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Diagnosis system - general information
Emissions control systems / Diagnosis system - general information


General
The various components of the fuel, ignition and emissions control systems (not forgetting the same ECUs 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 systems 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 vehicles 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.

1 The 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.

2 If 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.

3 Open 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.) 4 Referring 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.

5 Next 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 carelesslyrefitted components, or melted by being forced into contact with hot engine castings, coolant or EGR pipes, etc. In almost all cases, damage of this sort is caused in the first instance by incorrect routing on reassembly after previous work has been carried out (see the note at the beginning of this sub-Section).

6 Obviously wires can break or short together inside the insulation so that no visible evidence betrays the fault, but this usually only occurs where the wiring loom has been incorrectly routed so that it is stretched taut or kinked sharply; either of these conditions should be obvious on even a casual inspection. If this is thought to have happened and the fault proves elusive, the suspect section of wiring should be checked very carefully during the more detailed checks which follow.

7 Depending on the extent of the problem, damaged wiring may be repaired by rejoining the break or splicing-in a new length of wire, using solder to ensure a good connection, and remaking the insulation with adhesive insulating tape or heat-shrink tubing, as desired. If the damage is extensive, given the implications for the vehicles future reliability, the best long-term answer may well be to renew that entire section of the loom, however expensive this may appear.

8 When the actual damage has been repaired, ensure that the wiring loom is rerouted correctly, so that it is clear of other components, is not stretched or kinked, and is secured out of harms way using the plastic clips, guides and ties provided.

9 Check all electrical connectors, ensuring that they are clean, securely fastened, and that each is locked by its plastic tabs or wire clip, as appropriate. If any connector shows external signs of corrosion (accumulations of white or green deposits, or streaks of rust), or if any is thought to be dirty, it must be unplugged and cleaned using electrical contact cleaner. If the connector pins are severely corroded, the connector must be renewed; note that this may mean the renewal of that entire section of the loom - see your local Ford dealer for details.

10 If the cleaner completely removes the corrosion to leave the connector in a satisfactory condition, it would be wise to pack the connector with a suitable material which will exclude dirt and moisture, and prevent the corrosion from occurring again; a Ford dealer may be able to recommend a suitable product. Note: The systems connectors use gold-plated pins, which must not be mixed with the older tin-plated types (readily identifiable from the different colour) if a component is renewed, nor must the lithium grease previously used to protect tin-plated pins be used on gold-plated connectors.

11 Following the accompanying schematic diagram, and working methodically around the engine compartment, check carefully that all vacuum hoses and pipes are securely fastened and correctly routed, with no signs of cracks, splits or deterioration to cause air leaks, or of hoses that are trapped, kinked, or bent sharply enough to restrict air flow (see illustrations). Check with particular care at all connections and sharp bends, and renew any damaged or deformed lengths of hose.

3.11A Vacuum hose routing schematic diagram
3.11A Vacuum hose routing schematic diagram

3.11B Installation of vacuum hoses in engine compartment
3.11B Installation of vacuum hoses in engine compartment

12 Working from the fuel tank, via the filter, to the fuel rail (and including the feed and return), check the fuel lines, and renew any that are found to be leaking, trapped or kinked.

13 Check that the accelerator cable is correctly secured and adjusted; renew the cable if there is any doubt about its condition, or if it appears to be stiff or jerky in operation.

Refer to the relevant Sections of Chapter 4 for further information, if required.

14 If there is any doubt about the operation of the throttle, remove the plenum chamber from the throttle housing, and check that the throttle valve moves smoothly and easily from the fully-closed to the fully-open position and 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).

15 Unclip 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 lefthand 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.

16 Start 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.

17 Working 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.

18 Similarly, 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 faulty section of the system, as necessary, to seal the leak.

19 It 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 engines 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.

20 Switch 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.

21 The 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
22 As 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 selfdiagnosis 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.

23 In their basic form, fault code readers are simply hand-held electronic devices, which take data stored within an ECUs 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.

24 Ford 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.

25 Because of the variations in the design of fault code readers, it is not possible to give exact details of the sequence of tests; the manufacturers 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.

26 The 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 connectors output terminal, pin 17. Have a pen and paper ready to write down the codes displayed.

3.26 Location and terminal identification of engine management system
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

27 Set 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 connectors input terminal, pin 48. Be very careful to ensure that you earth the correct terminal - 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 readout.

28 The 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.

29 Next the tester will display code 010 (now acting as a separator), followed by the codes for any faults stored in the ECUs memory; if no faults were stored, code 111 will be displayed.

30 When 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 ECUs memory at the end of the test procedure when any faults have been rectified.

31 The 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.

32 If 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.

33 If 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.

34 Any 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.

35 When 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.

36 As 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 ECUs 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 ECUs 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.

37 Given overleaf are the possible codes, their meanings, and where relevant, the action to be taken as a result of a code being displayed.

Ignition timing and base idle speed check
Note: The following procedure is a check only, essentially of the ECU. Both the ignition timing and the base idle speed are controlled by the ECU. The ignition timing is not adjustable at all; the base idle speed is set in production, and should not be altered.

38 If the fault code read-out (with any checks resulting from it) has not eliminated the fault, the next step is to check the ECUs control of the ignition timing and the base idle speed.

This task requires the use of a Ford STAR tester (a proprietary fault code reader can be used only if it is capable of inducing the ECU to enter its Service Adjustment Programme), coupled with an accurate tachometer and a good-quality timing light. Without this equipment, the task is not possible; the vehicle must be taken to a Ford dealer for attention.

39 To make the check, apply the handbrake, switch off the air conditioning (where fitted) and any other electrical loads (lights, heated rear window, etc), then select neutral (manual transmission) or the P position (automatic transmission). Start the engine, and warm it up to normal operating temperature. The radiator electric cooling fan must be running continuously while the check is made; this should be activated by the ECU, when prompted by the tester. Switch off the engine, and connect the test equipment as directed by the manufacturer - refer to paragraph 26 above for details of STAR tester connection.

40 Raise and support the front of the vehicle securely, and remove the auxiliary drivebelt cover (see Chapter 1). Emphasise the two pairs of notches in the inner and outer rims of the crankshaft pulley, using white paint. Note that an ignition timing reference mark is not provided on the pulley - in the normal direction of crankshaft rotation (clockwise, seen from the right-hand side of the vehicle) the first pair of notches are irrelevant to the vehicles covered in this manual, while the second pair indicate Top Dead Centre (TDC) when aligned with the rear edge of the raised mark on the sump; when checking the ignition timing, therefore, the (rear edge of the) sump mark should appear just before the TDC notches (see Part A of Chapter 2, Section 4, for further information if required).

41 Start the engine and allow it to idle. Work through the engine-running test procedure until the ECU enters its Service Adjustment Programme - see paragraph 35 above.

42 Use the timing light to check that the timing marks appear approximately as outlined above at idle speed. Do not spend too much time on this check; if the timing appears to be incorrect, the system may have a fault, and a full system test must be carried out (see below) to establish its cause.

43 Using the tachometer, check that the base idle speed is as given in the Specifications Section of Chapter 4.

44 If the recorded speed differs significantly from the specified value, check for air leaks, as described in the preliminary checks (paragraphs 15 to 18 above), or any other faults which might cause the discrepancy.

45 The base idle speed is set in production by means of an air bypass screw (located in the front right-hand corner of the throttle housing) which controls the amount of air that is allowed to pass through a bypass passage, past the throttle valve when it is fully closed in the idle position; the screw is then sealed with a white tamperproof plug (see illustration). In service, the idle speed is controlled by the ECU, which has the ability to compensate for engine wear, build-up of dirt in the throttle housing, and other factors which might require changes in idle speed. The air bypass screw setting should not, therefore, be altered. If any alterations are made, a blue tamperproof plug must be fitted, and the engine should be allowed to idle for at least five minutes on completion, so that the ECU can re-learn its idle values.

3.45 Throttle housing air bypass screw is sealed on production with a white
3.45 Throttle housing air bypass screw is sealed on production with a white tamperproof plug (arrowed)

46 When both checks have been made and the Service Adjustment Programme is completed, follow the tester instructions to return to the fault code read-out, and establish whether the fault has been cured or not.

Basic check of ignition system 47 If the checks so far have not eliminated the fault, the next step is to carry out a basic check of the ignition system components, 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.

Basic check of fuel system 48 If the checks so far have not eliminated the fault, the next step is to carry out a basic check of the fuel system components.

49 Assuming that the preliminary checks have established that the fuel pump is operating correctly, that the fuel filter is unlikely to be blocked, and also that there are no leaks in the system, the next step is to check the fuel pressure (see Chapter 4). If this is correct, check the injectors (see Chapter 4) and the Positive Crankcase Ventilation system (see Chapter 1).

System test
50 The final element of the Ford testing procedure is to carry out a system test, using a break-out box - this is a device that is connected between the ECU and its electrical connector, so that the individual circuits indicated by the fault code read-out can be tested while connected to the system, if necessary with the engine running. In the case of many of the systems components, this enables their output voltages to be measured - a more accurate means of testing.

51 In addition to the break-out box and the adaptors required to connect it, several items of specialist equipment are needed to complete these tests. This puts them quite beyond the scope of many smaller dealers, let alone the DIY owner; the vehicle should be taken to a Ford dealer for attention.


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