1999 JAGUAR S TYPE ESP

V6 EngineAJ-V6/AJ28
17
Exhaust Gas Re-circulation (EGR)
Operation
The EGR system is only fitted to vehicles in NAS
markets and comprises the following
components:
¥ EGR vacuum regulator valve
¥ EGR valve
¥ differential pressure feedback EGR sensor
¥ exhaust gas feedback pipe with internal
orifice
Exhaust gas is re-circulated back to the engine
intake in proportion to a measured pressure
differential in the feedback pipe. The amount of
gas re-circulated varies primarily with engine
speed and load but is also modified by the EMS to
allow for other factors, eg coolant temperature,
and also to achieve optimum emissions and fuel
economy.
The re-circulated exhaust gas is taken from the A
bank exhaust manifold and fed into the engine via
the EGR valve. The feedback pipe contains an
internal tube with a small diameter orifice that
creates a pressure differential in the feedback
pipe. Two small pipes, connected to the feedbackpipe each side of the orifice, transmit the pressure
differential to the differential pressure feedback
EGR sensor.
The sensor consists of a transducer (a vacuum
operated variable capacitor) and a processing
circuit which convert the input pressure/vacuum
value to a corresponding analogue voltage which is
sent to the PCM. The differential pressure feedback
EGR sensor has a linear response and the
variations in exhaust pressure produce outputs in
the approximate range 1V- 3.5V dc.
The EGR vacuum regulator valve and the EGR
valve comprise the actuating components of the
control loop. The EGR vacuum regulator valve has
a vacuum input from the manifold distribution
pipes, a vacuum output to the EGR valve and
receives a pulse width modulated (PWM) signal
from the PCM. The PWM signal switches the
vacuum control output to the EGR valve according
to input demand from the differential pressure
feedback EGR sensor or in response to override
conditions determined by the engine management
system. The EGR valve is a vacuum operated
EGR SYSTEM
J.303.1282
Exhaust Gas
Feedback Pipe
Differential Pressure
Feedback EGR sensor
EGR Vacuum
Regulator Valve
EGR valve
Orifice

V6 EngineAJ-V6/AJ28
27
D.418.428
APP Sensor
303-050
APP SENSORAccelerator Pedal Position (APP)
Sensor
The APP sensor is driven directly by the pedal
pivot shaft and is connected via the wiring
harness to the powertrain control module (PCM).
The sensor is a single assembly comprising three
rotary, carbon track potentiometers with
contacting wipers. Each potentiometer has a
discrete 5V reference/return supplied from the
PCM and provides an independent analogue
output voltage to the PCM. As described for the
TP sensor, the characteristics of the three
potentiometers (angle/output voltage) differ so as
to provide unique identification to the PCM. Note
that while the TP and APP sensor characteristics,
as shown, have a general similarity, actual values
of voltage, slope and angular range for each type
of sensor is different.
Further system redundancy is provided by the use
of two pedal return springs.
Control and Operation
Drive Motor Control
The PCM does not drive the throttle motor
directly but sends duplicated control signals to the
TAC module indicating the desired throttle plate
angle. Both signals are pulse width modulated
(PWM) at 256Hz with an increase in duty cycle
indicating a corresponding (linear) increase in
desired throttle angle (ie towards full throttle).
Separate interface circuits within the PCM and
TAC module provide additional signal redundancy.
In response to PCM demand, the TAC module
processes the demand signals and generates the
current drive to the dual winding motor. An
inductive position encoder on the motor shaft
generates feedback signals to the TAC module,
providing closed loop motor control and enabling
the TAC module to maintain the desired angle.
Actual throttle plate angle is measured by the TP
sensor.
The TAC module has two separate feeds from the
vehicle 12V and ground supply, each feed (12V
and ground) being a twisted pair to reduce noise
pick up.
The TAC module also performs self diagnostic
checks:
¥ the two PWM control signals are compared
for validity
¥ the ability of the TAC module to set the
requested throttle angle is monitored¥ operation of the motor drive circuit is
checked
¥ a failed throttle return spring can be detected
¥ failure of one or both motor windings can be
detected
¥ the output of the inductive position encoder
is checked for out of range signals or failure
Diagnostic information from the TAC module is
communicated to the PCM over the twisted pair
SCP link.

V6 Engine AJ-V6/AJ28
28¥ Limp home mode in which a high idle speed
is set, with no accelerator pedal response, to
allow the vehicle to creep: the RED warning
light and FAIL SAFE ENGINE MODE message
are activated: this mode is set by, eg the loss
of two or more sensors.
¥ Engine shutdown due to serious throttle
malfunction.
J.303.1363
THROTTLE CONTROL SYSTEM
System Monitoring
Within the PCM, operation of the overall throttle
control system (main processor logic and
software) is itself monitored by a separate,
independent microprocessor, the electronic
throttle monitor. Communication is maintained
between the two processors but if it is lost or if
faults are detected by the monitor (eg throttle
angle greater than demanded), the monitor
processor may call for a restricted operating mode
such as cruise cancellation or a forced idle
condition or engine shutdown.
Failure Modes
There are four failure modes:
¥ Loss of redundancy eg a failure of one sensor
output: this type of fault causes the AMBER
warning light to illuminate and FAIL SAFE
ENGINE MODE to be displayed on the
message centre (the engine remains fully
functional).
¥ Cruise inhibit.
J.303.1363
PCM
Electronic
Throttle
Monitor
Main
Processor
SystemTAC
Module
Motor
Electronic Throttle
TP Sensor
Command 1
Command 2
SCP
APP
Sensor
Motor Winding 1
Motor Winding 2
To the TP Sensor
APP1
APP2
APP3
5V
5V
5V
5V
5V
12V
12V
TP1
TP2
TP3
Inductive
Position
Encoder

V6 EngineAJ-V6/AJ28
29
D.303.1215
FUEL RAIL AND LOWER INTAKE MANIFOLD
Fuel Supply
D.303.1215
EFT Sensor
De-pressurisation
Valve
IP Sensor
Fuel System
Returnless Fuel System
The returnless fuel system is a one way system
which delivers fuel to the engine without the
requirement for fuel to be returned to the tank.
When a return line is used, the effects of fuel
pressurisation, de-pressurisation and engine heat
on the returning fuel causes extra vapour to be
generated in the tank. With increasing regulatory
controls on evaporative emissions, this is an
undesirable condition and elimination of a fuel
return line provides significant benefits.
The in-tank fuel pump supplies fuel and regulates
pressure to the injectors under control of the PCM
and the rear electronic module (REM) and a
pressure regulator is not therefore required on the
engine fuel rail. To provide feedback for closed
loop control, an injector pressure (IP) sensor on
the fuel rail detects the pressure differentialbetween the fuel and the intake manifold and the
engine fuel temperature (EFT) sensor monitors
fuel temperature. Analogue signals from both
sensors are sent to the PCM to indicate the
pressure of the fuel and to detect whether it has
reached the vapourisation point. In response to
the sensor inputs and driver or load demands, the
PCM requests the pump system to vary the fuel
flow; in particular, fuel pressure will always be
increased to avoid vapour formation and to
maintain flow through the injectors.
Fuel pump control is further described in the
ÔS-TYPE IntroductionÕ Technical Guide.
Fuel Rail and Lower Intake Manifold
The fuel injectors are seated in two lower intake
manifolds, made of a lightweight plastic
composite material, which are fitted between the
Fuel Rail
Lower Intake
Manifold

V6 EngineAJ-V6/AJ28
43 Intake Air Temperature (IAT) Sensor
The IAT sensor is a conventional thermistor type
device which is a push fit in the intake resonator
duct.
Mass Air Flow (MAF) Sensor
The MAF sensor is an integral assembly consisting
of a hot wire sensor unit and air duct and is non-
serviceable. The assembly is fitted between the air
cleaner and intake resonator tube.
D.303.1381
MAF AND IAT SENSORS
D.303-1381
J.303.1386
HO2 SENSORS
J.303-1386
Heated Oxygen (HO2) Sensors
HO2 sensors are fitted in both the upstream and
downstream positions on the catalytic converters.
Both sensors are standard types with a step
response at the stoichiometric (lambda) air/fuel
value. The upstream sensors provide the feedback
for stoichiometric fuelling control and the
downstream sensors monitor catalyst efficiency
and also provide long term fuelling adaptation
trim.
MAF SensorIAT Sensor

V8 Engine AJ-V6/AJ28
52
J.303.1251
D.303.1268 & J.303.1251
D.303.1268
INDUCTION MANIFOLD AND THROTTLE ADAPTOR
Vacuum Connections
AAC Valve Inlet
Noise Isolation Pad
AAI Supply
Tube
Evaporative
Emissions Inlet
AAC Valve
Outlet
AAC Valve
Coolant PipesPart Load
Breather Inlet

Automatic Transmission AJ-V6/AJ28
62
D.307.321
V8 Engine Adaptor Plate
D.307.321
1. J-gate selector cable lever
2. Range switch
3. Control Module
4. Solenoid block assembly5. Filter assembly
6. Sump
7. Drain plug
Construction and Operation
The transmission housing consists of a one piece
die cast aluminium case with re-inforcement ribs
to minimise noise, vibration, and harshness
(NVH). To allow for the different physical size of
the engines, there are two transmission variants
with different overall lengths and bell housings to
match the respective engines, the V8 variant being
shorter. Different torque converters are necessary
and the V8 variant is also fitted with an adaptorplate to mate the torque converter to the larger
diameter drive plate on the V8 engine.
The main features of the transmission unit are :
¥ torque converter with a twin friction face
lock-up clutch and torsional damper
¥ geartrain consisting of three epicyclic gearsets
¥ shift elements consisting of multi-plate
clutches, brakes and one way clutches
¥ control actuators: four shift solenoids, three
variable force solenoids and a PWM 5R55N AUTOMATIC TRANSMISSION
1
3
7
6
5
24

Automatic TransmissionAJ-V6/AJ28
63 controlled solenoid are mounted on an
integral, replaceable, control module
¥ three speed sensors mounted on the external
casing: turbine speed sensor, intermediate
speed sensor and output speed sensor
¥ an oil temperature sensor is fitted inside the
transmission.
The gear select lever is connected via a Bowden
cable to an operating lever on the left side of the
transmission casing. A digital rotary switch, the
transmission range switch, fits over the shaft of
the operating lever and is fixed by two bolts to
the transmission casing. Selection of a particular
drive function generates a 4 bit binary coded
signal which is transmitted directly to the PCM
over a four wire parallel interface. As on the XK
and XJ Series, lateral movement of the gear select
lever across the gate, D to 4 or 4 to D, operates a
switch which indicates the selected function to
the PCM (the Bowden cable is not actuated
laterally).
The PCM directly controls the transmission
actuators as a response to driver demand, engine
requirements and according to the selected shift
mode. Gear selection is controlled by commands
to the four shift solenoids. If, during gear
selection, the relative speeds monitored by the
speed sensors are not as expected, the PCM
varies the analogue signal to the variable force
solenoids to increase/decrease the clutch pressure
(closed loop control). Increased engagement times
due to ageing are also controlled by adaptive shiftpressure.
Apart from the sports mode and traction mode
selected by the driver, there are pre-programmed
modes selected by the PCM in response to sensed
driving conditions :
¥ increased load such as gradients and trailer
towing
¥ cruise control
¥ hot mode: strategies including clutch lock up
are applied to reduce heat.
Transmission Oil Cooler
The transmission fluid is cooled externally by a
dedicated oil to air radiator which is mounted in
the integral cooling pack between the engine
radiator and A/C condenser and below the PAS
cooler.
D.307.320
TRANSMISSION OIL COOLING
Transmission
Oil Cooler
D.307.320