air condition LAND ROVER DISCOVERY 1999 Service Manual

EMISSION CONTROL - V8
17-2-44 DESCRIPTION AND OPERATION
SAI System Fault Finding and Check
Malfunctions
The SAI system diagnostics monitor the whole SAI system for correct operation. Malfunction of any one of the SAI
system components can cause fault codes to be stored in the ECM diagnostic memory.
Correct fault finding methods and investigation are essential to determine the root cause of the generated fault code(s)
and prevent mis-diagnosis.
NOTE: TestBook/T4 must be used to perform active SAI diagnostics.
Fault Finding
In the event of SAI system malfunction and P Codes 1412 – 1417 being stored in the ECM diagnostic memory, the
following information is designed to provide a logical checking process for investigation of the root cause(s) of the
fault. This fault finding guide should be used in conjunction with the following 'Checking Malfunctions' procedure and
other information contained in this Emissions section.
It is important that these procedures are performed to prevent the following:
lExcessive instances of No Fault Found (NFF) components in warranty returns
lMultiple repeat complaints from the customer before the cause of the fault is found.
The following table lists the P codes applicable to the SAI system and their meaning:
Passive Test (P Codes 1412 and 1415)
During normal SAI operation the ECM uses HO2S sensor voltage output to determine if sufficient flow is being
introduced into the exhaust system. Depending on which banks of the engine detect the fault, one or both P codes
can be stored.
Active Tests
If the normal operation of the passive SAI diagnostics cannot be completed, (SAI operation being suspended by load/
speed conditions, for instance) the ECM will attempt to perform an 'Active' test of the system when conditions allow.
These conditions include, but are not limited to: 'Engine fully warm' and 'Engine at idle'. The active test comprises two
parts; a 'Leak Test' followed by a 'Flow Test'.
Leak Test (P Codes P1413 and P1416)
The SAI pump is operated without opening the SAI control valves. In this condition no SAI flow should enter the
exhaust system. By monitoring the HO2S sensor voltage output, the ECM determines if the system is functioning
correctly. Depending on which bank of the engine detects the fault, one or both P codes can be stored.
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)

ENGINE MANAGEMENT SYSTEM - V8
18-2-6 DESCRIPTION AND OPERATION
Description - engine management
General
The V8 engine is equipped with the Bosch Motronic M5.2.1 engine management system. This system is a sequential
multiport fuel injection system controlled by an Engine Control Module (ECM).
A single ECM is used for the control of the existing 4.0 litre engine and the new 4.6 litre engine introduced with 03
model year vehicles for the NAS market only. The ECM contains the tunes for both engines variants. When the ECM
is replaced, TestBook/T4 must be used to select the correct tune to match the engine fitment.
The ECM has On Board Diagnostic (OBD) strategies as required by various market legislative bodies. To meet these
requirements the system monitors and reports on any faults that cause excessive exhaust emissions.
In markets that mandate OBD, the ECM monitors performance of the engine for misfires, catalyst efficiency, exhaust
leaks and evaporative control loss. If a fault occurs, the ECM stores the relevant fault code and warns the driver of
component failure by illuminating the Malfunction Indicator Light in the instrument pack.
In markets where OBD is not mandatory, the ECM will still monitor performance of the engine and store the fault code,
but will not illuminate the Malfunction Indicator Light.
The ECM uses input and output information from its sensors and actuators to control the following engine conditions:
lFuel quantity.
lClosed loop fuelling.
lOpen loop fuelling.
lIgnition timing.
lKnock control.
lIdle speed control.
lEmission control.
lOn-Board Diagnostic (OBD) where applicable.
lVehicle immobilisation.
lMisfire detection (where applicable).
lVehicle speed signal.
lRough road signal (where applicable).
lLow fuel level signal (where applicable).
lCoolant temperature gauge signal.
The ECM processes sensor information from the following input sources:
lIgnition switch (position II).
lCrankshaft speed and position sensor.
lCamshaft position sensor.
lEngine coolant temperature sensor.
lMass air flow sensor.
lIntake air temperature sensor.
lKnock sensor.
lThrottle position sensor.
lHeated oxygen sensors.
lHigh/ Low ratio switch.
lFuel tank pressure sensor (where fitted)
lThermostat monitoring sensor (where fitted)

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
18-2-18 DESCRIPTION AND OPERATION
Engine Coolant Temperature (ECT) sensor (C0196)
The ECT sensor is located at the front of the engine adjacent to the coolant outlet pipe. The ECT sensor forms a vital
part of the ECM operating strategy, and therefore the optimum control of the running of the engine. Richer air/ fuel
ratio is required at lower coolant temperatures such as cold starting. Coolant temperature information from the ECT
sensor is also vital to enable the ECM to weaken the air/ fuel mixture as temperature rises to maintain low emissions
and optimum performance.
For NAS vehicles with secondary air injection, the signal from the ECT sensor is monitored at engine start, to
determine whether the conditions are cold enough to warrant secondary air injection to be employed. The ECT sensor
is then monitored to switch off the secondary air injection when the required engine coolant temperature has been
attained.

+ EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Secondary Air Injection System.
The ECT works as a Negative Temperature Coefficient (NTC) sensor. As temperature rises, the resistance in the
sensor decreases, as temperature decreases, the resistance in the sensor increases. The ECT sensor forms part of
a voltage divider chain with a pull up resistor within the ECM. Consequently as the ECT sensor resistance changes,
the analogue voltage at the input signal from the ECT sensor to the ECM will be adjusted which corresponds to the
temperature of the engine coolant. With this information, the ECM can implement the correct strategies for cold start,
warm up etc. The ECM supplies the instrument cluster with a pulse width modulated (PWM) coolant temperature
signal to drive the temperature gauge.

ENGINE MANAGEMENT SYSTEM - V8
18-2-22 DESCRIPTION AND OPERATION
Input/Output
The ECM provides the thermostat monitoring sensor with a 5 volt reference via pin 21 of connector C0635 of the ECM,
and an earth via pin 5 of connector C0635 of the ECM.
There are three types of thermostat monitoring sensor diagnostic checks:
lSensor signal is above maximum threshold. For the ECM to register this as a fault, and illuminate the MIL, the
temperature registered by the thermostat monitoring sensor must be above 140 °C (284 °F) for more than 1
second.
lSensor signal is below minimum threshold. For the ECM to register this as a fault, and illuminate the MIL, the
temperature registered by the thermostat monitoring sensor must be below -33 °C (-27 °F) for more than 1
second, while the inlet air temperature reading is greater than -32 °C (-25 °F).
lSignal difference between ECT sensor and thermostat monitoring sensor is below maximum threshold. For the
ECM to register this as a fault, and illuminate the MIL, the following conditions must exist:
lNo maximum or minimum threshold signal faults exist.
lNo faults are recorded against the thermostat monitoring sensor or vehicle speed signal.
lEngine not in idle speed control.
lFuel cut-off not active.
lEngine speed is greater than 400 rpm.
lRoad speed is greater than 0 mph.
lIntegrated mass air flow from engine start to fuel cut-off is greater than set value (between 3 kg and 10 kg
dependent upon engine coolant temperature at engine start).
lEngine coolant temperature at engine start is between 9 °C and 39 °C (48 °F and 102 °F).
lHigh range is selected.
lDelay time before thermostat monitoring is enabled is between set limits (between 50 and 500 seconds
dependent upon engine coolant temperature at engine start).
lEngine coolant temperature is greater than 90 °C (194 °F).
lThe difference between the ECT sensor reading and the thermostat monitoring sensor reading is less than
39 °C (102 °F).

ENGINE MANAGEMENT SYSTEM - V8
18-2-30 DESCRIPTION AND OPERATION
Heated Oxygen Sensors (HO2S) (C0642)
The market requirement dictates how many HO
2S are fitted to the vehicle.
l4 sensors are fitted to all NAS and EU-3 vehicles.
l2 sensors fitted to all UK, European, Australia and Japanese pre EU-3 specification vehicles.
lNo sensors fitted to ROW vehicles.
The HO
2S monitor the oxygen content of the exhaust gases. By positioning the sensors one for each bank upstream
of the catalytic converter in the exhaust pipe, the ECM can control fuelling on each bank independently of the other.
This allows greater control of the air:fuel ratio and maintains optimum catalyst efficiency. On NAS vehicles the ECM
also uses two HO
2S positioned downstream of the catalytic converters in the exhaust pipe to monitor catalytic
converter efficiency. The ECM is able to achieve this by comparing the values of the upstream HO
2S and the down
stream sensor for the same bank. These comparative values form part of the ECM OBD strategy.
The HO
2S uses zirconium contained in a galvanic cell surrounded by a gas permeable ceramic, this produces an
output voltage proportional to the ratio difference between the oxygen in the exhaust gases and to the ambient
oxygen.
The HO
2S operates at approximately 350 °C (662 °F). To achieve this temperature the HO2S incorporate a heating
element which is controlled by a PWM signal from the ECM. The elements are activated immediately after engine
starts and also under low engine load conditions when the exhaust gas temperature is insufficient to maintain the
required HO
2S temperature. If the heater fails, the ECM will not allow closed loop fuelling to be implemented until the
sensor has achieved the required temperature.
This value equates to an HO
2S output of 450 to 500 mV. A richer mixture can be shown as λ = 0.97, this pushes the
HO
2S output voltage towards 1000 mV. A leaner mixture can be shown as λ = 1.10, this pushes the HO2S output
voltage towards 100 mV.
From cold start, the ECM runs an open loop fuelling strategy. The ECM keeps this strategy in place until the HO
2S is
at a working temperature of 350 °C (662 °F). At this point the ECM starts to receive HO
2S information and it can then
switch into closed loop fuelling as part of its adaptive strategy. The maximum working temperature of the tip of the
HO
2S is 930 °C (1706 °F), temperatures above this will damage the sensor.
HO
2S age with use, this increases their response time to switch from rich to lean and from lean to rich. This can lead
to increased exhaust emissions over a period of time. The switching time of the upstream sensors are monitored by
the ECM. If a pre-determined threshold is exceeded, a failure is detected and the MIL illuminated.

+ EMISSION CONTROL - V8, DESCRIPTION AND OPERATION, Exhaust Emission Control System.
Input/Output
The upstream and downstream HO
2S are colour coded to prevent incorrect fitting. The tips of the upstream sensors
are physically different to the tips of the downstream sensors.
The HO
2S are colour coded as follows:
lUpstream sensors (both banks) - orange.
lDownstream sensors (both banks) - grey.
The four HO
2S have a direct battery supply to the heater via fuse 2 located in the engine compartment fuse box.

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.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-37
There are eight IACV diagnostic checks performed by the ECM:
lOutput short circuit to earth – opening coil
lOutput short circuit to battery supply – opening coil
lOutput open circuit – opening coil
lOutput short circuit to earth – closing coil
lOutput short circuit to battery voltage – closing coil
lOutput open circuit – closing coil
lBlocked IACV – rev/min error low (engine speed must be 100 rev/min less than the target speed, engine load
less than 2.5 and the measured air flow more than 10 kg/h less than the expected air flow for a fault condition to
be flagged).
lBlocked IACV – rev/min error high (the engine speed must be more than 180 rev/min greater than the target
speed and the measured air flow more than 10 kg/h greater than the expected air flow for a fault condition to be
flagged).
Should a malfunction of the component occur, the following fault codes may be evident and can be retrieved by
TestBook.
P Code J2012 Description Land Rover Description
P1510 IACV opening coil malfunction Short circuit to battery supply - opening winding
P1513 IACV opening coil malfunction Short circuit to earth - opening winding
P1514 IACV opening coil malfunction Open circuit - opening winding
P1553 IACV closing coil malfunction Short circuit to battery supply - closing winding
P1552 IACV closing coil malfunction Short circuit to earth - closing winding
P1551 IACV closing coil malfunction Open circuit - closing winding
P0505 Idle control system malfunction Blocked IACV - high or low rev/min error

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-45
Malfunction Indicator Lamp (MIL)/ service engine soon warning lamp
The MIL/ service engine soon warning lamp is located in the instrument cluster. It illuminates to alert the driver to
system malfunctions. Service engine soon warning lamp is the name for this warning lamp in NAS only, it is called
MIL in all other markets.
During ignition a self-test function of the lamp is carried out. The lamp will illuminate for 3 seconds then it will
extinguish if no faults exist.

+ INSTRUMENTS, DESCRIPTION AND OPERATION, Description.
Input/Output
The MIL is supplied with battery voltage from the instrument cluster. When the ECM detects a fault, it provides an
earth path to illuminate the MIL. Output to the MIL is via pin 20 of connector C0637 of the ECM.
Air Temperature Control (ATC) request
The ATC request comes via the ATC switch located in the facia panel. When the driver operates the switch it acts as
a request from the ATC ECU to engage the ATC clutch to drive the system.
During periods of high driver demand such as hard acceleration or maximum rev/min the ATC clutch will be disabled
for a short time. This is to reduce the load on the engine.

+ AIR CONDITIONING, DESCRIPTION AND OPERATION, Description.

ENGINE MANAGEMENT SYSTEM - V8
18-2-46 DESCRIPTION AND OPERATION
Input/Output
The operation of the ATC request is via a switch being connected to earth. Voltage is supplied via pin 38 of connector
C0637 of the ECM, at the point at when the switch is pressed the connection is made and the ATC clutch is engaged.
The ATC request can fail as follows:
lOpen circuit.
lShort circuit to voltage supply.
lShort circuit to vehicle earth.
lWiring loom fault.
In the event of an ATC request failure, the ATC system does not work.
Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by
TestBook.
P Code J2012 Description Land Rover Description
P1535 Air conditioning compressor request
malfunctionATC requested when not in standby mode