam / diaphragm leak or blockage
6Delivery Hoses to SAI Valve – Check for: blockage / leaks
7SAI Pipes to Cylinder Head – Check for: blockage / leaks
8Electrical Issue – Check for: Related P code (relay/fuse/solenoid), rectify as necessary and check connectors
9Vacuum Supply – Check for: Blocked/leaking vacuum lines or correct solenoid operation (open/closed)
10Delivery Hoses – Check for: Blocked/leaking hoses
11SAI Pump – Check for: Correct operation using TestBook/T4 or pump blockage/failure
12SAI Valves – Check for: Both SAI Valves jammed/blocked/leaking diaphragms
Leak Fault Finding Chart
1Fault codes P1413 or P1416 present
2SAI system leak detected
3Is fault present on both cylinder banks?
If 'NO' proceed to step 4
If 'YES' proceed to step 5
4SAI Valve – Check for: leakage
5Vacuum supply – Check for: solenoid stuck open (mechanical failure) or stuck open (electrical failure)
6SAI Valve – Check for: leakage from one or both valves
P Code Type One Bank Only Both Banks
FlowIII
LeakIII IV

EMISSION CONTROL - V8
DESCRIPTION AND OPERATION 17-2-47
The following table shows the components itemised on the above illustration and the test applicable to each
component.
Test 1– Secondary Air Injection (SAI) Pump
Power Supply and Relay
Check all wiring and connections.
Functional Check of SAI Pump
The ECM checks the engine coolant temperature when the engine is started in addition to checking the elapsed time
since the last engine start. The engine coolant temperature must be below 55°C (131°F) and the ambient temperature
above 8°C (46°F) for the SAI pump to run. Also, depending on the long term 'modelled' ambient temperature
determined by the ECM, the minimum time elapsed required since the last engine start can be up to 8.25 hours. The
period of time that the SAI pump runs for depends on the starting temperature of the engine and varies from
approximately 95 seconds for a start at 8°C (46°F) to 30 seconds for a start at 55°C (131°F).
With a warm engine which is switched off and the SAI pump relay removed, the SAI pump can be supplied with power
by bridging terminals 87 and 30 at the relay socket.
CAUTION: Ensure that terminals 87 and 87a are not connected or bridged in any way, a short circuit will
occur.
NOTE: TestBook/T4 can also be used to force the SAI system to perform an SAI active diagnostic routine. During this
routine the SAI pump will run for approximately 10 seconds.
When the terminals are bridged or the diagnostic routine initiated, the pump must run when requested which will be
noticeable by the running noise of the pump. Only allow the SAI pump to run for a maximum of 90 seconds and allow
sufficient time for the pump to cool down before running again.
If the SAI pump does not run or makes a scraping noise, it must be replaced. In this case, all other system components
must also be checked.
Noise Complaints
If the SAI pump runs but the operating noise is excessively loud, the external components of the pump, cable, hose
line, and decoupling segments, must be checked. Check the decoupling segments and hose line for distortion and
the cable and hose line for contact with the pump body.
If excessive noise still occurs, the SAI pump must be replaced.
NOTE: Before a new SAI pump is fitted, the SAI control valves must checked for correct function and tightness – Refer
to Test 2 – Secondary Air Injection (SAI) Control Valves.
When fitting a new SAI pump, ensure that the hose lines, the cable and the decoupling segments are fitted without
tension and contact with the pump body.
Item No. Component Description Applicable Test
1 SAI Pump Test 1 – Secondary Air Injection (SAI) Pump
2 SAI control valves (1 per engine bank) Test 2 – Secondary Air Injection (SAI) Control
Valves
3 Vacuum solenoid valve Test 3 – Vacuum Solenoid Valve
4 Delivery hoses to SAI control valves Test 4 – Delivery Hoses to Secondary air
Injection (SAI) Control Valves
5 Connection to air manifold (SAI rail) Test 5 – Connection to Air Manifold
6 Vacuum line (intake manifold to vacuum solenoid valve) Test 6 – Vacuum Lines
7 Vacuum lines (vacuum solenoid valve to SAI control valves) Test 6 – Vacuum Lines

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-3
1Mass air flow/ inlet air temperature sensor
2Fuel injectors
3High tension leads/spark plugs
4Fuel pump relay
5ATC compressor clutch relay/ cooling fan relay
6Throttle position sensor
7Heated oxygen sensor
8Idle air control valve
9Ignition coils
10Engine coolant temperature sensor
11Crankshaft speed and position sensor
12Knock sensor
13Camshaft position sensor

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-5
1Engine control module
2Crankshaft speed and position sensor
3Camshaft position sensor
4Engine coolant temperature sensor
5Mass air flow/ inlet air temperature sensor
6Throttle position sensor
7Heated oxygen sensors
8Fuel injectors
9Idle air control valve
10Fuel pump relay
11EVAP canister
12EVAP canister vent valve
13EVAP canister purge valve
14Fuel tank pressure sensor15Ignition coils
16Knock sensor
17Spark plugs
18High/ Low ratio switch
19Malfunction indication lamp
20Diagnostic connector
21Air temperature control clutch relay
22Air temperature control cooling fan relay
23ATC ECU
24CAN link to EAT
25SLABS ECU
26BCU
27Instrument cluster
28Thermostat monitoring sensor (where fitted)