1997 JAGUAR XJ6 wiring

9Check for battery voltage to the Ignition ON
relay (see illustration). If battery voltage does
not exist, check the circuit from the ignition ON
relay to the battery (refer to the wiring diagrams
at the end of Chapter 12). Note:See Chapter 12
for the location of the Ignition ON relay.
10Check the operation of the crankshaft
position sensor (see Chapter 6).
11If all the checks are correct, check the
voltage signal from the computer. Using an LED
type test light, backprobe the coil power lead
(negative terminal) on the ignition coil (see
illustration). Remove the coil secondary wire
and earth the terminal to the engine. Now have
an assistant crank the engine over and observe
that the test light pulses on and off. If there is no
flashing from the test light, most likely the
computer is damaged. Have the ECU diagnosed
by a dealer service department.
12Additional checks should be performed by a
dealer service department or an automotive
repair workshop.
7 Amplifier- check and renewal
2
Warning: Because of the high
voltage generated by the
ignition system, extreme care
should be taken whenever an
operation is performed involving ignitioncomponents. This not only includes the
amplifier, coil, distributor and spark plug
leads, but related components such as
connectors, tachometer and other test
equipment also.
Note:Because of the complexity and the
special tools required to test the amplifier, the
following procedure only describes a test to
verify battery voltage is reaching the amplifier.
If the wiring harness and the relays are
working properly and battery voltage is
available to the amplifier, have the ignition
system and the ECU diagnosed by a dealer
service department.
Check
1Disconnect the amplifier electrical connector
(see illustration).
2Turn the ignition key ON (engine not
running), check for battery voltage (see
illustration) to the amplifier.
3If no battery voltage is present, check the
harness from the ignition switch to the
amplifier. Refer to the wiring diagrams at the
end of Chapter 12.
Renewal
4Disconnect the negative battery terminal.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.5Remove the amplifier mounting bolts (see
illustration).
6Refitting is the reverse of removal.
8 Ignition coil-
check and renewal
2
Check
1Detach the cable from the negative terminal
of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
Engine electrical systems 5•3
5
6.5 Check for battery voltage to the
coil (+) terminal6.9 Check for battery voltage
to the IGN ON relay6.11 Refit the LED test light to the coil
negative (-) terminal, crank the engine over
and observe the light flash in response to
the trigger signal from the computer
7.1 Remove the clip that retains the
harness connector to the amplifier7.2 Check for battery voltage to the
ignition amplifier
7.5 Remove the amplifier mountings
screws (arrowed) and lift the unit from the
engine compartment
3261 Jaguar XJ6

Refitting
7Insert the distributor into the engine in
exactly the same relationship to the block that
it was in when removed.
8If the distributor does not seat completely,
recheck the alignment marks between the
distributor base and the block to verify that
the distributor is in the same position it was in
before removal. Also check the rotor to see if
it’s aligned with the mark you made on the
edge of the distributor base.
9Refit the distributor hold-down bolt(s).
10The remainder of refitting is the reverse of
removal.
10 Charging system- general
information and precautions
The charging system includes the alternator,
an internal voltage regulator, a charge
indicator light, load dump module, the battery,
an ignition ON relay, an in-line fuse and the
wiring between all the components (see
illustration). The charging system supplies
electrical power for the ignition system, the
lights, the radio, etc. The alternator is driven by
a drivebelt at the front of the engine.
The purpose of the voltage regulator is to
limit the alternator’s voltage to a preset value.
This prevents power surges, circuit overloads,
etc., during peak voltage output.
The alternator load dump module protects
the electrical circuits from excessive voltage
surges. When the battery cables are removed
large amounts of transient voltage is released
through the electrical circuits. This device
diverts up to 30 load volts of excess voltage to
earth by way of a voltage dependent resistor.
The in-line fuse is a special fuse installed
into the circuit with the engine compartment
wiring harness (see Chapter 12). The in-line
fuse protects the electrical system in the
event of excess voltage surges or a power to
earth short circuit. Refer to Chapter 12 for
additional information concerning the in-line
fuses and their locations.
1993 and 1994 models have a Starter Logic
Relay. This microprocessor (computer)
gathers information from the ignition switch,
linear gear position switch, park/neutral
switch, the security switch and the electronic
door lock system. If all the conditions are in
order, the computer allows battery voltage to
be transferred from the ignition switch to the
starter/solenoid assembly.
The charging system doesn’t ordinarily
require periodic maintenance. However, the
drivebelt, battery and wires and connections
should be inspected at the intervals outlined
in Chapter 1.
The dashboard warning light should come
on when the ignition key is turned to Start,
then should go off immediately. If it remains
on, there is a malfunction in the charging
system. Some vehicles are also equipped with
a voltage gauge. If the voltage gaugeindicates abnormally high or low voltage,
check the charging system (see Section 11).
Be very careful when making electrical
circuit connections to a vehicle equipped with
an alternator and note the following:
a) When reconnecting wires to the alternator
from the battery, note their polarity.
b) Before using arc welding equipment to
repair any part of the vehicle, disconnect
the wires from the alternator and the
battery terminals.
c) Never start the engine with a battery
charger connected.
d) Always disconnect both battery leads
before using a battery charger.
e) The alternator is driven by an engine
drivebelt which could cause serious injury
if your hand, hair or clothes become
entangled in it with the engine running.
f) Because the alternator is connected
directly to the battery, it could arc or
cause a fire if overloaded or shorted out.
g) Wrap a plastic bag over the alternator and
secure it with rubber bands before steam
cleaning the engine.
11 Charging system- check
2
Note:1993 and 1994 models are equipped
with a Starter Logic Relay. This microprocessor
(computer) gathers information from theignition switch, linear gear position switch,
park/neutral switch, the security switch and the
electronic door lock system. If all the conditions
are in order, the computer allows battery
voltage to be transferred from the ignition
switch to the starter/solenoid assembly. If all
the components of the charging system are
working properly and the system still does not
charge properly, have the Starter Logic Relay
diagnosed by a dealer service department.
1If a malfunction occurs in the charging
circuit, don’t automatically assume that the
alternator is causing the problem. First check
the following items:
a) Check the drivebelt tension and its
condition. Renew it if worn or damaged.
b) Make sure the alternator mounting and
adjustment bolts are tight.
c) Inspect the alternator wiring harness and
the electrical connectors at the alternator
and voltage regulator. They must be in
good condition and tight.
d) Check the fusible link (if equipped)
located between the starter solenoid and
the alternator or the large main fuses in
the engine compartment. If it’s burned,
determine the cause, repair the circuit
and renew the link or fuse (the vehicle
won’t start and/or the accessories won’t
work if the fusible link or fuse blows).
e) Check all the in-line fuses that are in series
with the charging system circuit (see
Chapter 12).The location of these fuses
and fusible links may vary from year and
Engine electrical systems 5•5
5
10.1 Schematic of a typical charging system
3261 Jaguar XJ6

model but the designations are the same.
Refer to the wiring diagrams at the end of
Chapter 12.
f) Start the engine and check the alternator
for abnormal noises (a shrieking or
squealing sound indicates a bad bushing).
g) Check the specific gravity of the battery
electrolyte. If it’s low, charge the battery
(doesn’t apply to maintenance free
batteries).
h) Make sure that the battery is fully charged
(one bad cell in a battery can cause
overcharging by the alternator).
i) Disconnect the battery cables (negative
first, then positive). Caution:If the stereo
in your vehicle is equipped with an anti-
theft system, make sure you have the
correct activation code before
disconnecting the battery. Inspect the
battery posts and the cable clamps for
corrosion. Clean them thoroughly if
necessary (see Chapter 1). Reconnect the
positive cable, then the negative cable.
2Using a voltmeter, check the battery
voltage with the engine off. It should be
approximately 12 volts (see illustration).
3Start the engine and check the battery
voltage again. It should now be approximately
13.5 to 15.1 volts.
4Turn on the headlights. The voltage should
drop and then come back up, if the charging
system is working properly.
5If the voltage reading is greater than the
specified charging voltage, renew the
alternator.
6If you have an ammeter, connect it up to the
charging system according to its maker’s
instructions. If you don’t have a professional-
type ammeter, you can also use an inductive-
type current indicator. This device is
inexpensive, readily available at car accessory
outlets and accurate enough to perform simple
amperage checks like the following test.7With the engine running at 2000 rpm, check
the reading on the ammeter with all
accessories and lights off (no load), then again
with the high-beam headlights on and the
heater blower switch turned to the HI position
(full load). Compare your readings to the
standard amperage listed in this Chapter’s
Specifications.
8If the ammeter reading is less than standard
amperage, repair or renew the alternator.
9If the alternator is working but the charging
system still does function properly, check the
operation of the load dump module (see
illustration). Have this component checked at
a dealer service department.
12 Alternator-
removal and refitting
2
1Detach the cable from the negative terminal
of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.2Detach the electrical connectors from the
alternator.
3Loosen the alternator adjustment and pivot
bolts (see illustration) and detach the
drivebelt.
4Remove the adjustment and pivot bolts
(see illustration)from the alternator
adjustment bracket.
5If you are replacing the alternator, take the
old alternator with you when purchasing a
replacement unit. Make sure that the
new/rebuilt unit is identical to the old
alternator. Look at the terminals - they should
be the same in number, size and locations as
the terminals on the old alternator. Finally,
look at the identification markings - they will
be stamped in the housing or printed on a tag
or plaque affixed to the housing. Make sure
that these numbers are the same on both
alternators.
6Many new/rebuilt alternators do not have
a pulley installed, so you may have to switch
the pulley from the old unit to the new/rebuilt
one. When buying an alternator, find out the
policy regarding refitting of pulleys - some
shops will perform this service free of charge.
7Refitting is the reverse of removal.
5•6 Engine electrical systems
12.3 Loosen the lock bolt and back-off
the adjustment bolt (arrowed) to remove
the drivebelt12.4 Remove the pivot bolt and nut
3261 Jaguar XJ6 11.2 Connect the probes of a voltmeter to the battery terminals
and observe battery voltage with the engine OFF
and then with the engine running
11.9 The load dump module is located on the bulkhead
next to the MAF sensor

8After the alternator is installed, adjust the
drivebelt tension (see Chapter 1).
9Check the charging voltage to verify proper
operation of the alternator (see Section 11).
13 Starting system- general
information and precautions
The sole function of the starting system is
to crank the engine over quickly enough to
allow it to start.
The starting system consists of the battery,
the starter motor, the starter solenoid, the
starter relay and the electrical circuit
connecting the components. The solenoid is
mounted directly on the starter motor.
The solenoid/starter motor assembly is
installed on the upper part of the engine, next
to the transmission bellhousing.
When the ignition key is turned to the
START position, the starter solenoid is
actuated through the starter control circuit.
The starter solenoid then connects the battery
to the starter. The battery supplies the
electrical energy to the starter motor, which
does the actual work of cranking the engine.
The starter on a vehicle equipped with an
automatic transmission can be operated only
when the transmission selector lever is in Park
or Neutral.
These vehicles are equipped with either a
Bosch or Lucas starter assembly. The Lucas
unit is distinguished by the separate earth
strap from the solenoid to the starter body.
Bosch starter assemblies are equipped with a
solid metal earthing bar.
The starting system circuit is equipped with
a relay. The relay allows the ignition switch to
power the starter solenoid.
Always observe the following precautions
when working on the starting system:
a) Excessive cranking of the starter motor
can overheat it and cause serious
damage. Never operate the starter motor
for more than 15 seconds at a time
without pausing to allow it to cool for at
least two minutes.
b) The starter is connected directly to the
battery and could arc or cause a fire if
mishandled, overloaded or short circuited.
c) Always detach the cable from the
negative terminal of the battery before
working on the starting system.
Caution:If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
14 Starter motor-
testing in vehicle
2
1Make sure that the battery is charged and
that all cables, both at the battery and starter
solenoid terminals, are clean and secure.2If the starter motor does not turn at all when
the switch is operated, make sure that the
shift lever is in Neutral or Park (automatic
transmission) or that the clutch pedal is
depressed (manual transmission).
3If the starter motor spins but the engine is
not cranking, the overrunning clutch in the
starter motor is slipping and the starter motor
must be renewed.
4If, when the switch is actuated, the starter
motor does not operate at all but the solenoid
clicks, then the problem lies with either the
battery, the main solenoid contacts or the
starter motor itself (or the engine is seized).
5If the solenoid plunger cannot be heard
when the switch is actuated, the battery is
bad, the in-line fuse is burned (the circuit is
open), the starter relay (see illustration)is
defective or the starter solenoid itself is
defective.
6To check the solenoid, connect a jumper
lead between the battery (+) and the ignition
switch terminal (the small terminal) on the
solenoid. If the starter motor now operates,
the solenoid is OK and the problem is in the
ignition switch, linear switch (1988 to 1992),
rotary switch (1993 and 1994) or in the wiring.
7If the starter motor still does not operate,
remove the starter/solenoid assembly for
dismantling, testing and repair.
8If the starter motor cranks the engine at an
abnormally slow speed, first make sure that
the battery is charged and that all terminalconnections are tight. If the engine is partially
seized, or has the wrong viscosity oil in it, it
will crank slowly.
9Run the engine until normal operating
temperature is reached, then disconnect the
coil wire from the distributor cap and earth it
on the engine.
10Connect a voltmeter positive lead to the
battery positive post and connect the
negative lead to the negative post.
11Crank the engine and take the voltmeter
readings as soon as a steady figure is
indicated. Do not allow the starter motor to
turn for more than 15 seconds at a time. A
reading of nine volts or more, with the starter
motor turning at normal cranking speed, is
normal. If the reading is nine volts or more but
the cranking speed is slow, the motor is faulty.
If the reading is less than nine volts and the
cranking speed is slow, the solenoid contacts
are probably burned, the starter motor is bad,
the battery is discharged or there is a bad
connection.
15 Starter motor-
removal and refitting
2
1Detach the cable from the negative terminal
of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
2Raise the vehicle and support it securely
using axle stands.
3Drain the transmission fluid (see Chapter 7)
and remove the transmission fluid filler tube
from the transmission.
4Detach the electrical connectors from the
starter/solenoid assembly (see illustrations).
5Place a trolley jack under the tail section of
the transmission, remove the rear trans-
mission mount (see Chapter 7) and lower the
transmission slightly to gain access to the
upper transmission bellhousing bolts. Using
an extension with a swivel socket, remove the
upper starter mounting bolt (see illustration).
Engine electrical systems 5•7
5
14.5 With the ignition key ON (engine not
running), check for battery voltage to the
starter relay
15.4a Disconnect the solenoid electrical
connector at the harness connector
located near the bulkhead behind the
cylinder head (arrowed)15.4b From underneath the vehicle,
remove the battery terminal from the
solenoid (cylinder head removed
for clarity)
3261 Jaguar XJ6

e) The silicone boot must be installed in the
correct position to prevent the boot from
being melted and to allow the sensor to
operate properly.
Check
13Locate the oxygen sensor electrical
connector and inspect the oxygen sensor
heater. Disconnect the oxygen sensor
electrical connector and connect an
ohmmeter between the two terminals (see
illustration). It should be around 5 to 6 ohms.
14Also, check for proper supply voltage to
the oxygen sensor heater. Measure the voltage
with the electrical connector connected. Insert
a long pin into the backside of the electrical
connector on the correct wire. With the ignition
key ON (engine not running), check for voltage.
There should be approximately 12 volts.
Note:Battery voltage to the heater is supplied
by the main relay (1988 to 1990) or the oxygen
sensor relay (1991 to 1994). Check the
oxygen sensor relay and the wiring harness if
battery voltage is not available to the heater.
Refer to the wiring diagrams at the end of
Chapter 12 and the relay locator schematics
also in Chapter 12.
15Next, check for a millivolt signal from the
oxygen sensor. Locate the oxygen sensor
electrical connector and insert a long pin into
the oxygen sensor signal wire terminal (see
illustration). The SIGNAL wire is the single wire
with the rubber sheath covering its terminal.
16Monitor the voltage signal (millivolts) as
the engine goes from cold to warm.
17The oxygen sensor will produce a steady
voltage signal at first (open loop) of
approximately 0.1 to 0.2 volts with the engine
cold. After a period of approximately two
minutes, the engine will reach operating
temperature and the oxygen sensor will startto fluctuate between 0.1 to 0.9 volts (closed
loop). If the oxygen sensor fails to reach the
closed loop mode or there is a very long
period of time until it does switch into closed
loop mode, or if the voltage doesn’t fluctuate
well (indicating a “lazy” sensor), renew the
oxygen sensor with a new part.
Renewal
Note:Because it is installed in the exhaust
manifold or pipe, which contracts when cool,
the oxygen sensor may be very difficult to
loosen when the engine is cold. Rather than
risk damage to the sensor (assuming you are
planning to reuse it in another manifold or
pipe), start and run the engine for a minute or
two, then shut it off. Be careful not to burn
yourself during the following procedure.
18Disconnect the cable from the negative
terminal of the battery.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
19Raise the vehicle and place it securely on
axle stands.
20Disconnect the electrical connectors from
the sensor pigtail lead.
21Unscrew the oxygen sensor from the
exhaust system (see illustration).
Caution: Excessive force may damage the
threads.
22Anti-seize compound must be used on
the threads of the sensor to facilitate future
removal. The threads of new sensors will
already be coated with this compound, but if
an old sensor is removed and reinstalled,
recoat the threads.
23Refit the sensor and tighten it securely.
24Reconnect the electrical connectors to
the main engine wiring harness.25Lower the vehicle and reconnect the cable
to the negative terminal of the battery.
Throttle potentiometer
General description
26The throttle potentiometer is located on
the end of the throttle shaft on the bottom
section of the throttle body. By monitoring the
output voltage from the throttle
potentiometer, the ECU can alter fuel delivery
based on throttle valve angle (driver demand).
A broken or loose throttle potentiometer will
cause bursts of fuel from the injectors and an
unstable idle because the ECU thinks the
throttle is moving. Throttle body removal
procedures are covered in Chapter 4.
Check
27Check for the proper reference voltage to
the throttle potentiometer. Carefully back-
probe the throttle potentiometer electrical
connector using a pin on the reference voltage
wire and ground (see illustration). With the
ignition key ON (engine not running) the
reference voltage should be about 5.0 volts.
Emissions and engine control systems 6•5
6
4.21 Unscrew the oxygen sensor from the
exhaust system
3261 Jaguar XJ6 4.13 To test the oxygen sensor heater, disconnect the electrical
connector, and working on the sensor side, check the resistance
across the two terminals. Heater resistance should be 5 to 6 ohms
4.15 Refit a pin into the backside of the oxygen sensor connector
into the correct terminal and check for a millivolt output signal
generated by the sensor as it warms up. The SIGNAL wire is easily
recognised by the rubber sheath covering the terminal (arrowed)

28Check the signal voltage from the
potentiometer. Carefully backprobe the
electrical connector on the signal voltage
wire (-) with the ignition key ON (engine not
running) (see illustration). There should be
approximately 0.5 volts.
29Next, rotate the throttle lever manually and
confirm that the reference voltage increases to
approximately 4.8 volts (see illustration).
30If the voltage does not increase, renew
the throttle potentiometer with a new part.
Renewal
31Remove the throttle body from the intake
manifold (see Chapter 4).
32Remove the two mounting bolts and
separate the throttle potentiometer from the
throttle body. Note:The throttle potentiometer
is difficult to reach and adjustment requires
that the home mechanic tighten the bolts after
the final adjustment using a mirror. Be sure to
mark the mounting position of the old throttle
potentiometer before refitting the new part.
33Refitting is the reverse of removal.
Adjustment
34Refit the throttle body with the throttle
potentiometer mounting bolts just looseenough to move the potentiometer. Be sure
the bolts are tight and the potentiometer does
not rotate easily.
35Backprobe the signal wire and the ground
wire (see Step 28) and with the throttle closed
(idle position), rotate the potentiometer until
the voltmeter reads between 0.2 and 0.5 volts.
Note:The throttle potentiometer is difficult to
reach. Be sure to rotate the potentiometer
slowly and do not interfere with the voltmeter
and the electrical connectors to the gauge.
36Rotate the throttle lever and confirm that
the voltage increases to around 4.8 volts.
If the voltage range is correct, the throttle
potentiometer is installed correctly.
37Tighten the throttle potentiometer bolts. If
necessary, use a small mirror to locate the
bolts.
Mass airflow (MAF) sensor
General Information
38The mass airflow sensor (MAF) is located
on the air intake duct. This sensor uses a hot
wire sensing element to measure the amount
of air entering the engine. The air passing over
the hot wire causes it to cool. Consequently,this change in temperature can be converted
into an analogue voltage signal to the ECU
which in turn calculates the required fuel
injector pulse width.
Check
39Check for power to the MAF sensor.
Backprobe the MAF sensor electrical plug.
Working on the harness side with the ignition
ON (engine not running), check for battery
voltage on terminal number 5 (see illustration).
40Remove the pin and backprobe the MAF
sensor electrical connector terminal number 3
with the voltmeter (see illustration). The
voltage should be less than 1.0 volt with the
ignition switch ON (engine not running). Raise
the engine rpm. The signal voltage from the
MAF sensor should increase to about 2.0 volts.
It is impossible to simulate load conditions in
the driveway but it is necessary to observe the
voltmeter for a fluctuation in voltage as the
engine speed is raised. The vehicle will not be
under load conditions but MAF sensor voltage
should vary slightly.
41If the voltage readings are correct, check
the wiring harness for open circuits or a
damaged harness (see Chapter 12).
6•6 Emissions and engine control systems
4.29 . . . then check the SIGNAL voltage
with the throttle wide open. It should be
between 4.5 and 5.0 volts4.39 Check for battery voltage to the MAF
sensor on terminal number 54.40 With the engine idling, raise the engine
rpm and observe the voltage changes on
terminal number 3
3261 Jaguar XJ6 4.27 Backprobe the throttle potentiometer electrical connector
with a pin and with the ignition key ON (engine not running) there
should be 5.0 volts REFERENCE available
4.28 First check the throttle potentiometer SIGNAL voltage with the
throttle closed (idle). It should be 0.2 to 0.5 volts . . .

42Also, check the reference voltage to the
MAF sensor from the computer. Backprobe
terminal number 6 and make sure that
approximately 5 volts is present.
Renewal
43Disconnect the electrical connector from
the MAF sensor.
44Remove the air cleaner assembly (see
Chapter 4).
45Remove the four bolts and separate the
MAF sensor from the air intake duct.
46Refitting is the reverse of removal.
Intake air temperature
(IAT) sensor
General description
47The intake air temperature sensor is
located inside the air intake duct. This sensor
acts as a resistor which changes value
according to the temperature of the air entering
the engine. Low temperatures produce a high
resistance value (for example, at 68° F the
value is 2.0 to 2.6 k-ohms) while high
temperatures produce low resistance values (at
176° F the resistance is 260 to 330 ohms. The
ECU supplies around 5 volts (reference
voltage) to the air temperature sensor.
The voltage will change according to the
temperature of the incoming air. The voltage
will be high when the air temperature is cold
and low when the air temperature is warm. Any
problems with the air temperature sensor
will usually set a code 8 (1988 and 1989) or
code 16 (1990 to 1994).
Check
48To check the air temperature sensor,
disconnect the two prong electrical connector
and turn the ignition key ON but do not start
the engine.
49Measure the voltage (reference voltage),
which should be approximately 5 volts.
50If the voltage signal is not correct, havethe ECU diagnosed by a dealer service
department or other repair workshop.
51Measure the resistance across the air
temperature sensor terminals (see illustration).
The resistance should be HIGH when the air
temperature is LOW. Next, start the engine and
let it idle. Wait awhile and let the engine reach
operating temperature. Turn the ignition OFF,
disconnect the air temperature sensor and
measure the resistance across the terminals.
The resistance should be LOW when the air
temperature is HIGH. If the sensor does not
exhibit this change in resistance, renew it with a
new part.
EGR gas temperature sensor
(1991 to 1994 models)
General description
52The EGR gas temperature sensor is
mounted in the exhaust gas transfer pipe. This
sensor detects the temperature of the exhaust
moving through the EGR valve. The information
is sent to the ECU so the EGR on/off time is
regulated precisely and efficiently.
Check
53Disconnect the harness connector for the
EGR gas temperature sensor and measure
the resistance of the sensor at the various
temperatures. Refer to the Specifications
listed in this Chapter for a list of the
temperatures and the resistance values.
Removal and refitting
54Disconnect the harness connector for the
EGR gas temperature sensor and using an
open-end spanner, remove the sensor from
the EGR adapter under the intake manifold.
55Refitting is the reverse of removal.
Speed sensor
General description
56The speed sensor is mounted on thedifferential housing and monitors vehicle
speed by sensing the rotational speed of the
rear axle. A problem with this sensor or circuit
will set a code 68 and may also be the cause
of an inoperative speedometer. If the
speedometer doesn’t work, the problem lies
in the speed sensor, the instrument cluster,
the ECU or the wiring in between. For further
diagnosis, take the vehicle to a dealer service
department or other suitably-equipped and
qualified repair workshop.
Crankshaft position sensor
57The crankshaft position sensor is located
in the front timing cover near the crankshaft
pulley (see illustration). The crankshaft
position sensor relays a signal to the ECU to
indicate the exact position (angle) of the
crankshaft.
Check
58The crankshaft sensor cannot be
diagnosed without the proper tools. The
Jaguar dealer uses a diagnostic scope/
computer called the JDS. Have the crankshaft
sensor diagnosed by the dealer service
department or other qualified repair workshop.
Renewal
59To renew the sensor, disconnect the
electrical connector and remove the bolt from
the crankshaft position sensor. Refitting is the
reverse of removal.
60To renew the crankshaft sensor gear,
remove the front pulley (refer to Chapter 2A).
61Be sure there is a small gap between the
crankshaft sensor and the teeth on the gear. It
should be between 0.46 to 1.07 mm (0.018 to
0.042 inch).
62Refitting is the reverse of removal. Tighten
the crankshaft sensor bolt to the torque listed
in this Chapter’s Specifications.
Emissions and engine control systems 6•7
6
3261 Jaguar XJ6 4.51 The air intake temperature sensor resistance will DECREASE
when the temperature of the air INCREASES
4.57 Location of the crankshaft position sensor

7Start the engine and observe the vacuum
gauge. At idle, there should be no vacuum
present. Raise the engine rpm and observe
the vacuum increase. This is a ported vacuum
source and therefore it should only register
vacuum when throttled.
8Check the operation of the EGR control
solenoid. Check for battery voltage to the EGR
control solenoid harness (see illustration). If
battery voltage is not available, check the
harness. Refer to the wiring diagrams at the
end of Chapter 12.
9If battery voltage is available to the EGR
control solenoid, have the EGR system
diagnosed by a dealer service department or
other qualified repair workshop.
EGR valve renewal
10Detach the vacuum hose, disconnect the
fitting that attaches the EGR pipe to the EGR
valve and remove the EGR valve from the
exhaust manifold and check it for sticking and
heavy carbon deposits. If the valve is sticking
or clogged with deposits, clean or renew it.
11Refitting is the reverse of removal.
7 Evaporative Emission
Control (EVAP) system
Note: Some models may have charcoal
canister vent plugs installed in the canister
from the factory. These blanking plugs must
be removed to allow proper pressure and
release within the EVAP system. Check the
charcoal canister for these additional plugs
and remove them. With the blanking plugs
installed, the fuel tank will collapse causing
rough running and hesitation and loss of
power under load.
General description
1This system is designed to trap and store
fuel that evaporates from the fuel tank, throttle
body and intake manifold that would normally
enter the atmosphere in the form of
hydrocarbon (HC) emissions.
2The Evaporative Emission Control (EVAP)
system consists of a charcoal-filled canister,
the lines connecting the canister to the fuel
tank, tank pressure control valve, purgecontrol valve and thermal vacuum valve (TVV)
(see illustration). Note: 1993 and 1994
models have a purge control solenoid that is
controlled by the ECU. This solenoid switches
vacuum to the purge control valve.
3Fuel vapours are transferred from the fuel
tank and throttle body to a canister where
they’re stored when the engine isn’t running.
When the engine is running, the fuel vapours
are purged from the canister by intake airflow
and consumed in the normal combustion
process.Note: The ECU will set a code 89 if
the purge control valve is defective or the
circuit has shorted.
4The fuel tank is equipped with a pressure
control valve. This valve opens and closes
according to the pressure increase and
decrease in the fuel tank.
Check
5Poor idle, stalling and poor driveability can
all be caused by an inoperative pressure relief
valve, split or cracked hoses or hoses
connected to the wrong fittings. Check the
fuel tank filler cap for a damaged or deformed
gasket.
6Evidence of fuel loss or fuel odour can be
caused by liquid fuel leaking from fuel lines, a
cracked or damaged canister, an inoperative
fuel tank control valve, disconnected,
misrouted, kinked, deteriorated or damaged
vapour or control hoses.
7Inspect each hose attached to the canister
for kinks, leaks and cracks along its entire
length. Repair or renew as necessary.
8Look for fuel leaking from the bottom of the
6•10 Emissions and engine control systems
6.8 Check for battery voltage to the EGR
control solenoid
3261 Jaguar XJ6
7.2 Schematic of the
EVAP system