fuel JAGUAR XF 2009 1.G AJ133 5.0L Engine Manual

Technical TrainingNP10-V8JLR: AJ133 5.0-Liter DFI V8 Engine04/14/20093-23
Engine Management SystemHeated Oxygen Sensors
Upstream Universal Heated Exhaust Gas Oxygen Sensors
In order to improve the control of the air : fuel ratio
(AFR) under varying engine conditions, a linear or ‘uni-
versal’ heated exhaust gas oxygen (UHEGO) sensor is
used in the upstream location. The UHEGO has a vary-
ing current response to changes in the exhaust gas oxy-
gen content.
The AFR can be maintained more precisely within a
range from approximately 12:1 to 18:1, not just stoichio-
metric. Voltage is maintained at approximately 450 mV
by applying a current.
The current required to maintain the constant voltage is
directly proportional to the AFR. A higher current indi-
cates a leaner condition; a lower current indicates a
richer condition. The current varies with the temperature
of the sensor and is therefore difficult to measure for
technician diagnostic purposes.
The upstream UHEGO sensors need to operate at high
temperatures – 750°C (1,382°F) – in order to function
correctly. To achieve this, the sensors are fitted with
heater elements that 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.A non-functioning heater delays the sensor’s readiness
for closed loop control and influences emissions. The
PWM duty cycle is carefully controlled to reduce ther-
mal shock risk to cold sensors.
The upstream UHEGO sensors are mounted to the
engine on the exhaust manifolds, in the mating flange to
the exhaust pipes. There is one sensor per bank. The sen-
sors are fitted during engine assembly.
Upstream UHEGO Output
NP10V8108
+10 mA
NOMINAL APPLIED CURRENT
-10 mA
AFR 12:1
APPLIED CURRENT(APPROXIMATE)
AFR 18:1λ = 1

3-2404/14/2009NP10-V8JLR: AJ133 5.0-Liter DFI V8 EngineTechnical Training
Heated Oxygen SensorsEngine Management System
Downstream Heated Oxygen Sensors
The latest switching downstream exhaust sensors are
precise-control heated oxygen sensors (HO2S). These
sensors have a tighter lean/rich tolerance compared to
previous HO2S. The only visible distinction between the
current and previous HO2S is the part number.
The downstream HO2S uses smaller elements in its con-
struction to enable quicker heat-up times to control fuel
metering at lower temperatures (emissions).
The primary function of the downstream HO2S is to
ensure correct operation of the three way catalyst.
The downstream HO2S uses Zirconium technology that
produces an output voltage dependant upon the ratio of
exhaust gas oxygen to the ambient oxygen. The device
contains a Galvanic cell surrounded by gas-permeable
ceramic, the voltage of which depends upon the level of
O2 diffusing through.
Nominal output voltage of the device for lambda = 1 is
300 – 500mV. As the fuel mixture becomes richer (<1)
the voltage tends towards 900mV and as it becomes
leaner (lambda > 1) the voltage tends towards 0 volts. The downstream HO2S are mounted in the exhaust sys-
tem part way in the rear of the catalyst.
Downstream HO2S Output
NP10V8115
V
λ = 1
4.5V

Technical TrainingNP10-V8JLR: AJ133 5.0-Liter DFI V8 Engine04/14/20093-25
Engine Management SystemHeated Oxygen Sensors
Safety Precautions
WARNINGS:
• Anti-seize compound used on service sensor threads may be a health hazard. Avoid skin
contact.
• Exhaust system components, catalysts in particular, operate at high temperatures and
remain hot for a long time after operation.
CAUTIONS:
• Oxygen sensors must be treated with the utmost care before and during the fitting
process. The sensors have ceramic material
within them that can easily crack if
dropped or over-torqued. They must be
tightened to the specified torque figure with
a calibrated torque wrench. Care should be
taken not to contaminate the sensor tip
when the anti-seize compound is used on
the thread.
• To prevent damage to the sensors, a special tool (box spanner) should be used when
removing.
• If the sensor sticks in the exhaust, apply de- seize product and use a repeating tighten
and loosen strategy.
• Ensure that the sensor harness is robustly secured away from moving or hot parts. Failure Modes
• Mechanical fitting and integrity of the sensor (i.e.
cracked)
• Sensor open circuit/disconnected
• Short circuit to battery voltage or ground.
• Lambda ratio outside operating band
• Crossed sensors (RH bank fitted to LH bank and vice-versa)
• Contamination from leaded fuel or other sources
• Harness damage
• Air leak into exhaust system (cracked pipe/weld or loose fixings)
Failure Symptoms
• Default to open loop fuel metering
• High CO reading
• Strong smell of sulfur (rotten eggs) until default condition
• Excess emissions
• Unstable operation
• Reduced performance

3-2804/14/2009NP10-V8JLR: AJ133 5.0-Liter DFI V8 EngineTechnical Training
Fuel Tank Canister Purge ValveEngine Management System
FUEL TANK CANISTER PURGE VALVE
To comply with legislation in fuel evaporative loss, the evaporative emissions loss control system is used on all vehicles.
Its purpose is to minimize the evaporative loss of fuel vapor from the fuel system to the atmosphere. This is achieved by
venting the fuel system through a vapor trap – a canister filled with vapor-absorbing charcoal. The charcoal acts like a
sponge and stores the vapor until the canister is purged under the control of the ECM into the engine for combustion. The
carry-over system uses the DMTL system to check for fuel tank integrity.
The canister is connected with the intake manifold, after the throttle body, via a purge valve. This valve is opened and
closed according to a PWM signal from the ECM. The system does not work properly in the case of leakage or clog-
ging within the system or if the purge valve cannot be controlled.
The canister is purged by drawing clean air through the
charcoal, which carries the hydrocarbons into the engine
where they are combusted. To maintain driveability and
emission control, purging must be closely controlled as a
1% concentration of fuel vapor from the canister in the
air intake may shift the air/fuel ratio by as much as 20%.
Purging must be carried out at regular intervals to regen-
erate the charcoal, since the storage capacity is limited.
The purge function is alternated with the fuel metering
adaptation, as both cannot be active at the same time.
The ECM alters the PWM signal to the purge valve to con-
trol the rate of purging of the canister. The purging of the
canister is done in a controlled manner in order to maintain
the correct stoichiometric air/fuel mixture for the engine.
The ECM also ensures that the canister itself is purged
frequently enough to prevent fuel saturation of the char-
coal, which could lead to an excessive buildup of fuel
vapor (and vapor pressure) in the system, increasing the
likelihood of vapor leaks. Failure Modes
• Valve drive open circuit
• Short circuit to battery voltage or ground
• Valve/pipe work blocked
• Valve stuck open
• Pipe work leaking/disconnected
• Noisy valve
Failure Symptoms
• Engine may possibly stall on return to idle (if valve
stuck open)
• Poor idling quality (if valve stuck open)
• Fuel metering adaptations forced excessively rich if canister is clear with valve stuck open
• Fuel metering adaptations forced excessively lean if canister is saturated with valve stuck open
• Saturation of canister (if valve stuck closed)
PURGE VALVE
AIR FLOWS ENS OR
THROTTLE
FUEL TANK CARBON FILTER
INTAKE
MANIFOLD
NP10V8111

3-3204/14/2009NP10-V8JLR: AJ133 5.0-Liter DFI V8 EngineTechnical Training
Crankcase Ventilation System Engine Management System
CRANKCASE VENTILATION SYSTEM
During a normal compression stroke, small amounts of
gases in the combustion chamber escape past the piston.
Approximately 70% of these gases are unburned fuel
(Hydrocarbons).
The purpose of a Positive Crankcase Ventilation (PCV)
system is to prevent crankcase pressure build-up, protect
engine seals, and remove harmful gases from the crank-
case and combine them with the engine’s normal incom-
ing air/fuel charge. The crankcase is ventilated through part-load and full-
load breathers and oil separators, which consist of a vari-
able geometry oil separator, pressure control valves, and
oil drain valve. This sophisticated system reduces oil
pullover by over half.
The integrated twin PCV valves prevent the hose from
icing and improve driveability in cold climates. The full
load breather hose purges the crankcase and reduces
condensation when the engine is cold.
NA Crankcase Ventilation System
TWIN
POS ITIVE CRANKCAS E VENTILATION VALVES
PART LOAD BREATHER TUBE FULL LOAD BREATHER TUBE
NP10V8112