Range Rover. Manual — part 97
LAND ROVER V8
55
DESCRIPTION AND OPERATION
Diagnosis of electrical faults is continually monitored
by the ECM in both the upstream sensors and
downstream sensors (NAS only). The sensor signal is
checked against stored minimum and maximum
threshold values equating to short and open circuit
conditions.
If an HO
2
S sensor should fail, the following fault codes
will be generated by the ECM diagnostics, which can
be retrieved by Testbook:
•
P1129 - Front heated oxygen sensors
transposed
Upstream sensor LH bank - electrical (NAS only)
•
P0130 - Stoichiometric ratio outside operating
band
•
P0132 - Short circuit to battery supply
•
P0134 - Open circuit
Downstream sensor LH bank - electrical
•
P0136 - Stoichiometric ratio outside operating
band
•
P0137 - Short circuit to battery supply
•
P0138 - Short circuit to ground or chemical shift
down
•
P0140 - Open circuit
Upstream sensor RH bank - electrical (NAS only)
•
P0150 - Stoichiometric ratio outside operating
band
•
P0152 - Short circuit to battery supply
•
P0154 - Open circuit
Downstream sensor RH bank - electrical
•
P0156 - Stoichiometric ratio outside operating
band
•
P0157 - Short circuit to ground
•
P0158 - Short circuit to battery voltage
•
P0160 - Open circuit
Upstream sensors aged (NAS only)
•
P0133 - Upstream sensor aged - Period time too
short LH bank
•
P0133 - Upstream sensor aged - Period time too
long LH bank
•
P0153 - Upstream sensor aged - Period time too
short RH bank
•
P0153 - Upstream sensor aged - Period time too
long RH bank
•
P1170 - Upstream sensor aged - ATV adaption
too lean LH bank
•
P1170 - Upstream sensor aged - ATV adaption
too rich LH bank
•
P1173 - Upstream sensor aged - ATV adaption
too lean RH bank
•
P1173 - Upstream sensor aged - ATV adaption
too rich RH bank
Sensor Heater faults
•
P0135 - Upstream heater LH bank - Short circuit
(NAS only)
•
P0135 - Upstream heater LH bank - Open circuit
(NAS only)
•
P0141 - Downstream heater LH bank - Short
circuit
•
P0141 - Downstream heater LH bank - Open
circuit
•
P0155 - Upstream heater RH bank - Short circuit
(NAS only)
•
P0155 - Upstream heater RH bank - Open circuit
(NAS only)
•
P0161 - Downstream heater LH bank - Short
circuit
•
P0161 - Downstream heater LH bank - Open
circuit
19
FUEL SYSTEM
NEW RANGE ROVER
56
DESCRIPTION AND OPERATION
A diagnostic routine is used 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.
On NAS vehicles, the catalysts are monitored to
determine emission pollutant conversion efficiency;
the following fault codes will be generated by the ECM
diagnostics, which can be retrieved by Testbook:
•
P0420 - Catalyst efficiency deteriorated LH bank
•
P0430 - Catalyst efficiency deteriorated RH bank
See EMISSION CONTROL, Description and
operation.
Fuel pump relay - from 99MY
The fuel pump relay is fitted in the engine
compartment fusebox which is situated at the front
right hand side of the engine compartment. The relay
is a four-pin normally open type, encapsulated in a
yellow plastic housing.
The fuel supplied to the injectors from the in-tank fuel
pump is controlled by the ECM via the fuel pump
relay. During engine cranking, the fuel pump relay is
activated by the ECM allowing the fuel system to be
pressurised to 3.5 bar (52 lbf.in
2
). The pump relay is
then deactivated until engine start has been achieved.
Battery voltage is supplied via the engine
compartment fusebox and relay activation is achieved
by ground path switching through the ECM.
If the fuel pump relay should fail, the following
symptoms may be observed:
•
Engine stalls or will not start
•
No fuel pressure at the fuel injectors
A fuel pump relay failure is likely to occur for the
following reasons:
•
Relay drive open circuit
•
Short circuit to vehicle supply or ground
•
Component failure
If the fuel pump relay should fail, the following fault
codes will be generated by the ECM diagnostics,
which can be retrieved by Testbook:
•
P1230 - Fuel pump relay open circuit - not the
fuel pump itself
•
P1231 - Fuel pump relay short circuit to battery
supply - not the fuel pump itself
•
P1232 - Fuel pump relay short circuit to ground -
not the fuel pump itself
LAND ROVER V8
57
DESCRIPTION AND OPERATION
Advanced Evaporative Emissions System - from
99MY (NAS only)
The Bosch Motronic 5.2.1 ECM includes control for
the evaporative emissions system components, its
purpose is to minimise the evaporative loss of fuel
vapour from the fuel system to the atmosphere. This
is achieved by venting the system through an EVAP
canister filled with vapour absorbing charcoal. The
charcoal acts like a sponge and stores the vapour
until the canister is purged under the control of the
ECM.
Fuel vapour is stored in the activated charcoal
canister for retention when the vehicle is not
operating. When the vehicle is operating, fuel vapour
is drawn from the canister into the engine via a purge
control valve. The vapour is then delivered to the
intake plenum chamber to be supplied to the engine
cylinders where it is burned in the combustion
process.
See EMISSION CONTROL, Description and
operation.
Fuel Filling
During fuel filling, the fuel vapour displaced from the
fuel tank is allowed to escape to atmosphere; valves
within the fuel filler prevent any vapour escaping
through the EVAP canister as this can adversely
effect the fuel cut-off height. Only fuel vapour
generated whilst driving is prevented from escaping to
atmosphere by absorption into the EVAP canister.
The fuel filler shuts off to leave the tank approximately
10% empty to ensure the roll over valves (ROVs) are
always above the fuel level and so vapour can escape
to the EVAP canister and the tank can breathe. The
back pressures normally generated during fuel filling
are too low to open the pressure relief valve, but
vapour pressures accumulated during driving are
higher and can open the pressure relief valve. Should
the vehicle be overturned, the ROVs shut off to
prevent any fuel spillage.
Fuel Tank Venting
Fuel vapour generated from within the fuel tank as the
fuel heats up is stored in the tank until the pressure
exceeds the operating pressure of the two-way valve.
When the two-way valve opens, the fuel vapour
passes along the vent line from the fuel tank via the
fuel tank vapour separator to the evaporation inlet port
of the EVAP canister.
Liquid fuel must not be allowed to contaminate the
charcoal in the EVAP canister. To prevent this, the
fuel vapour separator fitted to the fuel filler neck
allows fuel to drain back into the tank. As the fuel
vapour cools, it condenses and is allowed to flow back
into the fuel tank from the vent line by way of the
two-way valve.
The EVAP canister contains charcoal pellets which
absorbs and stores the fuel vapour from the fuel tank
while the engine is not running. When the canister is
not being purged, the fuel vapour remains in the
canister and clean air exits the canister via the air inlet
port.
ECM Purge Control
The engine management ECM controls the output
signals to the purge valve and the canister vent
solenoid (CVS) valve, and receives an input from the
fuel tank pressure sensor. The system will not work
properly if there is a leakage or clogging within the
system, or if the purge valve cannot be controlled.
When the engine is running, the ECM decides when
conditions are correct for the vapour to be purged
from the canister and opens the canister purge valve.
This connects a manifold vacuum line to the canister
and fuel vapour containing the hydrocarbons is drawn
from the canister’s charcoal element to be burned in
the engine. Clean air is drawn into the canister
through the air inlet port to fill the displaced volume of
vapour.
The purge valve remains closed below preset coolant
and engine speed values to protect the engine tune
and catalytic converter performance. If the EVAP
canister was purged during cold running or at idling
speed the additional enrichment in the fuel mixture
would delay the catalytic converter light off time and
cause erratic idle. When the purge valve is opened,
fuel vapour from the EVAP canister is drawn into the
plenum chamber downside of the throttle housing, to
be delivered to the combustion chambers for burning.
19
FUEL SYSTEM
NEW RANGE ROVER
58
DESCRIPTION AND OPERATION
The purge valve is opened and closed in accordance
with a PWM signal supplied from the ECM. Possible
failure modes associated with the purge valve failure
are listed below:
•
Valve drive open circuit
•
Short circuit to vehicle supply or ground
•
Purge valve or pipework blocked or restricted
•
Purge valve stuck open
•
Pipework joints leaking or disconnected.
Possible symptoms associated with purge valve or
associated pipework failure is listed below:
•
Engine may stall on return to idle if purge valve
is stuck open
•
Poor idling quality if the purge valve is stuck
open
•
Fuelling adaptions forced excessively lean if the
EVAP canister is clear and the purge valve is
stuck open.
•
Fuelling adaptions forced excessively rich if the
EVAP canister is saturated and the purge valve
is stuck open.
•
Saturation of the EVAP canister if the purge
valve is stuck closed.
To maintain driveability and effective emission control,
purging control must be closely controlled by the
ECM, as a 1% concentration of fuel vapour from the
EVAP canister in the air intake may shift the air:fuel
ratio by as much as 20%. The ECM must purge the
fuel vapour from the EVAP canister at regular
intervals as its storage capacity is limited and an
excessive build-up of fuel pressure in the system
could increase the likelihood of vapour leaks. Canister
purging is cycled with the fuelling adaption as both
cannot be active at the same time. The ECM alters
the PWM signal to the purge valve to control the rate
of purging of the canister to maintain the optimum
stoichiometric air:fuel mixture for the engine.
See EMISSION CONTROL, Description and
operation.
Leak Test
The evaporative emission system used on NAS
vehicles includes a fuel pressure sensor and a
canister vent solenoid (CVS) valve. The system is
capable of detecting holes in the fuel system down to
1 mm (0.04 in.).
The test is carried out in three parts:
First the purge valve and the CVS valve closes off the
storage system and the vent pressure increases due
to the fuel vapour pressure level in the tank. If the
pressure level is greater than the acceptable limit, the
test will abort because a false leak test response will
result. In part two of the test, the purge valve is
opened (preferably with the engine idling) and the fuel
tank pressure will decrease due to purge operation. In
part three of the test, the leak measurement test is
performed. The pressure response of the tests
determines the level of the leak, and if greater than
the limit on two consecutive tests, the ECM stores the
fault in diagnostic memory and the MIL light on the
instrument pack is illuminated. The test is only carried
out at idle with the vehicle stationary. Following the
test, the system returns to normal purge operation
after the CVS valve opens. The in-tank pressure
sensor monitors the pressure build-up to determine
whether leaks are present.
Possible reasons for a test failure are listed below:
•
Fuel filler not tightened or cap missing
•
Sensor or actuator open circuit
•
Short circuit to vehicle supply or ground
•
Either purge or CVS valve stuck open
•
Either purge or CVS valve stuck closed or
blocked pipe
•
Piping broken or not connected
•
Loose 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 test, but by the engine management ECM
detecting that the fuelling adaption is suspended. The
evaluation of the leakage is dependent on the
differential pressure between the fuel tank and the
ambient atmospheric pressure. The diagnostic test is
disabled at altitudes above 2,800 metres (9,500 ft).
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