1997 JAGUAR XJ6 boot

11Reconnect the vacuum hose to the
regulator and check the fuel pressure at idle,
comparing your reading with the value listed
in this Chapter’s Specifications. Disconnect
the vacuum hose and watch the gauge - the
pressure should jump up considerably as
soon as the hose is disconnected. If it
doesn’t, check for a vacuum signal to the fuel
pressure regulator (see Step 14).
12If the fuel pressure is low, pinch the fuel
return line shut (see illustration)and watch
the gauge. If the pressure doesn’t rise, the
fuel pump is defective or there is a restriction
or leak in the fuel feed line, or the pump is
faulty. If the pressure rises sharply, renew the
pressure regulator.
13If the fuel pressure is too high, turn the
engine off. Disconnect the fuel return line and
blow through it to check for a blockage. If
there is no blockage, renew the fuel pressure
regulator.
14Connect a vacuum gauge to the pressure
regulator vacuum hose. Start the engine and
check for vacuum (see illustration). The fuel
pressure regulator receives manifold vacuum
that decreases (increases fuel pressure) when
the engine speed is raised (acceleration). If
there isn’t vacuum present, check for a
clogged hose or vacuum port. If the amount ofvacuum is adequate but the pressure is too
high, renew the fuel pressure regulator.
15Turn the ignition switch to OFF, wait five
minutes and recheck the pressure on the
gauge. Compare the reading with the
specified hold pressure. If the hold pressure is
less than specified:
a) The fuel lines may be leaking.
b) The fuel pressure regulator may be
allowing the fuel pressure to bleed
through to the return line.
c) A fuel injector (or injectors) may be
leaking.
d) The fuel pump may be defective.
4 Fuel pump-
removal and refitting
3
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. See
the Warning in Section 2.
Note 1:On early models (1988 to 1990), an
electric fuel pump is attached to the chassis
next to the fuel tank. On later models (1991 to
1994), the fuel pump is inside the fuel tank.
Note 2: On 1988 to 1990 models, the fuel
pump may chatter excessively and the engine
may stall frequently during hot weather. If
stalling occurs, the engine will restart after a
cool-down period. Dual fuel pumps can be
installed by a dealer service department or
other qualified repair facility to remedy this
problem.
1Remove the fuel tank filler cap to relieve
any pressure in the fuel tank. Relieve the fuel
pressure (see Section 2).
2Disconnect 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.
External fuel pumps
3Raise the vehicle and support it securely on
axle stands.
4Disconnect the fuel lines from the fuel pump.
5Disconnect the electrical connectors from
the fuel pump (see illustration 3.4a).
6Remove the fuel pump bracket retaining
nuts (see illustration).
7Carefully withdraw the fuel pump from the
rubber case inside the fuel pump bracket and
angle the fuel pump over the rear suspension
and out near the wheel on the left side of the
vehicle.
8Refitting is the reverse of removal.
In-tank fuel pumps
9Raise the vehicle and support it securely on
axle stands.
10Disconnect the fuel pump and fuel level
sender unit electrical connectors and the fuel
lines.
11Remove the fuel tank from the boot (see
Section 7).
12Disconnect the fuel lines from the evap-
orative flange (see illustration). Remove the
lock ring with a hammer and brass punch,
tapping the lock ring anti-clockwise.
13Withdraw the fuel pump module from the
fuel tank. Note: The fuel pump module is
4•4 Fuel and exhaust systems
3.14 Connect a vacuum gauge to the
vacuum line leading to the fuel pressure
regulator and check the vacuum source4.6 Remove the fuel pump mounting nuts
(arrowed) and slide the fuel pump out of
the rubber casing (1989 model shown)
3261 Jaguar XJ6 3.9 Check fuel pressure without vacuum applied to the fuel
pressure regulator, then with vacuum applied; fuel pressure
should DECREASE as vacuum INCREASES
3.12 Using a pair of pliers, squeeze the return line and observe
the fuel pressure increase (wrap a rag around the fuel line so you
don’t damage it)

indexed near the bottom, therefore it will be
necessary to turn the module slightly to unlock
it from the rubber holder mounted on the
bottom of the fuel tank.
14Renew the fuel pump module as a single
unit.
15Refitting is the reverse of removal.
5 Fuel level sender unit- check
and renewal
3
Warning: Petrol is highly
flammable, so take precautions
when you work on any part of
the fuel system. See the
Warning in Section 2.
Note:Some 1994 models may be equipped
with faulty fuel level sender units. A tight float
rod bushing may cause the float to stick and
indicate high fuel levels while the tank is
almost empty.
Check
1Before performing any tests on the fuel
level sender unit, completely fill the tank with
fuel.
2Remove the boot liner (see Chapter 12) to
expose the fuel level sender unit access
cover.
3Disconnect the fuel level sender unit
electrical connector located on the accesscover.Note:1991 to 1994 models are
equipped with a fuel pump module and a
sender unit assembly while 1988 and 1989
models are equipped with only the fuel level
sender unit inside the tank.
4Position the ohmmeter probes on the
electrical connector terminals (see
illustration)and check for resistance. Use the
200 ohm scale on the ohmmeter.
5With the fuel tank completely full, the
resistance should be about 18 to 20 ohms.
6Reconnect the electrical connector and
drive it until the tank is nearly empty.
7Check the resistance. The resistance of the
sender unit should be about 190 to 200 ohms.8If the readings are incorrect, renew the
sender unit. Note:The test can also be
performed with the fuel level sender unit
removed from the fuel tank. Using an
ohmmeter, check the resistance of the sender
unit with the swing arm completely down (tank
empty) and with the arm up (tank full) (see
illustration). The resistance should change
steadily from 200 ohms to around 18 ohms.
Renewal
Warning: The fuel level in the
tank must be less than half full
to safely remove the fuel
pump/sender unit assembly from the fuel
Fuel and exhaust systems 4•5
4
5.4 Connect the probes of the ohmmeter
to the fuel level sender unit terminals and
check the resistance of the float assembly5.8 An accurate check of the sender unit
can be made by removing it from the fuel
tank and observing the resistance with the
float down (empty) and then extended (full)
3261 Jaguar XJ6
4.12 Exploded view of the in-
tank fuel pump and the fuel tank
on 1991 to 1994 models

tank. If there is any doubt about the
amount of fuel in the tank, drain the fuel
tank completely before attempting this
procedure (Section 7, paragraph 1).
9Disconnect the cable from the negative
terminal of the battery. Disconnect the fuel level
sender unit/fuel pump electrical connector.
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.
10Using a brass punch, tap on the lock ring
anti-clockwise (see illustration)until the tabs
align with the indentations in the fuel tank.
11Carefully angle the sender unit out of the
opening without damaging the fuel level float
(see illustration).
12Refitting is the reverse of removal.
6 Fuel lines and fittings-
inspection and renewal
2
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. See
the Warning in Section 2.
Note:If there is a distinct knocking noise
coming from the dash when the engine is
idling, the fuel feed hose may have hardened,
restricting fuel flow and causing abnormal
sounds. Replace the fuel inlet (feed) hose with
a new one.
Inspection
1Once in a while, you will have to raise the
vehicle to service or renew some component
(an exhaust pipe hanger, for example).
Whenever you work under the vehicle, always
inspect fuel lines and all fittings and
connections for damage or deterioration.
2Check all hoses and pipes for cracks, kinks,
deformation or obstructions.
3Make sure all hoses and pipe clips attach
their associated hoses or pipes securely to
the underside of the vehicle.4Verify all hose clamps attaching rubber
hoses to metal fuel lines or pipes are a tight fit
between the hoses and pipes.
Renewal
5If you must renew any damaged sections,
use hoses or pipes constructed from exactly
the same material as the section you are
replacing. Do not refit substitutes constructed
from inferior or inappropriate material or you
could cause a fuel leak or a fire.
6Always, before detaching or disassembling
any part of the fuel line system, note the
routing of all hoses and pipes and the
orientation of all clamps and clips to assure
that new sections are identically installed.
7Before detaching any part of the fuel
system, be sure to relieve the pressure in the
tank by removing the fuel tank cap, then
relieve the fuel system pressure (Section 2).
Cover the fitting being disconnected with a
rag to absorb any fuel that may leak out.
7 Fuel tank-
removal and refitting
3
Warning: Petrol is extremely
flammable, so take extra
precautions when you work onany part of the fuel system. See the
Warning in Section 2.
1This procedure is much easier to perform if
the fuel tank is empty. Some models may have
a drain plug for this purpose. If for some reason
the drain plug can’t be removed, postpone the
job until the tank is empty or siphon the fuel
into an approved container using a siphoning
kit (available at most motor factors).
Warning: Do not start the
siphoning action by mouth!
2Remove the fuel filler cap to relieve fuel
tank pressure.
3Detach the battery negative cable.
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.
4If the tank is full or nearly full, drain the fuel
into an approved container.
5Raise the vehicle and place it securely on
axle stands.
6Remove the filler neck vent tube clamp (see
illustration)and separate the tube from the
fuel filler neck.
7Remove the fuel filler assembly bolts (see
illustration)and slide the large rubber boot
down the neck of the fuel tank. Note:These
vehicles are susceptible to clogging of the fuel
overflow line. If this happens, excess fuel or
4•6 Fuel and exhaust systems
7.6 Remove the clamp that retains the fuel
filler assembly to the filler neck7.7a Remove bolts (arrowed) that retain the
fuel filler assembly to the body and slide the
assembly down the filler neck of fuel tank
3261 Jaguar XJ6 5.10 Use a brass punch and remove the lock ring by tapping on it
in an anti-clockwise direction
5.11 Lift the fuel level sender unit assembly from the fuel tank at
an angle so as not to damage the float or arm

water in the fuel filler cap recess could flow
into the boot, causing a dangerous condition
and/or an unpleasant mess. To correct this
condition, direct low-pressure compressed air
into the overflow hole (see illustration), which
should be enough to clear any obstruction in
the line.
8Remove the spare tyre and the spare tyre
bracket assembly (see illustration).
9Disconnect the fuel lines, the vapour return
line and the canister vent line (see
illustrations). Note:Be sure to plug the hoses
to prevent leakage and contamination of the
fuel system.Remove the driveline to gain
access to the fuel line connectors next to the
tank (see Chapter 8). Working under the
vehicle, remove the pins using a needle-nose
pliers, turn the connectors slightly to loosen
them from the grommets and pull the fuel lines
out of the tank.10Remove the retaining bolts from the
fuel tank retaining straps (see illustration).
11Pull the fuel tank out into the boot area.Be careful to angle the fuel filler neck away
from the body.
12Remove the tank from the vehicle.
13Refitting is the reverse of removal.
8 Fuel tank cleaning
and repair-
general information
5
1Any repairs to the fuel tank or filler neck
should be carried out by a professional who
has experience in this critical and potentially
dangerous work. Even after cleaning and
flushing of the fuel system, explosive fumes
can remain and ignite during repair of the tank.
2If the fuel tank is removed from the vehicle,
it should not be placed in an area where
sparks or open flames could ignite the fumes
coming out of the tank. Be especially careful
inside garages where a natural petrol-type
appliance is located, because the pilot light
could cause an explosion.
9 Air cleaner assembly-
removal and refitting
1
1Detach the clips and remove the air filter
cover and the filter element (see Chapter 1).
2Remove the bolts and remove the air cleaner
assembly from the engine compartment (see
illustrations).
3Refitting is the reverse of removal.
Fuel and exhaust systems 4•7
4
7.7b Direct low pressure compressed air
into the hole for the overflow line if clogged7.8 Remove the bolts (arrowed) from the
spare tyre bracket and lift out the assembly7.9a Disconnect the flexible fuel lines from
the metal fuel lines
7.9b Disconnect the vapour return line
from the fuel tank7.9c Disconnect the canister purge line
from the fuel tank
7.9d Remove the clips (arrowed) that
retain the fuel lines to the fuel tank using
needle-nose pliers
3261 Jaguar XJ6
7.10 Remove the tank strap bolts
(arrowed) from the body
9.2a Remove the bolts (arrowed) from the
air cleaner assembly9.2b Also, remove the bolt that retains the
air intake duct to the MAF sensor and lift
the assembly from the compartment

3261 Jaguar XJ6
5
Chapter 5
Engine electrical systems
Ignition system
Ignition timing (all models) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Not adjustable
Ignition coil resistance (at 68°F):
Primary resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.4 to 0.5 ohms
Secondary resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.0 to 6.5 k-ohms
Charging system
Charging voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.9 to 15.1 volts
Standard amperage:
No load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Less than 10 amps
Full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 amps or more Amplifier - check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Alternator - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Battery cables - check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . 4
Battery check, maintenance and charging . . . . . . . . . . . See Chapter 1
Battery - emergency jump starting . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Battery - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Charging system - check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Charging system - general information and precautions . . . . . . . . . 10
CHECK ENGINE light . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 6
Distributor - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Drivebelt check, adjustment and renewal . . . . . . . . . . . See Chapter 1General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Ignition coil - check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Ignition system - check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Ignition system - general information and precautions . . . . . . . . . . . 5
Spark plug renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Spark plug lead, distributor cap and rotor check
and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Starter motor - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . 15
Starter motor - testing in vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Starter solenoid - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . 16
Starting system - general information and precautions . . . . . . . . . . 13
5•1
Specifications Contents
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
54321
1 General information
The engine electrical systems include all
ignition, charging and starting components.
Because of their engine related functions,
these components are discussed separately
from chassis electrical devices such as the
fuses, relays, lights, etc. (which are included in
Chapter 12).
Always observe the following precautions
when working on the electrical systems:
a) Be extremely careful when servicing
engine electrical components. They are
easily damaged if checked, connected or
handled improperly.
b) Never leave the ignition switch on for long
periods of time (10 minutes maximum)
with the engine off.c) Don’t disconnect the battery cables while
the engine is running.
d) Maintain correct polarity when connecting
a battery cable from another vehicle
during jump starting.
e) Always disconnect the negative cable first
and hook it up last or the battery may be
shorted by the tool being used to loosen
the cable clamps.
It’s also a good idea to review the safety-
related information regarding the engine
electrical systems in the Safety first section
near the front of this manual before beginning
any operation included in this Chapter.
2 Battery-
emergency jump starting
1
See “Jump starting”in “Roadside repairs”
at the front of this Manual.
3 Battery- removal and refitting
1
1Disconnect the negative terminal, then the
positive terminal from the battery. On 1989 to
1992 models, the battery is located in the
engine compartment on the passenger side
bulkhead and on 1993 and 1994 models, it is
located in the boot.
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.
2Remove the battery hold-down clamp.
3Lift out the battery. Be careful, it’s heavy.
4While the battery is out, inspect the carrier
(tray) for corrosion.
5If you are replacing the battery, make sure
that you get one that’s identical, with the

same dimensions, amperage rating, cold
cranking rating, etc. as the original.
6Refitting is the reverse of removal.
4 Battery cables-
check and renewal
1
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.
1Periodically inspect the entire length of
each battery cable for damage, cracked or
burned insulation and corrosion. Poor battery
cable connections can cause starting
problems and decreased engine performance.
2Check the cable-to-terminal connections at
the ends of the cables for cracks, loose wire
strands and corrosion. The presence of white,
fluffy deposits under the insulation at the
cable terminal connection is a sign that the
cable is corroded and should be renewed.
Check the terminals for distortion, missing
mounting bolts and corrosion.
3When removing the cables, always
disconnect the negative cable first and hook it
up last or the battery may be shorted by the
tool used to loosen the cable clamps. Even if
only the positive cable is being renewed, be
sure to disconnect the negative cable from
the battery first (see Chapter 1 for further
information regarding battery cable removal).
4Disconnect the cables from the battery,
then trace each of them to their opposite ends
and detach them from the starter solenoid
and earth terminals. Note the routing of each
cable to ensure correct refitting.
5If you are replacing either or both of the old
cables, take them with you when buying new
items. It is vitally important that you replace
the cables with identical parts. Cables have
characteristics that make them easy to
identify: positive cables are usually red, larger
in cross-section and have a larger diameter
battery post clamp; earth cables are usually
black, smaller in cross-section and have a
slightly smaller diameter clamp for the
negative post.
6Clean the threads of the solenoid or earth
connection with a wire brush to remove rust
and corrosion. Apply a light coat of battery
terminal corrosion inhibitor, or petroleum jelly,
to the threads to prevent future corrosion.
7Attach the cable to the solenoid or earth
connection and tighten the mounting nut/bolt
securely.
8Before connecting a new cable to the
battery, make sure that it reaches the battery
post without having to be stretched.
9Connect the positive cable first, followed by
the negative cable.
5 Ignition system- general
information and precautions
1All models are equipped with a computerised
ignition system. The ignition system consists of
the ignition coil, the crankshaft position sensor,
the amplifier and the electronic control unit
(ECU). The ignition ECU controls the ignition
timing and advance characteristics for the
engine. The ignition timing is not adjustable,
therefore, changing the position of the distributor
will not change the timing in any way. Note:In
the event the distributor must be removed from
the engine, be sure to follow the precautions
described in Section 9 and mark the engine and
distributor with paint to ensure correct refitting. If
the distributor is not marked and Ihe crankshaft is
turned while the distributor is out of the engine,
have the distributor installed by a dealer service
department. The distributor must be installed
using a special alignment tool.
2The distributor is driven by the intermediate
shaft which also drives the power steering pump.
The crankshaft position sensor is located on the
front timing cover. It detects crank position by
pulsing an electronic signal to the ECU. This
signal is sent to the ECU to provide ignition
timing specifications.
3The computerised ignition system provides
complete control of the ignition timing by
determining the optimum timing in response to
engine speed, coolant temperature, throttle
position and vacuum pressure in the intake
manifold. These parameters are relayed to the
ECU by the crankshaft position sensor, throttle
potentiometer, coolant temperature sensor and
MAF sensor. Ignition timing is altered during
warm-up, idling and warm running conditions by
the ECU. This electronic ignition system also
consists of the ignition switch, battery, coil,
distributor, spark plug leads and spark plugs.
4Refer to a dealer parts department or car
accessory outlet for any questions concerning
the availability of the distributor parts and
assemblies. Testing the crankshaft position
sensor is covered in Chapter 6.
5When working on the ignition system, take
the following precautions:
a) Do not keep the ignition switch on for
more than 10 seconds if the engine will
not start.
b) Always connect a tachometer in
accordance with the manufacturer’s
instructions. Some tachometers may be
incompatible with this ignition system.
Consult a dealer service department
before buying a tachometer for use with
this vehicle.
c) Never allow the ignition coil terminals to
touch earth. Earthing the coil could result
in damage to the igniter and/or the
ignition coil.
d) Do not disconnect the battery when the
engine is running.
6 Ignition system- check
2
Warning: Because of the high
voltage generated by the
ignition system, extreme care
should be taken when working
on the ignition components. This not only
includes the amplifier, coil, distributor and
spark plug leads, but related components
such as connectors, tachometer and other
test equipment also.
1With the ignition switch turned to the “ON”
position, a “Battery” light or an “Oil Pressure”
light is a basic check for ignition and battery
supply to the ECU.
2Check all ignition wiring connections for
tightness, cuts, corrosion or any other signs of a
bad connection.
3Use a calibrated ignition tester to verify
adequate secondary voltage (25,000 volts) at
each spark plug (see illustration). A faulty or
poor connection at that plug could also result in a
misfire. Also, check for carbon deposits inside
the spark plug boot.
4Check for carbon tracking on the coil. If
carbon tracking is evident, renew the coil and be
sure the secondary wires related to that coil are
clean and tight. Excessive wire resistance or
faulty connections could damage the coil.
5Check for battery voltage to the ignition coil
(see illustration). If battery voltage is available,
check the ignition coil primary and secondary
resistance (see Section 8).
6Check the distributor cap for any obvious
signs of carbon tracking, corroded terminals or
cracks (see Chapter 1).
7Using an ohmmeter, check the resistance of
the spark plug leads. Each wire should measure
less than 25,000 ohms.
8Check for battery voltage to the ignition
amplifier (see Section 7). If battery voltage does
not exist, check the circuit from the ignition
switch (refer to the wiring diagrams at the end of
Chapter 12).
5•2 Engine electrical systems
6.3 To use a calibrated ignition tester
(available at most car accessory outlets),
remove a plug lead from a cylinder,
connect the spark plug boot to the tester
and clip the tester to a good earth - if there
is enough voltage to fire the plug, sparks
will be clearly visible between the
electrode tip and the tester body
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)

6Be sure to buy new pads with wear
sensors. Pattern pads may not have wear
sensors; refitting pads without wear sensors
will cause the dash warning light to come on.
7To refit the new pads, reverse the removal
procedure. When refitting the caliper, be sure
to tighten the mounting bolts to the torque
listed in this Chapter’s Specifications.
8After the job is completed, depress the
brake pedal a few times to bring the pads into
contact with the discs. The pedal should be at
normal height above the floorpan and firm.
Check the brake fluid level and add enough to
top it up (see Chapter 1). Inspect carefully for
leaks and check the operation of the brakes
before placing the vehicle into normal service.
9Tighten the wheel nuts to the specified
torque.
4 Disc brake caliper- removal,
overhaul and refitting
3
Warning: Dust created by the
brake system may contain
asbestos, which is harmful to
your health. Never blow it out
with compressed air and don’t inhale any
of it. An approved filtering mask should be
worn when working on the brakes. Do not,
under any circumstances, use petroleum-
based solvents to clean brake parts. Use
brake system cleaner only!
Note 1:The following procedure applies to
both front and rear calipers.
Note 2:If an overhaul is indicated, explore all
options before beginning the job. New andfactory rebuilt calipers are available on an
exchange basis, which makes this job quite
easy. If you decide to rebuild the calipers,
make sure a rebuild kit is available before
proceeding. Always rebuild the calipers in
pairs - never rebuild just one of them.
Removal
1Loosen the wheel nuts, raise the front or
rear of the vehicle and place it securely on
axle stands. Remove the wheel.
2If you’re just removing the caliper for
access to other components, it isn’t
Braking system 9•3
9
3.5f Remove the outer brake pad3.5g Remove the inner brake pad
3.5h Pull out the wear sensor, trace the
sensor lead back to its plug, detach the
lead from the suspension, and discard it
3.5i Remove the caliper guide pins and
boots (lower pin and boot shown) . . .
3.5j . . . clean them off, inspect the pin and
boot for damage, renew as necessary,
then lubricate the pins with brake grease
and refit them in the caliper bracket
3.5k Apply anti-squeal compound to the
new brake pads
3261 Jaguar XJ6
3.5l Insert the new wear sensor into the
inner pad as shown . . .
3.5n Refit the outer pad
3.5m . . . then refit the inner pad onto the
caliper bracket
3.5o Refit the caliper, then tighten the
mounting bolts to the specified torque