1997 JAGUAR XJ6 fuel type

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

10 Accelerator cable- removal,
refitting and adjustment
3
Removal
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.
2Loosen the locknut on the threaded portion
of the throttle cable at the throttle body (see
illustration).
3Rotate the throttle lever, then slip the
throttle cable end out of the slot in the lever
(see illustration).
4Detach the throttle cable from the
accelerator pedal (see illustration).
5From inside the vehicle, pull the cable
through the bulkhead.
Refitting and adjustment
6Refitting is the reverse of removal.
7To adjust the cable, fully depress the
accelerator pedal and check that the throttle
is fully opened.
8If not fully opened, loosen the locknuts,
depress accelerator pedal and adjust the
cable until the throttle is fully open.
9Tighten the locknuts and recheck the
adjustment. Make sure the throttle closes fully
when the pedal is released (see illustration).
10After the cable is adjusted, check the
adjustment of the bellcrank. Use a small
clamp and a straight rod or stiff wire (coat
hanger) and attach it to the brake master
cylinder in such a way that the tip acts as a
pointer. Align the pointer with “A” (automatic
transmission) or “M” (manual transmission) on
the bellcrank (see illustration),depending on
what type of transmission is installed in the
vehicle.
11Slowly rotate the bellcrank until it reaches
the throttle stop (wide open throttle) andcheck to make sure the pointer aligns with the
notch in the bellcrank (see illustration).
12If necessary, adjust the position of
the throttle stop using a spanner and turn the
throttle stop screw until the bellcrank reaches
the correct position. Lock the throttle stop
screw in place.
4•8 Fuel and exhaust systems
3261 Jaguar XJ6 10.4 Remove circlip (arrowed) and separate cable from the
accelerator pedal by pulling the pin from the pedal assembly
10.2 Loosen the locknuts on the accelerator cable10.3 Rotate the bellcrank and remove the cable end from the slot
10.9 Make sure the throttle closes completely and there is a
slight amount of flex in the cable
10.10 Attach a strong wire (coat hanger)
to the master cylinder using a clamp and
align it with the notch on the bellcrank

3261 Jaguar XJ6
6
Chapter 6
Emissions and engine control systems
EGR gas temperature sensor resistance
Temperature:
212° F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 to 100 k-ohms
400° F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 to 8 k-ohms
662° F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 to 350 ohms
Torque wrench settingNm lbf ft
Crankshaft sensor bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 20 Air Injection Reactor (AIR) system . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Catalytic converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
CHECK ENGINE light . . . . . . . . . . . . . . . . . . . . . . . . . . . See Section 3
Crankcase ventilation system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Electronic control system and ECU . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Evaporative Emission Control (EVAP) system . . . . . . . . . . . . . . . . . . 6Exhaust Gas Recirculation (EGR) system . . . . . . . . . . . . . . . . . . . . . 6
Fuel tank cap gasket renewal . . . . . . . . . . . . . . . . . . . . . See Chapter 1
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Information sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
On Board Diagnosis (OBD) system -
description and fault code access . . . . . . . . . . . . . . . . . . . . . . . . . 3
6•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
To minimise pollution of the atmosphere
from incompletely burned and evaporating
gases and to maintain good driveability and
fuel economy, a number of emission control
systems are used on these vehicles. They
include the:
Air Injection Reactor (AIR) system
Crankcase Ventilation system
Exhaust Gas Recirculation (EGR) system
Electronic Fuel Injection (EFI) system
Evaporative Emission Control (EVAP)
system
Three-way catalytic converter (TWC)
system
The sections in this chapter include general
descriptions, checking procedures within the
scope of the home mechanic and component
renewal procedures (when possible) for each
of the systems listed above.
Before assuming an emissions control
system is malfunctioning, check the fuel and
ignition systems carefully (Chapters 4 and 5).
The diagnosis of some emission control
devices requires specialised tools, equipment
and training. If checking and servicing becometoo difficult or if a procedure is beyond the
scope of your skills, consult your dealer
service department or other repair workshop.
This doesn’t mean, however, that emission
control systems are particularly difficult to
maintain and repair. You can quickly and
easily perform many checks and do most of
the regular maintenance at home with
common tune-up and hand tools. Note:The
most frequent cause of emission problems is
simply a loose or broken electrical connector
or vacuum hose, so always check the
electrical connectors and vacuum hoses first.Pay close attention to any special
precautions outlined in this chapter. It should
be noted that the illustrations of the various
systems may not exactly match the system
installed on your vehicle because of changes
made by the manufacturer during production
or from year-to-year.
The Vehicle Emissions Control Information
(VECI) label and a vacuum hose diagram are
located under the bonnet (see illustrations).
These contain important emissions specifi-
cations and setting procedures, and a
vacuum hose schematic with emissions
1.6a The Vehicle Emissions Control
Information (VECI) label shows the types of
emission control systems installed, engine
information, etc (1992 model shown)
1.6b Typical vacuum hose routing label
(1992 model shown)

components identified. When servicing the
engine or emissions systems, the VECI label
in your particular vehicle should always be
checked for up-to-date information.
2 Electronic control system
and ECU
General description
Note: These models are susceptible to ECU
damage if water is allowed to build up in the
front cowl drain and overspill into the dash
area near the computer. Inspect and clear the
front cowl drain as a regular maintenance item
to keep the water draining properly. Remove
the duckbill-type rubber hose and inspect it
for clogging, collapsing or deterioration.
1The Lucas LH Engine Management system
controls the fuel injection system by means of
a microcomputer known as the Electronic
Control unit (ECU).
2The ECU receives signals from various
sensors which monitor changing engine
operating conditions such as intake air mass,
intake air temperature, coolant temperature,
engine rpm, acceleration/deceleration,
exhaust oxygen content, etc. These signals
are utilised by the ECU to determine the
correct injection duration.
3The system is analogous to the central
nervous system in the human body: The
sensors (nerve endings) constantly relay
signals to the ECU (brain), which processes
the data and, if necessary, sends out a
command to change the operating
parameters of the engine (body).
4Here’s a specific example of how one
portion of this system operates: An oxygen
sensor, located in the exhaust manifold,
constantly monitors the oxygen content of the
exhaust gas. If the percentage of oxygen in
the exhaust gas is incorrect, an electrical
signal is sent to the ECU. The ECU takes this
information, processes it and then sends a
command to the fuel injection system telling it
to change the air/fuel mixture. This happens in
a fraction of a second and it goes on
continuously when the engine is running. The
end result is an air/fuel mixture ratio which is
constantly maintained at a predetermined
ratio, regardless of driving conditions.
5In the event of a sensor malfunction, a
backup circuit will take over to provide
driveability until the problem is identified and
fixed.
Precautions
6Follow these steps:
a) Always disconnect the power by either
turning off the ignition switch or
disconnecting the battery terminals before
removing electrical connectors.
Warning: Later models are
equipped with airbags. To
prevent accidental deployment ofthe airbag, which could cause personal
injury, DO NOT work in the vicinity of the
steering column or instrument panel. The
manufacturer recommends that, on airbag
equipped models, the following procedure
should be left to a dealer service
department or other repair workshop
because of the special tools and techniques
required to disable the airbag 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.
b) When refitting a battery, be particularly
careful to avoid reversing the positive and
negative battery cables. Also, make sure
the ignition key is in the Off position when
connecting or disconnecting the battery.
c) Do not subject EFI components,
emissions-related components or the
ECU to severe impact during removal or
refitting.
d) Do not be careless during fault diagnosis.
Even slight terminal contact can invalidate
a testing procedure and damage one of
the numerous transistor circuits.
e) Never attempt to work on the ECU or
open the ECU cover. The ECU is
protected by a government-mandated
extended warranty that will be nullified if
you tamper with or damage the ECU.
f) If you are inspecting electronic control
system components during rainy weather,
make sure that water does not enter any
part. When washing the engine
compartment, do not spray these parts or
their electrical connectors with water.
g) These models are susceptible to ECU
damage if water is allowed to build up in
the front cowl drain and overspill into the
dash area. Inspect and clear the front
cowl drain system as a regular
maintenance item to keep the water
draining properly. Remove the duckbill
type rubber hose and inspect it for
clogging, collapsing or deterioration.
ECU removal and refitting
7Disconnect the negative cable from the
battery (see Chapter 5).
Warning: Later models are
equipped with airbags. To
prevent the accidental deploy-
ment of the airbag, which could
cause personal injury, DO NOT work in the
vicinity of the steering column or
instrument panel. The manufacturer
recommends that, on airbag equipped
models, the following procedure should be
left to a dealer service department or other
repair workshop because of the special
tools and techniques required to disable
the airbag 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.8Remove the lower instrument panel on the
passenger side under the glove compartment
(see Chapter 11).
9Remove the glove compartment from the
passenger compartment (see Chapter 11).
10Remove the screws from the ECU bracket
(see illustration).
11Lower the ECU and unplug the electrical
connectors.
12Refitting is the reverse of removal.
3 On Board Diagnosis (OBD)
system- description and fault
code access
2
Note: 1990 and 1991 models may set
Code 69 erroneously. If the battery voltage
drops sufficiently and the ignition key is
switched quickly from OFF to START, battery
voltage will be lowered and during cranking
causing a delayed park/neutral signal from the
decoder module to the ECU. Check all the
battery connections and the condition of the
battery and then check the rotary switch
adjustment in Chapter 7 to remedy this code.
General information
1The ECU contains a built-in self-diagnosis
system which detects and identifies
malfunctions occurring in the network. When
the ECU detects a problem, three things
happen: the CHECK ENGINE light comes on,
the fault is identified and a diagnostic code is
recorded and stored. The ECU stores the
failure code assigned to the specific problem
area until the diagnosis system is cancelled.
Note: 1988 and 1989 models are not
equipped with long term memory. It is
possible to access the codes but the operator
must remember to NOT turn the ignition key to
the OFF position after the CHECK ENGINE
light has been noticed. The codes will be lost
and it will be necessary to start the engine and
operate the vehicle through a complete drive
cycle to allow the fault code(s) to be set once
again. Instead of turning the ignition key to the
OFF position, simply stop at position II (key
ON but engine not running) to retain the fault
codes.
6•2 Emissions and engine control systems
3261 Jaguar XJ6
2.10 The ECU is located behind the
passenger’s side glovebox near the footrest
area. Remove the mounting screws
(arrowed) and carefully lower the ECU

temperature INCREASES, the resistance
values will DECREASE. A failure in this sensor
circuit should set a Code 3 (1988 and 1989)
or 13 (1990 to 1994). This code indicates a
failure in the coolant temperature sensor
circuit, so in most cases the appropriate
solution to the problem will be either repair of
a connector or wire, or renewal of the sensor.
Check
2To check the sensor, measure its resistance
value (see illustration)while it is completely
cold (60 to 80° F = 1500 to 3000 ohms). Next,
start the engine and warm it up until it reaches
operating temperature. The resistance should
be lower (180 to 200° F = 280 to 350 ohms).
3If the resistance values of the coolant
temperature sensor are correct, check the
circuit for the proper signal voltage. Turn the
ignition key ON (engine not running) and
check for reference voltage with a high-
impedance digital voltmeter (see illustration).
It should be approximately 5 volts.
Renewal
Warning: Wait until the engine is
completely cool before
beginning this procedure.
4To remove the sensor, depress the locking
tabs, unplug the electrical connector, then
carefully unscrew the sensor.
Caution: Handle the coolant sensor with
care. Damage to this sensor will affect the
operation of the entire fuel injection
system.
5Before refitting the new sensor, wrap the
threads with Teflon sealing tape to prevent
leakage and thread corrosion.
6Refitting is the reverse of removal.
Oxygen sensor
Note:An oxygen sensor splash shield is
equipped on models from VIN 664941 (mid-1990) to present. This shield prevents the self
diagnosis system from setting an intermittent
and erroneous code 44. Whenever replacing
an oxygen sensor, make sure the splash shield
is in place.
General description
7These models are equipped with a heated
oxygen sensor system. The oxygen sensor is
mounted ahead of the front catalytic converter
and monitors the exhaust gases before they
are changed. The electrical heating system
incorporated into the oxygen sensor allows for
quicker warm-up time and more efficient
oxygen content monitoring. The oxygen sensor
monitors the oxygen content of the exhaust
gas stream. The oxygen content in the exhaust
reacts with the oxygen sensor to produce a
voltage output which varies from 0.1 volts (high
oxygen, lean mixture) to 0.9 volts (low oxygen,
rich mixture). The ECU constantly monitors this
variable voltage output to determine the ratio of
oxygen to fuel in the mixture. The ECU alters
the air/fuel mixture ratio by controlling the pulse
width (open time) of the fuel injectors. A mixture
ratio of 14.7 parts air to 1 part fuel is the ideal
mixture ratio for minimising exhaust emissions,
thus allowing the catalytic converter to operate
at maximum efficiency. This ratio of 14.7 to 1 is
the one which the ECU and the oxygen sensor
attempt to maintain at all times.
8The oxygen sensor produces no voltage
when it is below its normal operating
temperature of about 600° F. During this initial
period before warm-up, the ECU operates in
open loop mode.
9If the engine reaches normal operating
temperature and/or has been running for two or
more minutes, and if the oxygen sensor is
producing a steady signal voltage below
0.45 volts at 1500 or more rpm, the ECU will set
a Code 4 (1988 and 1989) or 26 (1990 to 1994).
10When there is a problem with the oxygen
sensor or its circuit, the ECU operates in theopen loop mode - that is, it controls fuel
delivery in accordance with a programmed
default value instead of feedback information
from the oxygen sensor.
11The proper operation of the oxygen
sensor depends on four conditions:
a) Electrical - The low voltages generated by
the sensor depend upon good, clean
connections which should be checked
whenever a malfunction of the sensor is
suspected or indicated.
b) Outside air supply - The sensor is
designed to allow air circulation to the
internal portion of the sensor. Whenever
the sensor is removed and installed or
renewed, make sure the air passages are
not restricted.
c) Proper operating temperature - The ECU
will not react to the sensor signal until the
sensor reaches approximately 600° F.
This factor must be taken into
consideration when evaluating the
performance of the sensor.
d) Unleaded fuel - The use of unleaded fuel
is essential for proper operation of the
sensor. Make sure the fuel you are using
is of this type.
12In addition to observing the above
conditions, special care must be taken
whenever the sensor is serviced.
a) The oxygen sensor has a permanently
attached pigtail and electrical connector
which should not be removed from the
sensor. Damage to or removal of the
pigtail or electrical connector can
adversely affect operation of the sensor.
b) Grease, dirt and other contaminants
should be kept away from the electrical
connector and the louvered end of the
sensor.
c) Do not use cleaning solvents of any kind
on the oxygen sensor.
d) Do not drop or roughly handle the sensor.
6•4 Emissions and engine control systems
3261 Jaguar XJ6 4.2 The coolant temperature sensor is in the thermostat housing.
To check the coolant temperature sensor, use an ohmmeter to
measure the resistance between the two sensor terminals
4.3 Check for reference voltage to the electrical connector for the
coolant sensor with the ignition key ON (engine not running).
It should be approximately 5.0 volts

3261 Jaguar XJ6
12
Chapter 12
Body electrical system
1 General information
The electrical system is a 12-volt, negative
earth type. Power for the lights and all
electrical accessories is supplied by a
lead/acid-type battery which is charged by
the alternator.
This Chapter covers repair and service
procedures for the various electrical
components not associated with the engine.
Information on the battery, alternator,
distributor and starter motor will be found in
Chapter 5.
It should be noted that when portions of the
electrical system are serviced, the cable
should be disconnected from the negative
battery terminal to prevent electrical shorts
and/or fires.
2 Electrical fault finding-
general information
A typical electrical circuit consists of an
electrical component, any switches, relays,
motors, fuses, fusible links, in-line fuses or
circuit breakers related to that component
and the wiring and electrical connectors that
link the component to both the battery andthe chassis. To help you pinpoint an electrical
circuit problem, wiring diagrams are included
at the end of this Chapter.
Before tackling any troublesome electrical
circuit, first study the appropriate wiring
diagrams to get a complete understanding of
what makes up that individual circuit. Trouble
spots, for instance, can often be narrowed
down by noting if other components related to
the circuit are operating properly. If several
components or circuits fail at one time,
chances are the problem is in a fuse or earth
connection, because several circuits are often
routed through the same fuse and earth
connections.
Electrical problems usually stem from
simple causes, such as loose or corroded
connections, a blown fuse, a melted fusible
link or a bad relay. Visually inspect the
condition of all fuses, wires and connections
in a problem circuit before diagnosing it.
If testing instruments are going to be
utilised, use the diagrams to plan ahead of
time where you will make the necessary
connections in order to accurately pinpoint
the trouble spot.
The basic tools needed for electrical fault
finding include a circuit tester or voltmeter (a
12-volt bulb with a set of test leads can also
be used), a continuity tester, which includes a
bulb, battery and set of test leads, and a
jumper wire, preferably with a circuit breaker
incorporated, which can be used to bypasselectrical components. Before attempting to
locate a problem with test instruments,
use the wiring diagram(s) to decide where to
make the connections.
Voltage checks
Voltage checks should be performed if a
circuit is not functioning properly. Connect
one lead of a circuit tester to either the
negative battery terminal or a known good
earth. Connect the other lead to a electrical
connector in the circuit being tested,
preferably nearest to the battery or fuse. If the
bulb of the tester lights, voltage is present,
which means that the part of the circuit
between the electrical connector and the
battery is problem free. Continue checking the
rest of the circuit in the same fashion. When
you reach a point at which no voltage is
present, the problem lies between that point
and the last test point with voltage. Most of
the time the problem can be traced to a loose
connection. Note:Keep in mind that some
circuits receive voltage only when the ignition
key is in the Accessory or Run position.
Finding a short
One method of finding shorts in a circuit is
to remove the fuse and connect a test light or
voltmeter in its place. There should be no
voltage present in the circuit. Move the wiring
harness from side to side while watching the
test light. If the bulb goes on, there is a short Airbag system - general information . . . . . . . . . . . . . . . . . . . . . . . . . 28
Bulb renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Central locking system - description and check . . . . . . . . . . . . . . . . 25
Circuit breakers - general information . . . . . . . . . . . . . . . . . . . . . . . . 5
Cruise control system - description and check . . . . . . . . . . . . . . . . . 23
Direction indicators/hazard flashers - general information . . . . . . . . 7
Electric aerial - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . 14
Electric side view mirrors - description and check . . . . . . . . . . . . . . 26
Electric sunroof - description and check . . . . . . . . . . . . . . . . . . . . . . 27
Electric window system - description and check . . . . . . . . . . . . . . . 24
Electrical fault finding - general information . . . . . . . . . . . . . . . . . . . 2
Fuel, oil and temperature gauges - check . . . . . . . . . . . . . . . . . . . . . 11
Fuses - general information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Headlight housing (1992 to 1994 models) - removal and refitting . . . 19Headlights - adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Headlights - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Heated rear window - check and repair . . . . . . . . . . . . . . . . . . . . . . 16
Horn - check and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Ignition switch and key lock cylinder - removal and refitting . . . . . . 9
Inertia switch - description and check . . . . . . . . . . . . . . . . . . . . . . . . 22
In-line fuses - general information . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Instrument cluster - removal and refitting . . . . . . . . . . . . . . . . . . . . . 12
Instrument panel switches - removal and refitting . . . . . . . . . . . . . . 10
Radio and speakers - removal and refitting . . . . . . . . . . . . . . . . . . . 13
Relays - general information and testing . . . . . . . . . . . . . . . . . . . . . . 6
Steering column switches - removal and refitting . . . . . . . . . . . . . . . 8
Windscreen wiper motor - removal and refitting . . . . . . . . . . . . . . . . 15
Wiring diagrams - general information . . . . . . . . . . . . . . . . . . . . . . . 29
12•1
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

wash system, radio memory and the ABS
main feed and pump circuits.
In-line fuses are located through out the
vehicle depending on the year, make and
model. Consult the wiring diagrams at the end
of this Chapter for further information.
In-line fuses also have a blade terminal
design, which allow fingertip removal and
renewal. If an electrical component fails,
always check the fuse first. A blown fuse is
easily identified through the clear plastic
body. Inspect the element for evidence of
damage (see illustration 3.3).
Be sure to renew blown fuses with the
correct type. Fuses are usually colour-coded
to indicate their rating. Fuses of different
ratings are physically interchangeable, but
only fuses of the proper rating should be
used. Replacing a fuse with one of a different
value than specified is not recommended.
Each electrical circuit needs a specific
amount of protection. The amperage value of
each fuse is moulded into the fuse body.If the renewal fuse immediately fails, don’t
renew it again until the cause of the problem
is isolated and corrected. Don’t substitute
anything else for the fuse. In most cases, this
will be a short circuit in the wiring caused by a
broken or deteriorated wire.
5 Circuit breakers-
general information
Circuit breakers generally protect
components such as electric windows, central
locking and headlights. On some models the
circuit breaker resets itself automatically, so
an electrical overload in the circuit will cause it
to fail momentarily, then come back on. If the
circuit doesn’t come back on, check it
immediately. Once the condition is corrected,
the circuit breaker will resume its normal
function. Some circuit breakers have a button
on top and must be reset manually.To test a circuit breaker, use an ohmmeter
to check continuity between the terminals. A
reading of zero to 1.0 ohms indicates a good
circuit breaker. An open circuit reading on the
meter indicates a bad circuit breaker.
6 Relays- general information
and testing
2
General information
Several electrical accessories in the vehicle,
such as the fuel injection system, electric
windows, central locking, etc, use relays to
transmit the electrical signal to the component.
Relays use a low-current circuit (the control
circuit) to open and close a high-current circuit
(the power circuit). If the relay is defective, that
component will not operate properly. The
relays are mounted throughout the vehicle (see
illustrations). If a faulty relay is suspected, it
Body electrical system 12•3
12
3261 Jaguar XJ6 1988 to 1989 relay location details

3261 Jaguar XJ6
MOT test checksREF•11
MExamine the handbrake mechanism,
checking for frayed or broken cables,
excessive corrosion, or wear or insecurity of
the linkage. Check that the mechanism works
on each relevant wheel, and releases fully,
without binding.
MIt is not possible to test brake efficiency
without special equipment, but a road test can
be carried out later to check that the vehicle
pulls up in a straight line.
Fuel and exhaust systems
MInspect the fuel tank (including the filler
cap), fuel pipes, hoses and unions. All
components must be secure and free from
leaks.
MExamine the exhaust system over its entire
length, checking for any damaged, broken or
missing mountings, security of the retaining
clamps and rust or corrosion.
Wheels and tyres
MExamine the sidewalls and tread area of
each tyre in turn. Check for cuts, tears, lumps,
bulges, separation of the tread, and exposure
of the ply or cord due to wear or damage.
Check that the tyre bead is correctly seated
on the wheel rim, that the valve is sound andproperly seated, and that the wheel is not
distorted or damaged.
MCheck that the tyres are of the correct size
for the vehicle, that they are of the same size
and type on each axle, and that the pressures
are correct.
MCheck the tyre tread depth. The legal
minimum at the time of writing is 1.6 mm over
at least three-quarters of the tread width.
Abnormal tread wear may indicate incorrect
front wheel alignment.
Body corrosion
MCheck the condition of the entire vehicle
structure for signs of corrosion in load-bearing
areas. (These include chassis box sections,
side sills, cross-members, pillars, and all
suspension, steering, braking system and
seat belt mountings and anchorages.) Any
corrosion which has seriously reduced the
thickness of a load-bearing area is likely to
cause the vehicle to fail. In this case
professional repairs are likely to be needed.
MDamage or corrosion which causes sharp
or otherwise dangerous edges to be exposed
will also cause the vehicle to fail.
Petrol models
MHave the engine at normal operating
temperature, and make sure that it is in good
tune (ignition system in good order, air filter
element clean, etc).
MBefore any measurements are carried out,
raise the engine speed to around 2500 rpm,
and hold it at this speed for 20 seconds. Allowthe engine speed to return to idle, and watch
for smoke emissions from the exhaust
tailpipe. If the idle speed is obviously much
too high, or if dense blue or clearly-visible
black smoke comes from the tailpipe for more
than 5 seconds, the vehicle will fail. As a rule
of thumb, blue smoke signifies oil being burnt
(engine wear) while black smoke signifies
unburnt fuel (dirty air cleaner element, or other
carburettor or fuel system fault).
MAn exhaust gas analyser capable of
measuring carbon monoxide (CO) and
hydrocarbons (HC) is now needed. If such an
instrument cannot be hired or borrowed, a
local garage may agree to perform the check
for a small fee.
CO emissions (mixture)
MAt the time of writing, the maximum CO
level at idle is 3.5% for vehicles first used after
August 1986 and 4.5% for older vehicles.
From January 1996 a much tighter limit
(around 0.5%) applies to catalyst-equipped
vehicles first used from August 1992. If the
CO level cannot be reduced far enough to
pass the test (and the fuel and ignition
systems are otherwise in good condition) then
the carburettor is badly worn, or there is some
problem in the fuel injection system or
catalytic converter (as applicable).
HC emissionsMWith the CO emissions within limits, HC
emissions must be no more than 1200 ppm
(parts per million). If the vehicle fails this test
at idle, it can be re-tested at around 2000 rpm;
if the HC level is then 1200 ppm or less, this
counts as a pass.
MExcessive HC emissions can be caused by
oil being burnt, but they are more likely to be
due to unburnt fuel.
Diesel models
MThe only emission test applicable to Diesel
engines is the measuring of exhaust smoke
density. The test involves accelerating the
engine several times to its maximum
unloaded speed.
Note: It is of the utmost importance that the
engine timing belt is in good condition before
the test is carried out.
M
Excessive smoke can be caused by a dirty
air cleaner element. Otherwise, professional
advice may be needed to find the cause.
4Checks carried out on
YOUR VEHICLE’S EXHAUST
EMISSION SYSTEM