1999 LAND ROVER DISCOVERY lock

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 17-2-45
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 17-2-49
Test 3 – Vacuum Solenoid Valve
Function
The vacuum solenoid valve is energised for the duration of the secondary air injection. The valve is open when
energised, the intake manifold vacuum acts on the diaphragm of the SAI control valve and the control valve opens.
The solenoid valve is closed when de-energised.
Power Supply
Remove the harness connector from the vacuum solenoid valve and check the voltage between the connection
terminals. No voltage must be present at the connector after switching off the SAI pump.
Opening/Tightness
Disconnect the vacuum line at one of the SAI control valves and connect a hand vacuum pump to the line. With the
engine running at idle, a pressure difference of a minimum of 390 mbar (5.65 lbf/in
2) must measurable on the hand
vacuum pump gauge with the vacuum solenoid valve energised.
The vacuum solenoid valve must be sealed when de-energised. If the Opening/tightness test fails, replace the
vacuum solenoid valv.
Test 4 – Delivery Hoses to Secondary air Injection (SAI) Control Valves
Visually inspect the delivery hoses to the SAI control valves for damage or blockage. If damage, condensate or
deposits are found the delivery hoses must be replaced. Check the hoses for correct connection and leaks.
Test 5 – Connection to Air Manifold
Check the connection for leaks visually or by using a leak detection spray. Reseal the connection if necessary.
Test 6 – Vacuum Lines
Visually inspect the vacuum lines for damage. Check each line for leaks or blockages using the vacuum hand pump.
Check the lines for correct connection.

ENGINE MANAGEMENT SYSTEM - V8
18-2-4 DESCRIPTION AND OPERATION
Engine management block diagram

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-7
The ECM controls the following outputs:
lFuel injectors (1 per cylinder).
lIgnition coils/ high tension leads/ spark plugs.
lFuel pump relay.
lIdle air control valve.
lHeated oxygen sensors.
lEVAP canister purge valve.
lEVAP canister vent solenoid (CVS) valve (where fitted).
lMalfunction Indicator Lamp (MIL)/ service engine soon lamp (where fitted).
lHill descent control (via SLABS interface).
lEVAP system fuel leak detection pump (where fitted)
lSecondary air injection pump (where fitted)
The ECM also interfaces with the following:
lDiagnostics via diagnostic connector with TestBook.
lController Area Network (CAN) link to EAT ECU.
lAir conditioning system.
lSelf Levelling & Anti-lock Braking System (SLABS) ECU.
lImmobilisation system via the body control unit (BCU).
lInstrument cluster.
lCruise control ECU
lActive Cornering Enhancement (ACE) ECU

ENGINE MANAGEMENT SYSTEM - V8
18-2-28 DESCRIPTION AND OPERATION
Throttle Position (TP) sensor (C0175)
The TP sensor is located on the throttle body assembly in the engine compartment. The ECM is able to determine the
position of the throttle plate and the rate of change of its angle. The ECM processes the signal received from the TP
sensor.
The TP sensor consists of a resistance track and a sliding contact connected to the throttle plate assembly. As the
throttle is opened and closed the sliding contact moves along the resistance track to change the output voltage of the
sensor. The ECM determines throttle plate position by processing this output voltage. The connection of the sensor
to the throttle plate assembly is via a shaft.
The ECM is able to determine the closed throttle position, this enables the TP sensor to be fitted without the need for
prior adjustment. The TP sensor signal has input into the ECM's fuelling strategy and also to determine closed throttle
position for idle speed control. The TP sensor also supplies the ECM with information to enable the overrun fuel cut
off strategy to be implemented. When the ECM receives closed throttle information from the TP sensor it closes the
injectors for the duration of the closed throttle time.
The TP sensor signal is also used by the Electronic Automatic Transmission (EAT) ECU to determine the correct point
for gear shifts and acceleration kickdown. The ECM also supplies the SLABS ECU with this TP sensor information as
a PWM signal.
Input/Output
The TP sensor has electrical input and output. Input is a 5 volt supply via pin 10 of connector C0636 of the ECM. The
signal output is via pin 24 of connector C0636 and is a varying voltage, less than 0.5V (closed throttle) and greater
than 4.5V (wide open throttle) depending on throttle plate position. The TP sensor earth is via pin 25 of connector
C0636 of the ECM, this acts as a screen to protect the integrity of the TP sensor signal.
The connector and sensor terminals are gold plated for corrosion and temperature resistance, care must be exercised
while probing the connector and sensor terminals.
If the TP sensor signal fails, the ECM uses a default value derived from engine load and speed.
The TP sensor can fail the following ways or supply incorrect signal:
lSensor open circuit.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lSignal out of parameters.
lBlocked air filter (load monitoring, ratio of the TP sensor to air flow).
lRestriction in air inlet (load monitoring, ratio of the TP sensor to air flow).
lVacuum leak

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-33
Fuel injectors
The fuel injectors are located beneath the air inlet manifold. They utilise an electrical solenoid to lift the injector needle
off its seat to allow fuel injection to take place. The fuel injectors provide excellent fuel atomisation in the lower portion
of the inlet manifold, the air/fuel mixture can then be drawn into the cylinders to give good combustion characteristics
and therefore excellent driveability.
There are eight fuel injectors one per cylinder that the ECM operates sequentially. All the injectors are fed from a
common fuel rail as part of the returnless fuel system. Fuel pressure is maintained at a constant 3.5 bar (52 lbf.in
2) by
a regulator that is integral with the fuel pump.

+ FUEL DELIVERY SYSTEM - V8, DESCRIPTION AND OPERATION, Description.
Input/Output
All eight fuel injectors are supplied with battery voltage via fuse number 1 located in engine compartment fuse box.
The ECM controls the individual earth path for each injector via its own pin at connector C0636 of the ECM multiplug.
This facility allows the ECM to control the fuel injectors so that sequential fuel injection can take place.
Typical hot engine injector pulse width values:
lIdle = 2.5 ms.
lPeak torque (3000 rev/min) = 7 ms The ECM controls injector earth as follows:
lCylinder No 1 - pin 41 of connector C0636 of the ECM multiplug.
lCylinder No 2 - pin 1 of connector C0636 of the ECM multiplug.
lCylinder No 3 - pin 27 of connector C0636 of the ECM multiplug.
lCylinder No 4 - pin 40 of connector C0636 of the ECM multiplug.
lCylinder No 5 - pin 2 of connector C0636 of the ECM multiplug.
lCylinder No 6 - pin 15 of connector C0636 of the ECM multiplug.
lCylinder No 7 - pin 14 of connector C0636 of the ECM multiplug.
lCylinder No 8 - pin 28 of connector C0636 of the ECM multiplug.
Individual injectors can be measured for resistance using a multimeter. An acceptable injector resistance is as follows:
l14.5 ± 0.7 ohms at 20 °C (68 °F).
The fuel injectors can fail in the following ways or supply incorrect signal:
lInjector actuator open circuit.
lShort circuit to vehicle supply.
lShort circuit to vehicle earth.
lBlocked injector.
lRestricted injector.
lLow fuel pressure.

ENGINE MANAGEMENT SYSTEM - V8
18-2-36 DESCRIPTION AND OPERATION
Idle Air Control Valve (IACV) (C0641)
The IACV is located on the side of the air inlet pipe on top of the engine. The IACV is used to maintain good quality
idle speed under all operating conditions.
When an engine is running at idle it is subject to a combination of internal and external loads that can affect idle speed.
These loads include engine friction, water pump, alternator operation, and air conditioning.
The IACV acts as an air bypass valve. The ECM uses the IACV to enable the closed loop idle speed calculation to be
made by the ECM. This calculation regulates the amount of air flow into the engine at idle, therefore compensating
for any internal or external loads that may affect idle speed.
The IACV utilises two coils that use opposing PWM signals to control the position of opening/closing of a rotary valve.
If one of the circuits that supply the PWM signal fails, the ECM closes down the remaining signal preventing the IACV
from working at its maximum/ minimum setting. If this should occur, the IACV automatically resumes a default idle
position. In this condition, the engine idle speed is raised and maintained at 1200 rev/min with no load placed on the
engine.
The idle speed in cold start condition is held at 1200 rev/min in neutral for 20 seconds and ignition timing is retarded
as a catalyst heating strategy. The cold start idle speed and the default idle position give the same engine speed 1200
rev/min, and although they are the same figure they must not be confused with each other as they are set separately
by the ECM.
Note that the rotary valve must not be forced to move by mechanical means. The actuator can not be
serviced; if defective, the entire IACV must be replaced.
Input/Output
The input to the IACV is a 12 volt signal from fuse 2 located in the engine compartment fuse box. The output earth
signal to open and close the actuator is controlled by the ECM as follows:
lIACV (open signal) - via pin 42 of connector C0636 of the ECM
lIACV (closed signal) - via pin 43 of connector C0636 of the ECM
The IACV can fail the following ways or supply incorrect signal:
lActuator faulty.
lRotary valve seized.
lWiring loom fault.
lConnector fault.
lIntake system air leak.
lBlocked actuator port or hoses.
lRestricted or crimped actuator port or hoses.
In the event of an IACV signal failure any of the following symptoms may be observed:
lEither low or high idle speed.
lEngine stalls.
lDifficult starting.
lIdle speed in default condition.