1993 FORD MONDEO steering

Chapter 6 Emissions control systems
Catalytic converter - general information, checking
and component renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Diagnosis system - general information . . . . . . . . . . . . . . . . . . . . . . 3
Electronic control system - description and precautions . . . . . . . . . 2
Engine compartment wiring check . . . . . . . . . . . . . . . See Chapter 1
EVAPorative emissions control (EVAP) system - general
information, checking and component renewal . . . . . . . . . . . . . . 5
Exhaust Gas Recirculation (EGR) system - general
information, checking and component renewal . . . . . . . . . . . . . . 6
Exhaust system check . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Information sensors - general information, testing,
removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Positive Crankcase Ventilation (PCV) system - general
information, checking and component renewal . . . . . . . . . . . . . . 8
Positive Crankcase Ventilation (PCV) system check
and filter cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Pulse-air system - general information, checking
and component renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Underbonnet hose check . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Crankshaft speed/position sensor
Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 to 450 ohms
Camshaft position sensor
Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 to 900 ohms
Intake air temperature sensor
Resistance:
At -40°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 860 to 900 k ohms
At 20°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 to 40 k ohms
At 100°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 to 2.5 k ohms
At 120°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 to 1.3 k ohms
Throttle potentiometer
Resistance - see text . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 to 6000 ohms
Power steering pressure switch
Operating pressure - green switch body:
Contacts open - infinite resistance . . . . . . . . . . . . . . . . . . . . . . . . . . 31.5 ± 3.5 bars
Contacts close - 0 to 2.5 ohms resistance . . . . . . . . . . . . . . . . . . . . Between 13.5 and 24.0 bars
Charcoal canister-purge solenoid valve
Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 to 120 ohms
Pulse-air solenoid valve
Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 to 120 ohms
Torque wrench settingsNm lbf ft
Camshaft position sensor screw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 to 23 13 to 17
Intake air temperature sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 17
Oxygen sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 44
Exhaust Gas Recirculation (EGR) system components:
Valve-to-inlet manifold bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6
Pipe-to-ignition coil screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 7
Pulse-air system components:
Filter housing mounting bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 35
Piping-to-exhaust manifold sleeve nuts . . . . . . . . . . . . . . . . . . . . . . . 32 24
6•1
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,suitable
for competent DIY
mechanicDifficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
Specifications Contents
6
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Emissions control systems 6•3
6
2.1B Location of principal fuel injection, ignition and
emissions control system components 2.1A Engine management system, showing fuel injection,
ignition and emissions control sub-systems
1 ECU (Electronic Control Unit)
2 Fuel pump/fuel gauge sender
unit
3 Fuel pump relay
4 Fuel filter
5 Idle speed control valve
6 Air mass meter
7 Air cleaner assembly
8 Fuel pressure regulator
9 Fuel rail
10 Throttle potentiometer
11 Intake air temperature sensor
12 Fuel injector
13 Camshaft position sensor
14 Charcoal canister
15 Charcoal canister-purge
solenoid valve
16 Ignition coil
17 Battery
18 Ignition module - only
separate (from ECU) on
vehicles with automatic
transmission
19 Coolant temperature sensor
20 Oxygen sensor
21 Crankshaft speed/position
sensor
22 Power supply relay
23 Power steering pressure
switch24 Air conditioning compressor
clutch solenoid
25 Service connector - for octane
adjustment
26 Self-test connector - for Ford
STAR tester diagnostic
equipment
27 Diagnosis connector - for Ford
diagnostic equipment FDS
2000
28 Ignition switch
29 Fuel cut-off switch
30 Exhaust Gas Recirculation
(EGR) solenoid valve
31 Exhaust Gas Recirculation
(EGR) valve
32 Exhaust Gas Recirculation
(EGR) exhaust gas pressure
differential sensor
33 Exhaust Gas Recirculation
(EGR) pressure differential
measuring point
34 To inlet manifold
35 Pulse-air filter housing
36 Pulse-air solenoid valve
37 Air conditioning/radiator
electric cooling fan control
38 Automatic transmission
control system - where
applicable1 ECU (Electronic Control Unit)
2 Self-test, diagnosis and service connectors
(left to right)
3 Bulkhead component mounting bracket - manual
transmission - showing from left to right, (EGR) solenoid
valve, pulse-air solenoid valve and (EGR) exhaust gas
pressure differential sensor
4 Bulkhead component mounting bracket - automatic
transmission - showing from left to right, (EGR) solenoid
valve, pulse-air solenoid valve and (EGR) exhaust gas
pressure differential sensor, with separate ignition module
above
5 Throttle housing, including potentiometer
6 Idle speed control valve
7 Intake air temperature sensor
8 Air mass meter
9 Exhaust Gas Recirculation (EGR) valve
10 Coolant temperature sensor
11 Crankshaft speed/position sensor
12 Pulse-air filter housing
13 Oxygen sensor
14 Ignition coil and spark plug (HT) leads
15 Camshaft position sensor
16 Fuel injector(s)
17 Power steering pressure switch
18 Air cleaner assembly
19 Air intake tube and resonators - under left-hand front wing
20 Resonator
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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 processes
this information, and then sends a command
to the fuel injection system, telling it to change
the air/fuel mixture; the end result is an air/fuel
mixture ratio which is constantly maintained
at a predetermined ratio, regardless of driving
conditions. This happens in a fraction of a
second, and goes on almost all the time while
the engine is running - the exceptions are that
the ECU cuts out the system and runs the
engine on values pre-programmed
(“mapped”) into its memory both while the
oxygen sensor is reaching its normal
operating temperature after the engine has
been started from cold, and when the throttle
is fully open for full acceleration.
In the event of a sensor malfunction, a
back-up circuit will take over, to provide
driveability until the problem is identified and
fixed.
Precautions
(a) Always disconnect the power by
uncoupling the battery terminals - see
Section 1 of Chapter 5 - before removing
any of the electronic control system’s
electrical connectors.
(b) When installing a battery, be particularly
careful to avoid reversing the positive and
negative battery leads.
(c) Do not subject any components of the
system (especially the ECU) to severe
impact during removal or installation.
(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, to test
it (with any kind of test equipment), or to
open its cover.
(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.
General
The various components of the fuel, ignition
and emissions control systems (not forgetting
the same ECU’s control of sub-systems such
as the radiator cooling fan, air conditioning
and automatic transmission, where
appropriate) are so closely interlinked that
diagnosis of a fault in any one component is
virtually impossible using traditional methods.
Working on simpler systems in the past, the
experienced mechanic may well have been
able to use personal skill and knowledge
immediately to pinpoint the cause of a fault, or
quickly to isolate the fault, by elimination;however, with an engine management system
integrated to this degree, this is not likely to
be possible in most instances, because of the
number of symptoms that could arise from
even a minor fault.
So that the causes of faults can be quickly
and accurately traced and rectified, the ECU
is provided with a built-in self-diagnosis
facility, which detects malfunctions in the
system’s components. When a fault occurs,
three things happen: the ECU identifies the
fault, stores a corresponding code in its
memory, and (in most cases) runs the system
using back-up values pre-programmed
(“mapped”) into its memory; some form of
driveability is thus maintained, to enable the
vehicle to be driven to a garage for attention.
Any faults that may have occurred are
indicated in the form of three-digit codes
when the system is connected (via the built-in
diagnosis or self-test connectors, as
appropriate) to special diagnostic equipment -
this points the user in the direction of the
faulty circuit, so that further tests can pinpoint
the exact location of the fault.
Given below is the procedure that would be
followed by a Ford technician to trace a fault
from scratch. Should your vehicle’s engine
management system develop a fault, read
through the procedure and decide how much
you can attempt, depending on your skill and
experience and the equipment available to
you, or whether it would be simpler to have
the vehicle attended to by your local Ford
dealer. If you are concerned about the
apparent complexity of the system, however,
remember the comments made in the fourth
paragraph of Section 1 of this Chapter; the
preliminary checks require nothing but care,
patience and a few minor items of equipment,
and may well eliminate the majority of faults.
(a) Preliminary checks
(b) Fault code read-out *
(c) Check ignition timing and base idle
speed. Recheck fault codes to establish
whether fault has been cured or not *
(d) Carry out basic check of ignition system
components. Recheck fault codes to
establish whether fault has been cured or
not *
(e) Carry out basic check of fuel system
components. Recheck fault codes to
establish whether fault has been cured or
not *
(f) If fault is still not located, carry out system
test *
Note:Operations marked with an asterisk
require special test equipment.
Preliminary checks
Note:When carrying out these checks to
trace a fault, remember that if the fault has
appeared only a short time after any part of
the vehicle has been serviced or overhauled,
the first place to check is where that work was
carried out, however unrelated it may appear,
to ensure that no carelessly-refitted
components are causing the problem.If you are tracing the cause of a “partial”
engine fault, such as lack of performance, in
addition to the checks outlined below, check
the compression pressures (see Part A of
Chapter 2) and bear in mind the possibility
that one of the hydraulic tappets might be
faulty, producing an incorrect valve clearance.
Check also that the fuel filter has been
renewed at the recommended intervals.
If the system appears completely dead,
remember the possibility that the
alarm/inhibitor system may be responsible.
1The first check for anyone without special
test equipment is to switch on the ignition,
and to listen for the fuel pump (the sound of
an electric motor running, audible from
beneath the rear seats); assuming there is
sufficient fuel in the tank, the pump should
start and run for approximately one or two
seconds, then stop, each time the ignition is
switched on. If the pump runs continuously all
the time the ignition is switched on, the
electronic control system is running in the
back-up (or “limp-home”) mode referred to by
Ford as “Limited Operation Strategy” (LOS).
This almost certainly indicates a fault in the
ECU itself, and the vehicle should therefore be
taken to a Ford dealer for a full test of the
complete system using the correct diagnostic
equipment; do not waste time trying to test
the system without such facilities.
2If the fuel pump is working correctly (or not
at all), a considerable amount of fault
diagnosis is still possible without special test
equipment. Start the checking procedure as
follows.
3Open the bonnet and check the condition
of the battery connections - remake the
connections or renew the leads if a fault is
found (Chapter 5). Use the same techniques
to ensure that all earth points in the engine
compartment provide good electrical contact
through clean, metal-to-metal joints, and that
all are securely fastened. (In addition to the
earth connection at the engine lifting eye and
that from the transmission to the
body/battery, there is one earth connection
behind each headlight assembly, and one
below the power steering fluid reservoir.)
4Referring to the information given in
Chapter 12 and in the wiring diagrams at the
back of this manual, check that all fuses
protecting the circuits related to the engine
management system are in good condition.
Fit new fuses if required; while you are there,
check that all relays are securely plugged into
their sockets.
5Next work methodically around the engine
compartment, checking all visible wiring, and
the connections between sections of the
wiring loom. What you are looking for at this
stage is wiring that is obviously damaged by
chafing against sharp edges, or against
moving suspension/transmission components
and/or the auxiliary drivebelt, by being
trapped or crushed between carelessly-
refitted components, or melted by being
forced into contact with hot engine castings,
3 Diagnosis system -
general information
6•4 Emissions control systems
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back again, as an assistant depresses the
accelerator pedal. If the valve shows any sign
of stiffness, sticking or otherwise-inhibited
movement (and the accelerator cable is
known from the previous check to be in good
condition), spray the throttle linkage with
penetrating lubricant, allow time for it to work,
and repeat the check; if no improvement is
obtained, the complete throttle housing must
be renewed (Chapter 4).
15Unclip the air cleaner cover, and check
that the air filter element and the crankcase
ventilation system filter are not clogged or
soaked. (A clogged air filter will obstruct the
intake air flow, causing a noticeable effect on
engine performance; a clogged crankcase
ventilation system filter will inhibit crankcase
“breathing”). Renew or clean the filter(s) as
appropriate; refer to the relevant Sections of
Chapter 1 for further information, if required.
Before refitting the air cleaner cover, check
that the air intake (located under the front left-
hand wing, opening behind the direction
indicator/headlight assembly) is clear. It
should be possible to blow through the intake,
or to probe it (carefully) as far as the rear of
the direction indicator light.
16Start the engine and allow it to idle.
Note:Working in the engine compartment
while the engine is running requires great care
if the risk of personal injury is to be avoided;
among the dangers are burns from contact
with hot components, or contact with moving
components such as the radiator cooling fan
or the auxiliary drivebelt. Refer to “Safety
first!” at the front of this manual before
starting, and ensure that your hands, and long
hair or loose clothing, are kept well clear of hot
or moving components at all times.
17Working from the air intake junction at the
inner wing panel, via the air cleaner assembly
and air mass meter, to the resonator, plenum
chamber, throttle housing and inlet manifold
(and including the various vacuum hoses and
pipes connected to these), check for air leaks.
Usually, these will be revealed by sucking or
hissing noises, but minor leaks may be traced
by spraying a solution of soapy water on to
the suspect joint; if a leak exists, it will be
shown by the change in engine note and the
accompanying air bubbles (or sucking-in of
the liquid, depending on the pressure
difference at that point). If a leak is found at
any point, tighten the fastening clamp and/or
renew the faulty components, as applicable.
18Similarly, work from the cylinder head, via
the manifold (and not forgetting the related
EGR and pulse-air system components) to the
tailpipe, to check that the exhaust system is
free from leaks. The simplest way of doing
this, if the vehicle can be raised and
supported safely and with complete security
while the check is made, is to temporarily
block the tailpipe while listening for the sound
of escaping exhaust gases; any leak should
be evident. If a leak is found at any point,
tighten the fastening clamp bolts and/or nuts,
renew the gasket, and/or renew the faultysection of the system, as necessary, to seal
the leak.
19It is possible to make a further check of
the electrical connections by wiggling each
electrical connector of the system in turn as
the engine is idling; a faulty connector will be
immediately evident from the engine’s
response as contact is broken and remade. A
faulty connector should be renewed to ensure
the future reliability of the system; note that
this may mean the renewal of that entire
section of the loom - see your local Ford
dealer for details.
20Switch off the engine. If the fault is not yet
identified, the next step is to check the
ignition voltages, using an engine analyser
with an oscilloscope - without such
equipment, the only tests possible are to
remove and check each spark plug in turn, to
check the spark plug (HT) lead connections
and resistances, and to check the
connections and resistances of the ignition
coil. Refer to the relevant Sections of
Chapters 1 and 5.
21The final step in these preliminary checks
would be to use an exhaust gas analyser to
measure the CO level at the exhaust tailpipe.This check cannot be made without special
test equipment - see your local Ford dealer for
details.
Fault code read-out
22As noted in the general comments at the
beginning of this Section, the preliminary
checks outlined above should eliminate the
majority of faults from the engine
management system. If the fault is not yet
identified, the next step is to connect a fault
code reader to the ECU, so that its self-
diagnosis facility can be used to identify the
faulty part of the system; further tests can
then be made to identify the exact cause of
the fault.
23In their basic form, fault code readers are
simply hand-held electronic devices, which
take data stored within an ECU’s memory and
display it when required as two- or three-digit
fault codes. The more sophisticated versions
now available can also control sensors and
actuators, to provide more effective testing;
some can store information, so that a road
test can be carried out, and any faults
encountered during the test can be displayed
afterwards.
6•6 Emissions control systems
3.26 Location and terminal identification of engine management system self-test,
diagnosis and service connectors
1 Power steering fluid reservoir
2 Diagnosis connector - for Ford diagnostic equipment FDS 2000
3 Self-test connector - for fault code read-out - pin 17 is output terminal, pin 48 is input
terminal, pin 40/60 is earth
4 Service connector - for octane adjustment
5 Plug-in bridge - to suit 95 RON fuel
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24Ford specify the use of their STAR (Self-
Test Automatic Readout) tester; most Ford
dealers should have such equipment, and the
staff trained to use it effectively. The only
alternatives are as follows:
(a) To obtain one of those proprietary readers
which can interpret EEC-IV three-digit
codes - at present, such readers are too
expensive for the DIY enthusiast, but are
becoming more popular with smaller
specialist garages.
(b) To use an analogue voltmeter, whereby
the stored codes are displayed as sweeps
of the voltmeter needle. This option limits
the operator to a read-out of any codes
stored - ie, there is no control of sensors
and/or actuators - but can still be useful in
pinpointing the faulty part of the engine
management system. The display is
interpreted as follows. Each code
(whether fault code or
command/separator) is marked by a
three-to-four second pause - code “538”
would therefore be shown as long (3 to
4 seconds) pause, five fast sweeps of the
needle, slight (1 second) pause, three fast
sweeps, slight pause, eight fast sweeps,
long pause.
(c) Owners without access to such
equipment must take the vehicle to a Ford
dealer, or to an expert who has similar
equipment and the skill to use it.
25Because of the variations in the design of
fault code readers, it is not possible to give
exact details of the sequence of tests; the
manufacturer’s instructions must be followed,
in conjunction with the codes given below.
The following ten paragraphs outline the
procedure to be followed using a version of
the Ford STAR tester, to illustrate the general
principles, as well as notes to guide the owner
using only a voltmeter.
26The vehicle must be prepared by applying
the handbrake, switching off the air
conditioning (where fitted) and any other
electrical loads (lights, heated rear window,
etc), then selecting neutral (manual
transmission) or the “P” position (automatic
transmission). Where the engine is required to
be running, it must be fully warmed-up to
normal operating temperature before the test
is started. Using any adaptors required,
connect the fault code reader to the system
via the (triangular, three-pin) self-test
connector on the right-hand end of the engine
compartment bulkhead (see illustration). If a
voltmeter is being used, connect its positive
lead to the battery positive terminal, and its
negative lead to the self-test connector’s
output terminal, pin 17. Have a pen and paper
ready to write down the codes displayed.
27Set the tester in operation. For the Ford
STAR tester, a display check will be carried
out and the test mode requirements must be
entered. If a voltmeter is being used, connect
a spare length of wire to earth the self-test
connector’s input terminal, pin 48. Be very
careful to ensure that you earth the correctterminal - the one with the white/green wire.
The first part of the test starts, with the
ignition switched on, but with the engine off.
On pressing the “Mem/test” button, the tester
displays “TEST” and the ready code “000”,
followed by a command code “010” - the
accelerator pedal must be fully depressed
within 10 seconds of the command code
appearing, or fault codes “576” or “577” will
appear when they are called up later. If a
voltmeter is being used, code “000” will not
appear (except perhaps as a flicker of the
needle) and “010” will appear as a single
sweep - to ensure correct interpretation of the
display, watch carefully for the interval
between the end of one code and the
beginning of the next, otherwise you will
become confused and misinterpret the read-
out.
28The tester will then display the codes for
any faults in the system at the time of the test.
Each code is repeated once; if no faults are
present, code “111” will be displayed. If a
voltmeter is being used, the pause between
repetitions will vary according to the
equipment in use and the number of faults in
the system, but was found to be
approximately 3 to 4 seconds - it may be
necessary to start again, and to repeat the
read-out until you are familiar with what you
are seeing.
29Next the tester will display code “010”
(now acting as a separator), followed by the
codes for any faults stored in the ECU’s
memory; if no faults were stored, code “111”
will be displayed.
30When prompted by the tester, the
operator must next depress the accelerator
pedal fully; the tester then checks several
actuators. Further test modes include a
“wiggle test” facility, whereby the operator
can check the various connectors as
described in paragraph 19 above (in this case,
any fault will be logged and the appropriate
code will be displayed), a facility for recalling
codes displayed, and a means for clearing the
ECU’s memory at the end of the test
procedure when any faults have been
rectified.
31The next step when using the Ford STAR
tester is to conduct a test with the engine
running. With the tester set in operation (see
paragraph 26 above) the engine is started and
allowed to idle. On pressing the “Mem/test”
button, the tester displays “TEST”, followed
by one of two codes, as follows.
32If warning code “998” appears, followed
by the appropriate fault code, switch off and
check as indicated the coolant temperature
sensor, the intake air temperature sensor, the
air mass meter, the throttle potentiometer
and/or their related circuits, then restart the
test procedure.
33If command code “020” appears, carry
out the following procedure within ten
seconds:
(a) Depress the brake pedal fully.
(b) Turn the steering to full-lock (either way)and centre it again, to produce a signal
from the power steering pressure switch -
if no signal is sent, fault code “521” will
be displayed.
(c) If automatic transmission is fitted, switch
the overdrive cancel button on and off,
then do the same for the
“Economy/Sport” mode switch.
(d) Wait for separator code “010” to be
displayed, then within 10 seconds,
depress the accelerator pedal fully,
increasing engine speed rapidly above
3000 rpm - release the pedal.
34Any faults found in the system will be
logged and displayed. Each code is repeated
once; if no faults are present, code “111” will
be displayed.
35When the codes have been displayed for
all faults logged, the ECU enters its “Service
Adjustment Programme”, as follows:
(a) The programme lasts for 2 minutes.
(b) The idle speed control valve is
deactivated, and the idle speed is set to
its pre-programmed (unregulated) value. If
the appropriate equipment is connected,
the base idle speed can be checked
(note, however, that it is not adjustable).
(c) The ignition timing can be checked if a
timing light is connected (note, however,
that it is not adjustable).
(d) Pressing the accelerator pedal fully at any
time during this period will execute a
cylinder balance test. Each injector in turn
is switched off, and the corresponding
decrease in engine speed is logged -
code “090” will be displayed if the test is
successful.
(e) At the end of the 2 minutes, the
completion of the programme is shown
by the engine speed briefly rising, then
returning to normal idling speed as
the idle speed control valve is
reactivated.
36As with the engine-off test, further test
modes include a “wiggle test” facility,
whereby the operator can check the various
connectors as described in paragraph 19
above (in this case, any fault will be logged
and the appropriate code will be displayed), a
facility for recalling codes displayed, and a
means for clearing the ECU’s memory at the
end of the test procedure when any faults
have been rectified. If equipment other than
the Ford STAR tester is used, the ECU’s
memory can be cleared by disconnecting the
battery - if this is not done, the code will
reappear with any other codes in the event of
subsequent trouble, but remember that other
systems with memory (such as the clock and
audio equipment) will also be affected. Should
it become necessary to disconnect the
battery during work on any other part of the
vehicle, first check to see if any fault codes
have been logged.
37Given overleaf are the possible codes,
their meanings, and where relevant, the action
to be taken as a result of a code being
displayed.
Emissions control systems 6•7
6
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Code Meaning Action327 EGR system exhaust gas pressure
differential sensor or solenoid valve Check components (Section 6 of this Chapter)
328 EGR system solenoid valve Check component (Section 6 of this Chapter)
332 EGR valve not opening Check component (Section 6 of this Chapter)
334 EGR system solenoid valve Check component (Section 6 of this Chapter)335 EGR system exhaust gas pressure
differential sensor Check component (Section 6 of this Chapter)
336 Exhaust gas pressure too high Check system (Section 6 of this Chapter)337 EGR system exhaust gas pressure
differential sensor or solenoid valve Check components (Section 6 of this Chapter)
338, 339 Coolant temperature sensor Carry out system test (see below)
341 Service connector earthed Unplug connector and repeat test - reconnect on completion
411 Engine speed too low during test Check for air leaks, then repeat test
412 Engine speed too high during test Check for air leaks, then repeat test
413 to 416 Idle speed control valve Check component (Chapter 4, Section 16)
452 Vehicle speed sensor Check component (Section 4 of this Chapter)
511, 512 ECU memory Check whether battery was disconnected, then check fuse 11 - if fault still
exists, renew ECU (Section 6 of this Chapter)
513 ECU reference voltage Carry out system test (see below)
519, 521 Power steering pressure switch not Check component is fitted and connected, then repeat test - if fault still
operated during test exists, carry out system test (see below)
522, 523 Selector lever position sensor Check component (Chapter 7, Part B)
536 Brake on/off switch not activated
during test Repeat test
538 Operator error during test Repeat test
539 Air conditioning switched on during test Switch off and repeat test
542, 543 Fuel pump circuit Carry out system test (see below)
551 Idle speed control valve circuit Carry out system test (see below)
552 Pulse-air system circuit Carry out system test (see below)
556 Fuel pump circuit Check fuel pump relay - if fault still exists, carry out system test (see below)
558 EGR system solenoid valve circuit Carry out system test (see below)
563 Radiator (high-speed) electric
cooling fan relay and/or circuit Carry out system test (see below)564 Radiator electric cooling fan relay
and/or circuit Carry out system test (see below)
565 Charcoal canister-purge solenoid valve Check component (Section 5 of this Chapter)573 Radiator electric cooling fan relay
and/or circuit Carry out system test (see below)
574 Radiator (high-speed) electric
cooling fan relay and/or circuit Carry out system test (see below)575 Fuel pump and/or fuel cut-off
switch circuits Carry out system test (see below)
576, 577 Accelerator pedal not depressed fully during
test procedure - automatic transmission
kickdown not activated Repeat test
621 Automatic transmission shift solenoid 1 circuit Refer to Chapter 7, Part B
622 Automatic transmission shift solenoid 2 circuit Refer to Chapter 7, Part B
624 Automatic transmission electronic
pressure control solenoid Refer to Chapter 7, Part B
625 Automatic transmission electronic
pressure control solenoid circuit Refer to Chapter 7, Part B
629 Automatic transmission torque
converter clutch solenoid Refer to Chapter 7, Part B
634 Selector lever position sensor circuit Check component (Chapter 7, Part B)
635, 637 Automatic transmission fluid temperature sensor Refer to Chapter 7, Part B
639 Automatic transmission speed sensor Refer to Chapter 7, Part B
645 Automatic transmission 1st speed Refer to Chapter 7, Part B
646 Automatic transmission 2nd speed Refer to Chapter 7, Part B
647 Automatic transmission 3rd speed Refer to Chapter 7, Part B
648 Automatic transmission 4th speed Refer to Chapter 7, Part B
653 Automatic transmission overdrive
cancel button and “Economy/Sport”
mode switch not operated during test Repeat test
998 Warning code Check fault(s) indicated by subsequent code(s)
Emissions control systems 6•9
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passes the sensor tip, a signal is generated,
which is used by the ECU to determine engine
speed.
4The ridge between the 35th and 36th holes
(corresponding to 90° BTDC) is missing - this
step in the incoming signals is used by the
ECU to determine crankshaft (ie, piston)
position.
Camshaft position sensor
5This is bolted to the rear left-hand end of
the cylinder head, to register with a lobe on
the inlet camshaft. It functions in the same
way as the crankshaft speed/position sensor,
producing a series of pulses (corresponding
to No 1 cylinder at 46° ATDC); this gives the
ECU a reference point, to enable it to
determine the firing order, and operate the
injectors in the appropriate sequence.
Coolant temperature sensor
6This component, which is screwed into the
top of the thermostat housing, is an NTC
(Negative Temperature Coefficient) thermistor
- that is, a semi-conductor whose electrical
resistance decreases as its temperature
increases. It provides the ECU with a
constantly-varying (analogue) voltage signal,
corresponding to the temperature of the
engine coolant. This is used to refine the
calculations made by the ECU, when
determining the correct amount of fuel
required to achieve the ideal air/fuel mixture
ratio.
Intake air temperature sensor
7This component, which is screwed into the
underside of the air intake resonator, is also an
NTC thermistor - see the previous paragraph -
providing the ECU with a signal corresponding
to the temperature of air passing into the
engine. This is used to refine the calculations
made by the ECU, when determining the
correct amount of fuel required to achieve the
ideal air/fuel mixture ratio.
Throttle potentiometer
8This is mounted on the end of the throttle
valve spindle, to provide the ECU with a
constantly-varying (analogue) voltage signal
corresponding to the throttle opening. This
allows the ECU to register the driver’s input
when determining the amount of fuel required
by the engine.
Vehicle speed sensor
9This component is a Hall-effect generator,
mounted on the transmission’s speedometer
drive. It supplies the ECU with a series of
pulses corresponding to the vehicle’s road
speed, enabling the ECU to control features
such as the fuel shut-off on the overrun, and
to provide information for the trip computer,
adaptive damping and cruise control systems
(where fitted).
Power steering pressure switch
10This is a pressure-operated switch,
screwed into the power steering system’shigh-pressure pipe. Its contacts are normally
closed, opening when the system reaches the
specified pressure - on receiving this signal,
the ECU increases the idle speed, to
compensate for the additional load on the
engine.
Exhaust gas pressure differential
sensor
11This component measures the difference
in pressure of the exhaust gases across a
venturi (restriction) in the Exhaust Gas
Recirculation (EGR) system’s pipe, and sends
the ECU a voltage signal corresponding to the
pressure difference.
Oxygen sensor
12The oxygen sensor in the exhaust system
provides the ECU with constant feedback -
“closed-loop” control - which enables it to
adjust the mixture to provide the best possible
conditions for the catalytic converter to
operate.
13The sensor has a built-in heating element
which is controlled by the ECU, in order to
bring the sensor’s tip to an efficient operating
temperature as rapidly as possible. The
sensor’s tip is sensitive to oxygen, and sends
the ECU a varying voltage depending on the
amount of oxygen in the exhaust gases. If the
intake air/fuel mixture is too rich, the exhaust
gases are low in oxygen, so the sensor sends
a low-voltage signal, the voltage rising as the
mixture weakens and the amount of oxygen in
the exhaust gases rises. Peak conversion
efficiency of all major pollutants occurs if the
intake air/fuel mixture is maintained at the
chemically-correct ratio for the complete
combustion of petrol, of 14.7 parts (by weight)
of air to 1 part of fuel (the “stoichiometric”
ratio). The sensor output voltage alters sharply
around this point, the ECU using the signal
change as a reference point, and correcting
the air/fuel mixture by altering the fuel injector
pulse width.
Air conditioning system
14Two pressure-operated switches and the
compressor clutch solenoid are connected to
the ECU, to enable it to determine how the
system is operating. The ECU can increase
idle speed or switch off the system, as
necessary, so that normal vehicle operation
and driveability are not impaired. See Chapter
3 for further details, but note that diagnosis
and repair should be left to a dealer service
department or air conditioning specialist.
Automatic transmission
15In addition to the driver’s controls, the
transmission has a speed sensor, a fluid
temperature sensor (built into the solenoid
valve unit), and a selector lever position
sensor. All of these are connected to the ECU,
to enable it to control the transmission
through the solenoid valve unit. See Part B of
Chapter 7 for further details.
Testing
ECU (Electronic Control Unit)
16 Do notattempt to “test” the ECU with any
kind of equipment. If it is thought to be faulty,
take the vehicle to a Ford dealer for the entire
electronic control system to be checked using
the proper diagnostic equipment. Only if all
other possibilities have been eliminated should
the ECU be considered at fault, and replaced.
Air mass meter
17Testing of this component is beyond the
scope of the DIY mechanic, and should be left
to a Ford dealer.
Crankshaft speed/position sensor
18Unplug the electrical connector from the
sensor.
19Using an ohmmeter, measure the
resistance between the sensor terminals.
Compare this reading to the one listed in the
Specifications Section at the beginning of this
Chapter. If the indicated resistance is not
within the specified range, renew the sensor.
20Plug in the sensor’s electrical connector
on completion.
Camshaft position sensor
21The procedure is as described in
paragraphs 18 to 20 above.
Coolant temperature sensor
22Refer to Chapter 3.
Intake air temperature sensor
23Unplug the electrical connector from the
sensor.
24Using an ohmmeter, measure the
resistance between the sensor terminals.
Depending on the temperature of the sensor
tip, the resistance measured will vary, but it
should be within the broad limits given in the
Specifications Section of this Chapter. If the
sensor’s temperature is varied - by placing it
in a freezer for a while, or by warming it gently
- its resistance should alter accordingly.
25If the results obtained show the sensor to
be faulty, renew it.
Throttle potentiometer
26Remove the plenum chamber (see
Chapter 4) and unplug the potentiometer’s
electrical connector.
27Using an ohmmeter, measure the
resistance between the unit’s terminals - first
between the centre terminal and one of the
outer two, then from the centre to the
remaining outer terminal. The resistance
should be within the limits given in the
Specifications Section of this Chapter, and
should alter smoothlyas the throttle valve is
moved from the fully-closed (idle speed)
position to fully open and back again.
28If the resistance measured is significantly
different from the specified value, if there are
any breaks in continuity, or if the reading
fluctuates erratically as the throttle is
operated, the potentiometer is faulty, and
must be renewed.
Emissions control systems 6•11
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Vehicle speed sensor
29Testing of this component is beyond the
scope of the DIY mechanic, and should be left
to a Ford dealer.
Power steering pressure switch
30Unplug the electrical connector from the
sensor.
31Using an ohmmeter, measure the
resistance between the switch terminals. With
the engine switched off, or idling with the
roadwheels in the straight-ahead position,
little or no resistance should be measured.
With the engine running and the steering on
full-lock, the pressure increase in the system
should open the switch contacts, so that
infinite resistance is now measured.
32If the results obtained show the switch to
be faulty, renew it.
Exhaust gas pressure differential
sensor
33Testing of this component is beyond the
scope of the DIY mechanic, and should be left
to a Ford dealer.
Oxygen sensor
34Testing of this component can be done
only by attaching special diagnostic
equipment to the sensor wiring, and checking
that the voltage varies from low to high values
when the engine is running; do notattempt to
“test” any part of the system with anything
other than the correct test equipment. This is
beyond the scope of the DIY mechanic, and
should be left to a Ford dealer.
Removal and refitting
General
35Before disconnecting any of these
components, always disconnect the power by
uncoupling the battery terminals, negative
(earth) lead first - see Section 1 of Chapter 5.
ECU (Electronic Control Unit)
Note:The ECU is fragile. Take care not to
drop it or subject it to any other kind of
impact, and do not subject it to extremes of
temperature, or allow it to get wet.
36Carefully prise the power steering fluid
reservoir upwards out of its clip on the
suspension mounting. Unscrew the ECU
connector’s retaining bolt, and unplug the
connector (see illustrations).
37Working in the passenger compartment,
unscrew the retaining bolt and withdraw the
mounting bracket (see illustration).
38Lifting the ECU to release it from the
bulkhead carrier bracket, withdraw the unit
(see illustration).
39Refitting is the reverse of the removal
procedure. Whenever the ECU (or battery) is
disconnected, the information relating to idle
speed control and other operating values will
be lost from its memory until the unit has re-
programmed itself; until then, there may be
surging, hesitation, erratic idle and a
generally-inferior level of performance. To
allow the ECU to re-learn these values, start
the engine and run it as close to idle speed as
possible until it reaches its normal operatingtemperature, then run it for approximately two
minutes at 1200 rpm. Next, drive the vehicle
as far as necessary - approximately 5 miles of
varied driving conditions is usually sufficient -
to complete the re-learning process.
Air mass meter
40Releasing its wire clip, unplug the meter’s
electrical connector (see illustration).
41Release the clips and lift the air cleaner
cover, then release the two smaller clips and
detach the meter from the cover (see
illustration).
42Slacken the clamp securing the meter to
the resonator hose, and withdraw the meter.
43Refitting is the reverse of the removal
procedure. Ensure that the meter and air
cleaner cover are seated correctly and securely
fastened, so that there are no air leaks.
Crankshaft speed/position sensor
44Refer to Chapter 5.
Camshaft position sensor
45Remove the air mass meter and resonator
(refer to Chapter 4) to gain access to the
sensor (see illustration). Release the fuel
feed and return hoses from their clip.
46Releasing its wire clip, unplug the
sensor’s electrical connector. Remove the
retaining screw, and withdraw the sensor from
the cylinder head; be prepared for slight oil
loss.
47Refitting is the reverse of the removal
procedure, noting the following points:
6•12 Emissions control systems
4.36A Unclip and lift power steering fluid
reservoir - take care not to spill fluid . . .4.36B . . . unscrew bolt (arrowed) to
release ECU’s electrical connector4.37 Unscrew retaining bolt and withdraw
ECU’s mounting bracket . . .
4.40 Unplugging the air mass meter’s
electrical connector . . .4.38 . . . then lift ECU to disengage it, and
withdraw it4.41 . . . release clips to separate meter
from air cleaner cover
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