1998 JAGUAR X308 Speed Sensor

Default mode Definitions

MECH
ANICAL LIMP-HOME MODE:

No el
ectronic throttle operation (mechanical
operation for last quarter of pedal travel)
M
aximum 25° throttle opening,
depending on adjustment of th rottle mechanical linkage
Engine
speed restricted to 3000
rpm maximum, by fuel cut-off
Hi
gh idle speed (1200 rpm approx.)
Misfire

at idle, due to cylinder cut as a means of control
ling idle speed (the misfire will switch cylinders, as the
strategy varies th e cylinder cut)
Cruise (speed) contr
ol inhibited
REVERSE THROTTLE PROGRESSION ENABLED:
El
ectronic throttle operation, limited to maximum 25°
Cruise (speed) contr

ol inhibited
• NOTE: The throttle oper ation uses the same map as for reverse gear.
ENGINE SPEED LIMIT:
Engine
runs normally, up to 3000 rpm
Engine

speed restricted to 3000
rpm maximum, by fuel cut-off
Cruise (speed) contr
ol inhibited
LIMP-HOME UNAVAILABLE:
Cruise (speed) contr
ol inhibited
R

everse throttle pr
ogression engaged at second occurrence of DTC flagging
Diagnostic Trouble Code (D
TC) index
DT
C
Cond
ition
P
ossible Causes
Acti
on
P0171Right-hand cylinders combustion too

leanAir
intake leak between MAF
sensor and throttle
F
uel filter system blockage
F

uel injector blockage
F

uel pressure regulator failure (low

fuel pressure)
Low f
uel pump output
H0

2S harness wiring fault
E

xhaust leak (before catalyst)
ECM receivi

ng incorrect signal from

one or more of the following
sensors - ECT, MAF, IAT, TP.
Fo
r intake system,
REFER to Section 303
-12
Intake Air

Distribu
tion and Filtering
.
F
or fuel filter,
REFER to Section 310
-01
Fuel Tank
and Lines.
Chec
k the fuel injectors. Check the
fuel pressure regu lator. Check fuel
pressure. For HO2S circuit tests,
REFER to Section 303
-14
Electronic
Engine

Controls
.
F
or exhaust information,
REFER to Section 309
-00
Exhaust
Sy

stem
.
For se
nsor circuit tests,
REFER to Section 303
-14
Electronic
Engine

Controls
.
P0172Right-hand cylinders combustion too

ri
ch
Engine
misfire
Bl

ocked air filter
F

uel system return blockage
Leak

ing fuel injector(s)
F

uel pressure regulator failure
(high fuel pressure)
ECM receivi
ng incorrect signal from

one or more of the following sensors - ECT, MAF, IAT, TP
Chec
k for 'engine misfire detected'
DTCs. Check the air filter element,
REFER to Section 303
-12
Intake Air

Distribu
tion and Filtering
.
Chec
k the fuel lines,
REFER to Section 310
-01
Fuel Tank
and Lines.
Chec
k the fuel injectors,
REFER to Fuel Injectors
- in t
his
section.
For fuel pressure regulator check,GO
to Pinpoint Test D.
.
Check the fuel
pressure,

Th
e starter drive plate is attached to the rear of the crankshaft by eight bolts.
Timing Disc

A timing disc, for the engine speed sensor, is spot-w elded to the front face of the starter drive plate.
Starter Drive Plate

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

The E
VAP canister purge valve controls th
e flow rate of fuel vapour drawn into the engine during the canister purge
operation. The valve is opened by a vacu um feed from the induction elbow : the vacu um feed is controlled by the integral
valve solenoid and is applied when the so lenoid is energised. The solenoid is pulsed on (energised) and off by a fixed
frequency (100Hz) variable pulse width control signal (pulse width modulation). By varying the pulse on to off time, the
ECM controls the duty cycle of the valve (time that the valve is open to time closed) and thus the vapour flow rate to the
engine.
With no ECM signal applied to the va lve solenoid, the valve remains closed.
Can
ister Purge Operation
The
following pre-conditions are ne
cessary for purging to commence :
aft
er battery disconnection/reconnection, engine
management adaptations must be re-instated.
engine has run for
at least 8 seconds.
engi

ne coolant temperature is not less than 70 °C.
engine

not running in the fuel
cut off condition (eg overrun).
t
he adaptive fuel correction
function has not registered a rich or lean failure
t
he evaporative emission leak test has not failed
no faults have been diagnosted in th
e rel
evant sensor and valve circuits -
Air Flow Meter (AFM), Engine Coolant
Temperature sensor, Evaporativ e Canister Purge valve and Canister Close Valve (CCV).
If these conditions have been satisfied, purging is started. If any failures are registered, purging is inhibited.
The canister(s) is purged during each driv e cycle at various rates in accordance with the prevailing engine conditions. The
engine management software st ores a map of engine speed (RPM) against engine load (grams of air inducted / rev). For
any given engine speed and load, a vapour purge rate is assigned (purge rate increases with engine speed and load).
The preset purge rates are base d on the assumption of a vapour concentratio n of 100%. The actual amount of vapour is
measured by the closed loop fueling system : the input of evaporative fuel into the engine causes the outputs from the
upstream oxygen sensors to change, the am ount of change providing a measure of the vapour concentration. This feedback
causes the original purge rate to be adju sted and also reduces the amount of fuel input via the injectors to maintain the
correct air to fuel ratio.
Engine speed/load mapping and the corresp onding purge rates are different for single canister, running loss and ORVR
evaporative systems.

generates a signal when th
e dr
ive plate passes the sensor
sen
ds the ECM signals indicating crankshaft position and engine speed
is e

ssential for calculating spark timing
En

gine Coolant Temperature (ECT) Sensor
sen
ds the ECM a signal indicating the temperature of the engine coolant
is a t

emperature dependent resistor with a negative temperature coefficient (resistance changes inversely with
respect to temperature) and is constantly monitored by the ECM
Intake Air Temperature (IAT) Sensor

is m
ounted in the same housing as the MA
F sensor but is not a serviceable item
sen
ds the ECM a signal indicating the temperature of the air entering the engine
is a t

emperature dependent resistor which has a negative
temperature coefficient (its resistance changes inversely
with respect to ambient temperature).
Knock S
ensor (KS)
is a pi
ezo-electric device which sends a signal
to the ECM indicating engine detonation
Between 700 and 6800 rpm, the ECM will retard individual cylinder ignition timing when detonation occurs while allowing
the other cylinders to continue operating normally.
During acceleration, at critical load and speed conditions, the ECM retards ignition timing to prevent the onset of detonation.
H
eated Oxygen Sensor (HO2S)
are
positioned upstream of the catalytic convertor
is equipped with

a heating element wh
ich improves the response time of the sensors during engine warm-up
h
as the ability to generate a voltage signal proportional to the oxygen content of the exhaust gases leaving the
engine
pr
ovides feedback information to the ECM used to calc
ulate fuel delivery and provide optimum gas emissions
Variable V
alve Timing (VVT) Solenoid
R
efer to section 303-01.

Fue
l pump
Engine coolan

t temperature

(ECT) sensor
Blocked part-load breather (
service action S474)
Injec

tor leak
Emiss
ions
.
Check bull
etins for throttle cleaning procedure.
Check fuel pressure. For ECT sensor circuit tests,
GO to Pinpoint Test C.
. Refer to Servi
ce action
S474 for part-load breather procedure. For
injector leak test, Refer to technical service bulletin 303-39.
D
ifficult to start after hot
soak (vehicle standing
after engine has reached operating temperature)
Roc
hester valve
Thr

ottle contaminated
Purge

valve
Fue

l pump
Engine coolan

t temperature

(ECT) sensor
Blocked part-load breather (
service action S474)
Injec

tor leak
Engine cranks too
fa
st/slow
Batt
ery
Starter relay Harness Cyl

inder compression loss
(NA short term only. Refer to technical service bulletin; 303-39)
R
efer to service action
S491
F
or battery information,
REFER to Section 414
-0
1 Battery, Mounting and

Cables.
F
or starting system.
REFER to Section 303
-06 Sta
rting System
.
R
efer to technical servic
e bulletins and service
actions.
Engine

stalls
Engine st
alls soon after
start
F
uel pump relay
ECM relay Thr

ottle contaminated
CMP/CKP sen

sor
synchronization malfunction
Harness Fue
l pump
MAF

sensor malfunction
Engine coolan

t temperature

(ECT) sensor
Fue
l lines
Air leakage


F

uel pressure regulator
Check r
elay dates. Chec
k for DTCs. For fuel
pump relay tests,
REFER to Section 303
-0
4 Fuel Charging and
Controls.
F
or ECM relay tests, GO to Pinpoint Test
AD.
.
Check bull
etins for throttle cleaning procedure.
For CMP sensor circuit test s, GO to Pinpoint Test
C.
, for
CKP sensor circuit tests, GO to Pinpoint
Test N.
. Check fuel
pressure. For MAF sensor
circuit tests, GO to Pinpoint Test A.
. For EC
T
sensor tests, GO to Pinpoint Test C.
. F
or fuel
system,
REFER to Section 303
-0
4 Fuel Charging and
Controls.
and
REF
ER to Section 310
-0
1 Fuel Tank and Lines
. F

or intake system information,
REFER to Section 303
-1
2 Intake Air Distribution

and F
iltering
.
Engine

stalls on overrun
Thr
ottle contaminated
ECM relay F

uel pump relay
CMP/CKP sen

sor
synchronization malfunction
Check bull
etins for throttle cleaning procedure.
Check relay dates. For ECM relay tests, GO to Pinpoint Test AD.
. F
or fuel pump relay tests,

REFER to Section 303
-0
4 Fuel Charging and
Controls.
F
or CMP sensor circuit test
s, GO to Pinpoint Test
O.
, for
CKP sensor circuit tests, GO to Pinpoint
Test N.
.
E
ngine stalls at steady
speed, with or without cruise enabled
Thr
ottle contaminated
ECM relay F

uel pump relay
CMP/CKP sen

sor
synchronization malfunction
Harness Blocked part-load breather
(
service action S474)
Check bull
etins for throttle cleaning procedure.
Check relay dates. For EC M relay circuit tests,GO
to Pinpoint Test AD.
. F
or fuel pump relay circuit

tests,
REFER to Section 303
-0
4 Fuel Charging and
Controls.
F
or CMP sensor circuit test
s,GO to Pinpoint Test
O.
, for
CKP sensor circuit tests,GO to Pinpoint
Test N.
. Che
ck service actions.
Engine st

alls when
maneuvering
ECM relay F
uel pump relay
CMP/CKP sen

sor
synchronization malfunction
Check r
elay dates. For EC
M relay circuit tests,GO
to Pinpoint Test AD.
. F
or fuel pump relay circuit

tests,
REFER to Section 303
-0
4 Fuel Charging and
Controls.
F
or CMP sensor circuit test
s,GO to Pinpoint Test
O.
, for
CKP sensor circuit tests,GO to Pinpoint
Test N.
.

Driver Information
Chart
•

NOTE: Use this table to identify DTCs associated with the me
ssage center display, then refer to the DTC index for possible
sources and actions.
• NOTE: For definitions of Default Modes, see the foot of this table.
Poor
dr iveabilityEngine h e
sitates/poor
acceleration
Fue l
pump
Exhaus
t gas
recirculation
(EGR)
Air leakage Stop lamp swi t
ch
Throttl
e
sensors
Throttl
e
motor
Spark
plugs
fouled
Check f
o
r water ingress
into spark plug wells
Ignition coil fail
ure(s)
HT sh
o
rt to ground
(tracking) check rubber
boots for cracks/damage
ECM failu r
e
Check f
u
el pressure. For EGR information,
REFER to Section 303
-08 En gin
e Emission
Control.
F or i
ntake system information,
REFER to Section 303
-1 2
Intake Air Distribution

and F
ilt
ering
.
F or stop l
amp switch in
formation, refer to the
wiring diagrams. For throttle position sensor
tests,GO to Pinpoint Test D.
. Fo
r throttle motor
control circuit tests,GO to Pinpoint Test T.
. For
igni t
ion system,
REFER to Section 303
-07 En
gine Ignition
.
F or ECM
circuit tests,GO to Pinpoint Test
AD.
.
Engine backfiresFuel
pump
Air leakage MAF se

nsor
HO2 sensors
Spark plugs Check fo
r water ingress
into spark plug wells
HT sh o
rt to ground
(tracking) check rubber
boots for cracks/damage
Ignition coil fail
ure(s)
Chec
k fu
el pressure. For intake system
information,
REFER to Section 303
-12
Intake Air Distribution

and Filt
ering
.
F or MAF sensor ci
rcuit test
s,GO to Pinpoint Test
A.
. F or HO2 sensor
circui
t tests, check for DTC
indicating which sensor and follow indicated pinpoint test. For ignition system,
REFER to Section 303
-07 En
gine Ignition
.
Engine
s
urges
Air leakage
Fuel
pump
Stop lamp swit

ch
MAF s
e
nsor
Harness Throttl
e
sensors
Throttl
e
motor
Spark plugs
Check fo
r water ingress
into spark plug wells
HT sh o
rt to ground
(tracking) check rubber
boots for cracks/damage
ECM failu r
e
Fo
r
intake system,
REFER to Section 303
-1 2
Intake Air Distribution

and Filt
ering
.
Check fu
el pressure. For
stop lamp information,
refer to the wiring diagrams. For MAF sensor tests,GO to Pinpoint Test A.
. Fo
r throttle
position sensor tests,GO to Pinpoint Test D.
,
a n
dGO to Pinpoint Test
K.
. Fo
r throttle motor
circuit tests,GO to Pinpoint Test T.
. For ig
nition
system,
REFER to Section 303
-07 En
gine Ignition
.
F or ECM
circuit tests,GO to Pinpoint Test
AD.
.
Engine detonates/k
nocks
Fue
l
pump
HO2 sensors
Air leakage Blocked part-load breather
(s
ervice action S474)
Mass ai
r fl
ow (MAF) sensor
Chec
k fu
el pressure. Fo
r HO2 sensor circuit
tests, check for DTC indicating which sensor and
follow indicated pinpoint test. For intake system
information,
REFER to Section 303
-1 2
Intake Air Distribution

and Filt
ering
.
Check service action S474
. For MAF sensor
tests,GO to Pinpoint Test A.
.
No t
hrottle response
Traction contr
o
l invoked
Throttl
e
sensors
Throttl
e
motor
Fo
r th
rottle position sensor tests,GO to Pinpoint
Test D.
, andG O to Pinpoint
Test
K.
. Fo
r throttle

motor circuit tests,GO to Pinpoint Test T.
.
Cru i
se control inhibited or

disabled
Cru i
se control switch
Throttle

sensors
Stop lamp swit

ch
For cru
i
se control switches,
REFER to Section 310
-03
Speed Control
.
For th
rottle position sensor tests,GO to Pinpoint
Test D.
, andG O to Pinpoint
Test
K.
. For s t
op
light switch information, refer to the wiring diagrams.

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