1998 JAGUAR X308 idle air control valve

High
tension (electrical)
ht
Hourh
Hydro

carbon
HC
I
Idl

e Air Control
IACEl
ectrical control of throttle bypass air
Idl

e Air Control Valve
IACVStepper motor dri
ven device which vari
es the volume of air by-passing the
throttle to maintain the programmed idle speed
Ignitionign
Ignition am
plifier
IAD
evice which amplifies the i
gniti
on system output
Ignition groundIGN GND
In

ertia Fuel Shut-off
IFSAn
inertia system that shuts off the fuel supply when activated by pre-
determined force limits brough t about by (e.g.) collision
In
ertia Fuel Shut-off
Switch
IFSSShut
s down fuel and ignition systems in the event of a vehicle impact
Inta

ke air
Air drawn t
hrough a cleaner and distri
buted to each cylinder for use in
combustion
InputI/PAn
electrical input signal to a controlling device
Inta

ke Air Temperature
IATTem
perature of intake air
Inta

ke Air Temperature
Sensor
IATSDe
vice used to measure IAT
Inta

ke Air Temperature
Sensor Ignition
IATSITherm
istor which signals the ECM to retard
the ignition timing in response to
high inlet air temperatures
Inta
ke Air Temperature
Sensor Injection
IATSFTher
mistor which inputs air density information to the ECM
Internal diameteri.

dia
Inte

rnational Standards
Organization
ISO
K
Kilogramme (mass)kg
Kilogram
me (force)
kg
f
Ki

logramme force per
square centimeter
kg
f/cm2
Kilom

eter
km
Ki

lometer per hour
km
/h
Kilopasc

al
kP
a
KilovoltkV
Knock

Sensor
KSSens
or which detects the onset of detonation, and signals the ECM to retard
the ignition
L
Le
ft-hand
LH
Left-hand drive veh

icle
LHD
Le

ft-hand thread
LH Thd
Ligh

t Emitting Diode
LEDLigh
t-emitting semiconductor diode used
in alphanumeric displays and as an
indicator lamp
Liqu
id Crystal Display
LCDOp
tical digital display system, applied voltage to which varies the way the
crystals reflect light, thereby modifying the display
LiterL
Low ten
sion
ltPrim
ary circuit of the ignition system, linking the battery to the primary
winding in the ignition coil
M
Malfu
nction Indicator
Lamp
MILA
required on-board indicator to aler
t the driver of an emission related
malfunction
Mani
fold Absolute
Pressure
MAPAbsolute pressure o
f the intake manifold air
Mani

fold Absolute
Pressure Sensor
MAPSSensor loca
ted in the ECM and
ported to the intake manifold
Manifol
d Surface
Temperature
MST
Mass Ai
r Flow
MAFSy
stem which provides inform
ation on the mass flow rate of the intake air to
the engine
Mass Ai
r Flow Sensor
MAFSHot-wi
re sensor which monitors air flow
into the intake manifold for fueling
and ignition control
Maxim
um
max.

E
ngine Management System Components
Electronic Throt
tle
The
electronic throttle assembly, in resp
onse to signals from both the driver and the ECM, adjusts idle speed, sets the
throttle valve to the position requested by the driver's accelerator / throttle pedal, cruise and traction control, power
limitation and catalyst warm-up.
Mass
Air Flow Meter
The sensor i
s located in the air flow mete
r assembly and outputs an analogue voltag e to the ECM. This sensor measures air
flow into the engine inlet system and is calibrated to measure kg / hour.
In
take Air Temperature
Th
e intake air temperature sensor is loca
ted in the air flow meter assembly and outputs an analogue voltage to the ECM.
The ECM will substitute a default value eq ual to 50°C should this sensor fail.
Fuel Injectors
The eigh
t bottom fed fuel injectors are located in the fuel rails. Th
e fuel injectors are electromagnetic solenoid valves
controlled by the ECM. The pulse time for the injector combined with the fuel pr essure determines the volume of fuel
injected to the manifold.
Fue
l Delivery
The fu
el pump provides fuel to the fuel rail where the circulat
ing pressure is controlled by a pressure regulator valve; excess
fuel is returned to the fuel tank.
The pressure regulator valve is controlled by manifold depression so that fuel delivery pressure is maintained at
approximately 3 bar above manifold pressure.
Fuel Pump
Relay
The ECM controls thi

s component for normal
engine running. The security system may disable this relay via communication
with the ECM.
Fuel Lev
el Sensing
The tank fuel

is measured by the fuel le
vel sensor . This signal is used by the ECM as an in put to certain diagnostics.
Eva
porative Valve
Excess vapour

formed in the fuel tank is
absorbed into the evaporative emission pu rge control canister. While the engine is
running, the fuel absorbed in the canister is gradually purged back into the engine. The rate of purging is governed by
engine operating conditions and vapour concentration level. Operating conditions which affect the purge rate are:
2—Purge
valve
3—Engine

torque reduction
4—E

lectronic throttle assembly
5—Coo

ling fans
6—Ignition amplifier driver
7—Engine overspeed
8—Cli

mate control compressor clutch
9—O

BDII information (J1962, CAN, ISO)

10—F
uel pump relay
11—Heat

ed oxygen sensor
12—Vari

able valve timing
13—MIL sw

itching



ECM Out
puts
It

em
Par
t Number
De
scription
1—Exhaus

t gas recirculation

2.2. Cruise
3. 3. Mechanica l
guard
4. 4. Fixed idle
5. 5. Redundancy
6. 6. Full authority
7. 7. Engine shut-down
Normal mode occurs when the EC M uses the mechanical and monitoring arrangem ent of the throttle valve to control throttle
opening. The ECM does not permit driver demand to be exceeded but it can be restricted to allow for such features as
stability / traction control, or engine power limitation.
The ECM determines engine idle speed by controlling the throttle valve motor to vary the blade angle between the non-
adjustable preset limits of the mechanic al guard and the throttle valve motor.
Cruise mode is engaged as a result of the ECM calculating and controlling the required throttle valve opening via the
vacuum system. When the driver releases the throttle pedal, the input shaft disengages from the mechanical guard or the
vacuum actuator pulls the guard away from th e throttle valve. The throttle pedal will feel light should it be pushed again to
accelerate (pressing the pedal further will re-engage the input shaft with the mechanical guard and restore normal feel).
The ECM utilizes sensors to monitor the relative positions of the mechanical guard and throttle valve and adjusts them to
maintain the set cruise speed.
Mechanical guard mode permits full mechanical operation of the throttle if the ECM detects that a problem has been
encountered with the throttle valve position sensor, dc motor, associated harnesses / connecto rs or the ECM.
Fixed idle mode occurs when any two of the three sensors (two input shaft sensors and the mechanical guard sensor) fail.
The ECM will assume values which represent a blade angl e of approximately 2,5° and 1200 rpm (unloaded) maximum
engine speed.
Redundancy mode occurs when any one of the three sensors (two input shaft sensors and the mechanical guard sensor)
fails. The operational pair will be deemed to be safe to co ntinue without intervention, but cruise will be inhibited.
Full authority mode is invoked when a mech anical guard failure occurs which indicates that the guard is stuck fully open.
The red warning lamp will be lit and road speed will be li mited to 120 kph.
Engine shut-down mode will occur followin g multiple failures, such as mechanical guard mode following full authority mode
(or vice versa) or the throttle blade sticks.
Intake Elbow

The intake elbow directs the metered airflow from the electronic throttle to the intake manifold. Stub pipes on both sides of

leak
/blockage
EVAP valve failure


P0444Evaporati

ve emissions system
(EVAP) valve circuit open circuit
EVAP t
o ECM drive circuit open
circuit or high resistance
EVAP failu
re
F
or evaporative emissions pinpoint
tests,
REFER to Section 303
-1
3 Evaporative

Emiss
ions
.
P0445Evaporati

ve emissions system
(EVAP) valve circuit short circuit
E
VAP to ECM drive circuit short
circuit to ground
EVAP failu
re
F
or evaporative emissions pinpoint
tests,
REFER to Section 303
-1
3 Evaporative

Emiss
ions
.
P0447Cani

ster close valve (CCV) circuit
open circuit
CCV to ECM
drive circuit open
circuit, high resi stance or short
circuit to ground
EVAP failu
re
F
or evaporative emissions pinpoint
tests,
REFER to Section 303
-1
3 Evaporative

Emiss
ions
.
P0448Cani

ster close valve (CCV) circuit
short circuit
CCV to
ECM drive circuit short
circuit to high voltage
CCV failure

F
or evaporative emissions pinpoint
tests,
REFER to Section 303
-1
3 Evaporative

Emiss
ions
.
P0452F

uel tank pressure (FTP) sensor
circuit low voltage
FTP
sensor disconnected
FTP

sensor to ECM sense circuit
open circuit or short circuit to
ground
FTP sen
sor to ECM power supply
circuit open circuit or short circuit
to ground
F
TP sensor failure
F
or evaporative emissions pinpoint
tests,
REFER to Section 303
-1
3 Evaporative

Emiss
ions
.
P0453F

uel tank pressure (FTP) sensor
circuit high voltage
FTP
sensor to ECM signal ground
circuit open circuit
F
TP sensor to ECM wiring (supply,
sense, signal, ground) short circuit
to each other
FTP
sensor to ECM sense circuit
short circuit to high voltage
F
TP sensor failure
F
or evaporative emissions pinpoint
tests,
REFER to Section 303
-1
3 Evaporative

Emiss
ions
.
P0460Fue

l level sense signal
performance
Fue
l level sensor
to instrument
cluster circuits in termittent short or
open circuit
F
uel level sensor failure
Instrument cluster
faul
t (incorrect
fuel level data)
F
or fuel level sensor
circuit tests,
REFER to Section 303
-04
Fuel
Charging and Con

trols
.
P0506Idl

e rpm lower than expected
Ai
r intake blockage
Acce

ssory drive overload
(defective/siezed component)
Thr
ottle valve stuck closed
Throttl

e assembly failure
Chec
k the air intake system.
REFER to Section 303
-1
2 Intake Air
Distribu

tion and Filtering
.
Check t
he accessory drive
components,
REFER to Section 303
-0
5 Accessory
Dr

ive
.
F
or throttle body information,
REFER to Section 303
-04
Fuel
Charging and Con

trols
.
P0507Idle rpm

higher than expected
Inta
ke air leak between MAF
sensor and throttle
Inta
ke air leak between throttle
and engine
Engine
breather leak
Cruis

e (speed) control vacuum
failure
Thr
ottle valve stuck open
Throttl

e assembly failure
Chec
k the air intake system.
REFER to Section 303
-1
2 Intake Air
Distribu

tion and Filtering
.
Chec
k the engine breather system,
REFER to Section 303
-08
Engine
Emissi

on Control
.
F
or cruise (speed) control information,


REFER to Section 310
-03
Speed
Control.
F
or throttle body information,
REFER to Section 303
-04
Fuel
Charging and Con

trols
.
P0560Vehicle voltage

malfunction
ECM battery
power supply open
circuit, high resistance
F
or ECM power supply circuit tests,
GO to Pinpoint Test AD.
.
P0566Cruise (speed) contr
ol
CANCEL
switch ON fault
Cru
ise (speed) control switches
internal steering wheel short circuit
to ground
For cru
ise (speed) control circuit tests,


REFER to Section 310
-03
Speed