Range Rover. Manual — part 96
LAND ROVER V8
51
DESCRIPTION AND OPERATION
If an injector should fail, the following symptoms may
be observed:
•
Rough running
•
Difficult starting
•
Engine misfire
•
Possible catalyst damage
•
High emissions
•
Fuelling and idle speed control adaptations
disabled
A fuel injector failure is likely to occur for the following
reasons:
•
Actuator open circuit
•
Short circuit to vehicle 12V supply or ground
•
Blocked or restricted injector
•
Low fuel pressure
If a fuel injector should fail, the following fault codes
will be generated by the ECM diagnostics, which can
be retrieved by Testbook:
Injector 1
•
P0201 - Open circuit
•
P0261 - Short circuit to ground
•
P0262 - Short circuit to battery supply
Injector 2
•
P0202 - Open circuit
•
P0264 - Short circuit to ground
•
P0265 - Short circuit to battery supply
Injector 3
•
P0203 - Open circuit
•
P0267 - Short circuit to ground
•
P0268 - Short circuit to battery supply
Injector 4
•
P0204 - Open circuit
•
P0270 - Short circuit to ground
•
P0271 - Short circuit to battery supply
Injector 5
•
P0205 - Open circuit
•
P0273 - Short circuit to ground
•
P0274 - Short circuit to battery supply
Injector 6
•
P0206 - Open circuit
•
P0276 - Short circuit to ground
•
P0277 - Short circuit to battery supply
Injector 7
•
P0207 - Open circuit
•
P0279 - Short circuit to ground
•
P0280 - Short circuit to battery supply
Injector 8
•
P0208 - Open circuit
•
P0282 - Short circuit to ground
•
P0283 - Short circuit to battery supply
All injectors
•
P0170 - High leak rate detection
•
P0300 to P0308 - Misfire detected excess
emissions - blocked or restricted injector
•
P0300 to P0308 - Misfire detected catalyst
damage - blocked or restricted injector
Specific P-code number depends on which cylinder(s)
is experiencing the fault.
19
FUEL SYSTEM
NEW RANGE ROVER
52
DESCRIPTION AND OPERATION
Idle Air Control Valve (IACV) - from 99MY
The idle air control valve is positioned at the top rear
of the engine, on the side of the air inlet pipe. The unit
is clamped to the inlet manifold by two bolts passing
through ’P’ clips.
A grey three-pin connector is provided at the back of
the unit. One wire supplies the voltage feed from the
engine compartment fusebox, while the other two
wires carry the valve positioning control signals.
The IACV is used to make adjustments to optimise the
engine idle speed under all operating conditions.
Engine load at idle will vary in reaction to a
combination of conditions and influences such as
engine friction, water pump , air conditioning, altitude
etc. The IACV utilises closed loop control to
compensate for the changing conditions by regulating
the air flow into the engine.
The IACV utilises two electromagnetic coils which use
opposing PWM signals to control the positioning of a
rotary valve. The rotary valve position determines how
much air is allowed to flow through the bypass route.
CAUTION: Do not try to forcibly set the
valve position, the actuator cannot be
serviced. In the event of failure the IACV
must be replaced as a unit.
If one of the electrical circuits supplying the PWM
signals fails, the ECM switches off the other circuit to
prevent the valve from biasing towards a maximum or
minimum setting. Under these conditions, a default
position for the valve is provided by a permanent
magnet, which sets the valve position to maintain the
idle speed at a fixed value of approximately 1200 rpm
with no load applied.
During cold start conditions, the idle speed is held at
1200 rpm in neutral for 20 seconds. Ignition timing is
retarded as a catalyst heating strategy.
If the IACV should fail, the following symptoms may
be observed:
•
Either low or high idle speed
•
Engine stalls
•
Difficult starting
•
Raised idle speed in default condition.
An IACV failure is likely to occur for the following
reasons:
•
Rotary valve seized
•
Faulty actuator
•
Connector or harness fault
•
Intake system air leak
•
Actuator port or hoses blocked, restricted or
crimped
If the IACV should fail, the following fault codes will be
generated by the ECM diagnostics, which can be
retrieved by Testbook:
•
P0505 - Blocked IACV valve - rpm error high or
low
•
P1510 - Short circuit to battery supply - opening
winding
•
P1513 - Short circuit to ground - opening winding
•
P1514 - Open circuit - opening winding
•
P1553 - Short circuit to battery supply - closing
windings
•
P1552 - Short circuit to ground - closing winding
•
P1551 - Open circuit - closing winding
LAND ROVER V8
53
DESCRIPTION AND OPERATION
Heated Oxygen Sensors (HO
2
S) - from 99MY
1. RH catalytic converter
2. Heated oxygen sensors - post-catalytic converters (2 off - NAS only)
3. LH catalytic converter
4. Heated oxygen sensors - pre-catalytic converters (2 off)
The number of heated oxygen (HO
2
S) sensors fitted
to a vehicle is dependent on the particular market
requirements:
•
4 - HO
2
S sensors (NAS vehicles)
•
2 - HO
2
S (UK, European, Australia & Japan
vehicles)
•
0 - HO
2
S (Gulf & ROW vehicles)
The HO
2
S sensors monitor the level of oxygen in the
exhaust gases and the resulting data is used by the
ECM to control the air:fuel mixture to provide the most
efficient mix under all operating conditions. By
positioning a sensor in the stream of exhaust gases
from each bank of cylinders of the V8 engine enables
the ECM to control the fuelling on each bank
independently. This allows the ECM to provide more
accurate control of the air:fuel ratio and monitor
catalytic converter efficiency.
Two upstream sensors are utilised in markets where
closed loop fuelling is the only mandatory
requirement. For markets where closed loop fuelling
control is not mandatory, HO
2
S sensors are not
included.
NAS vehicles utilise four HO
2
S sensors, one upstream
of each catalyst and one downstream of each catalyst.
This arrangement is used to monitor catalytic
converter efficiency and so determine when a catalyst
is no longer working effectively. Obtaining catalytic
converter efficiency data is a mandatory requirement
of the ECM OBD strategy. The downstream sensors
also provide for long term fuelling adaptions.
The basic closed control loop comprises the engine
(controlled system), the heated oxygen sensors
(measuring elements) and the engine management
ECM (control) and the injectors and ignition
(actuators). Although 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 and full load.
From cold start the ECM runs an open loop strategy,
which is kept in place until the sensor’s working
temperature has been reached.
19
FUEL SYSTEM
NEW RANGE ROVER
54
DESCRIPTION AND OPERATION
The heated oxygen sensors age with mileage, which
will cause an increase in their response time for
switching from rich to lean and lean to rich. The
increase in response time influences the closed loop
control and leads to progressively increased
emissions. If the response rate is diagnosed to be
exceeding a preset threshold, an error code will be
stored in the ECM and the MIL warning lamp will be
illuminated (NAS only).
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
pre-catalytic sensors are identified by three slots in
the protective tube, whereas the post-catalytic
sensors have four square indentations and a hole in
the end of the protective tube (NAS only).
NOTE: The maximum working temperature
of the tip of the HO
2
S sensor is 930
°
C
(1706
°
F); temperatures higher than this
will damage the sensor.
The heater elements are controlled by a PWM signal
from the ECM. The heater elements are operated
immediately following engine start and also during low
load conditions when the temperature of the exhaust
gases is insufficient to maintain the required sensor
temperatures. The heater element warms the sensor’s
ceramic layer from the inside so that the sensor is hot
enough for operation. After start up, the sensors are
ready for closed loop control within about 20 to 30
seconds.
If the heater element fails, the ECM will not allow
closed loop fuelling to be implemented until the sensor
has achieved the required temperature. 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 pre-catalytic and post-catalytic converters are not
interchangeable, and although it is possible to mount
them in transposed positions, their harness
connections are of different gender and colour:
•
Upstream sensors have orange connectors.
•
Downstream sensors have grey connectors.
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 effect system performance with
time.
NOTE: Sensor voltage is most easily
monitored using "Testbook".
If a heated oxygen sensor should fail, the following
symptoms may be observed:
•
Default to open loop fuelling on the catalyst bank
with the failed sensor.
•
If sensor get crossed, the engine will run
normally after the initial start, but then become
progressively unstable. One bank will clamp at
the maximum rich level, and the other bank will
clamp at maximum lean. The system will then
revert to open loop fuelling.
•
High CO reading
•
Excess emissions
•
Strong smell of hydrogen sulphide (H
2
S) until the
ECM defaults to open loop fuelling
•
MIL lamp illuminated (NAS only)
A heated oxygen sensor failure is likely to occur for
the following reasons:
•
Damaged or incorrectly fitted sensor
•
Sensor open circuit or disconnected
•
Short circuit to vehicle supply or ground
•
Stoichiometric ratio outside the correct operating
band
•
Contamination from leaded fuel or other sources
•
Change in sensor characteristics - Chemical
Shift Down (CSD)
•
Sensors from LH and RH banks crossed
•
Air leak into exhaust system (cracked pipe / weld
or loose fixings)
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