Petrol Engine Management - PDF

Petrol engine - management Conditions of Use of Training and Technical Information: In consideration of Renault UK limited disclosing to you the information as defined below you agree to comply with the following - in respect of any and all technical and training documentation (including but not l...

Petrol engine - management Conditions of Use of Training and Technical Information: In consideration of Renault UK limited disclosing to you the information as defined below you agree to comply with the following - in respect of any and all technical and training documentation (including but not limited to drawings, wiring diagrams, repair manuals, discs, documents, files, videos, emails or other correspondence) ’the information’-: 1-The information is only to be used by specialists in the field of motor vehicle repair and maintenance. The information may not be sufficient on its own to effect repairs and maintenance of RENAULT vehicles. Therefore you must ensure that you have all the necessary training, knowlegde, documents, skills and equipment to make safe and proper repairs and maintenance of RENAULT vehicles and products. 2-The information is subject to change without prior notice. You must therefore ensure you have the most up to date information available. 3-You acknowledge and agree that you are responsible for all repairs and main- tenance services and that you agree to indemnify RENAULT UK limited against all claims, costs, fees interest and expenses bought against RENAULT as a di- rect or indirect result of your acts or omissions in relying upon the information. Nothing shall exclude RENAULT’s liability for death or personal injury caused by RENAULT’s negligence. 4-Whilst we make every reasonable effort to ensure that the information is up to date and accurate, RENAULT hereby excludes to the greatest extent permisible by law liability to the user of the information. 5-You are not permitted in anyway to copy, sell, hire, lend, lease or otherwhise dispose of the information in any way. You are not permitted to pass the information to any third party without the prior written permission of RENAULT UK limited. 6-The information is the property of RENAULT UK limited. You acknowledge that failure to comply with the above is a serious breach of confidentiality for which damages would not be a sufficient remedy to RENAULT UK limited. 7-You must destroy the information in a confidential manner when you have fin- ished with it or when the agreement for use terminates whichever is the earlier. 1 2 CONTENTS Introduction 4 Fuel supply 6 Ignition 24 Fuel injection 38 Depollution 81 Analysis of the exhaust gases 96 Fault finding procedure 105 Questionnaire 110 3  INTRODUCTION Petrol engine checking/management 5 4  Introduction Petrol engine checking/management NOTE Programs and defect modes are shown as an example in this document. This information does not apply to all vehicles. It is essential to refer to the reference material corresponding to the vehicle before any procedure. 5  FUEL SUPPLY Combustion 7 Richness and the lambda value 8 Injection types 9 Indirect injection supply circuit 11 Direct injection supply circuit 19 Cleanliness instructions. 23 The "fuel circuit" function conformity check 23 6  Fuel supply Combustion Combustion is a reaction between a combustive agent and a fuel, used to produce energy. The combustive agent The combustive agent used in an engine is ambient air. Air consists of the following gases: – 79% nitrogen, – 20% oxygen, – The remaining percentage comprises rare gases. The fuel The fuel is a mixture of hydrocarbons (HC). Hydrocarbons consist of hydro- gen and carbon. The octane rating determines the ex- tent of the ability of the fuel to self-ignite (figure 1). Figure 1. The octane rating is a characteristic representing the quality of the fuel. NOTE The manufacturer’s recommendations should be observed. There are two main types of fuel: leaded petrol and unleaded petrol. The gas mixture The burnt mixture must satisfy three requirements to enable combustion to be as complete as possible. 7 Fuel supply 1. The air-fuel mixture must be gaseous. The injector spray is used to transform the petrol to its gaseous state. 2. The air-fuel mixture must be homogenous. The homogeneity of the mixture influences the speed and quality of com- bustion. 3. The air-fuel mixture must be proportional. The ideal quantity should correspond to a mixture of one gram of fuel for 14.8 grams of air. Richness and the lambda value Richness is the ratio between the actual proportions and the ideal proportions. For an ideal quantity, the richness is equal to 1 and the lambda is also equal to 1 (figure 2). Figure 2. The richness and lambda represent the quantity of the mixture. When the mixture contains more fuel, the richness increases: the mixture is rich and the lambda rating is below 1. When the mixture contains less fuel, the richness decreases: the mixture is lean and the lambda rating is greater than 1. The lambda value is affected inversely to the richness. 8  Fuel supply The output and power proportions Among all the possible mixtures, only one range of mixtures is used depending on the operating phase (figure 3). Figure 3. The output and power proportions. Efficiency proportions equate to a lean mixture of 1 for every 18. These economic proportions are used at medium engine speeds. Power proportions equate to a rich mixture of 1 for every 12. These proportions are used during power requests. Enrichment programming is also applied in the following situations: – when idling, to compensate for the cylinders not being properly filled, – when cold starting, to compensate for condensation of the petrol in the mixture. Injection types There are two types of injection: monopoint injection system and multipoint injec- tion system (figure 4). A monopoint injection system is comprised of a single injector (1). This injector is located upstream of the throttle valve. A multipoint injection system is made up of one injector per cylinder (2). 9 Fuel supply Figure 4. Injection types. On multipoint injection systems, there are three injection methods: simultaneous injection, semi-sequential injection and sequential injection. With simultaneous injection, all the injectors are activated at the same time. With semi-sequential injection, the injectors are activated in twos. In sequential injection, each injector is activated independently. The last difference is the location where the fuel is injected (figure 5). Figure 5. Indirect and direct injection systems. With an indirect injection system , fuel is injected just before the inlet valve (1). On a direct injection system, the fuel is injected directly into the combustion chamber (2). 10  Fuel supply Indirect injection supply circuit An indirect injection fuel supply system (figure 6) is made up of a low pressure supply circuit including the following components: – a reservoir (1), – a fuel pump (2), – a filter (3), – a regulator (4), – a rail (5), – injectors (6). Figure 6. The composition of an indirect injection supply circuit. 11 Fuel supply The fuel tank Antipollution legislation has prohibited the direct release of air from the fuel tank and imposed certain devices (figure 7). The over filling prevention valve prevents fuel overflow. The ball valve prevents petrol backflow into the filler neck. The excess pressure/underpressure valve is activated if the petrol vapour recirculation circuit is blocked. The anti-leak valve prevents the tank from emptying if the vehicle rolls over. Figure 7. The various safety equipment. The fuel pump The role of the fuel pump is to supply a flow of fuel under pressure to the injectors. The pump is driven by an electric motor (figure 8). 12  Fuel supply Figure 8. The electric fuel pump. A safety valve (1) opens if the pressure inside the pump becomes too high. At the output, an anti-return valve (2) maintains the petrol pressure in the circuit to prevent the circuit depriming when the engine stops. The pump is attached under the vehicle chassis or immersed in the fuel tank, usu- ally on the same mounting as the gauge (figure 10). Fuel pump check ► Checking the fuel flow Measure the fuel pressure using a graduated measuring cylinder. Note. If necessary, measure the pump power supply (low voltage or intensity = reduction in flow). Programming in the event of an impact In the event of an impact, the fuel pump supply is cut off by the multiplex network. The airbag computer sends the "impact" signal to the injection computer, which cuts off the fuel pump supply. Multiplex vehicle: if an impact is stored in the injection computer, switch off the ignition for 10 seconds, then turn the ignition back on again to enable the engine to start. Then clear the faults. Non multiplex vehicle with inertia switch: Just press the inertia switch to reposition the ball on its seat. 13 Fuel supply The fuel filter The role of the filter is to prevent impurities that could damage the sensitive parts in the circuit and harm the operation of the injectors. The filter is immersed in the fuel tank or located under the vehicle (figures 9 and 10). Figure 9. This type of filter is located under the Figure 10. This type of filter is immersed in the vehicle. fuel tank. Checking the fuel filter ► Checking the filter The method for checking the supply pressure and pump flow is used to carry out fault finding on the pump/filter/regulator assembly. Note. It is essential to refer to the vehicle Warranty and Servicing booklet to find out how frequently the fuel filter must be replaced. 14  Fuel supply The injector rail The role of the injector rail is to distrib- ute the fuel to the injectors and to pro- vide the link to the supply circuit. The rail may be fitted with a pulsation damper (figure 11). Figure 11. The injection rail. The injectors The injector (figure 12) behaves like a solenoid valve (open circuit/closed cir- cuit). The injector opening time de- pends on the computer control time. Figure 12. The indirect injector. 15 Fuel supply Checking the injectors ► Checks with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards, – absence of misfiring. ► Visual checks: – cleanliness and condition of the injectors, – condition of the connections, – injector sealing. ► Multimeter checks: – presence of + 12 volts on each injector (ignition on), – resistance and insulation of injectors. ► Oscilloscope check: – injector control signal (the check can be made by comparison between signals). ► Gas analyser check: – antipollution conformity. Note. A conformity check carried out using the CLIP fault finding tool is used to take readings of misfirings on the faulty cylinder or cylinders. The indirect injection control signal Reading the injector signal (figure 13), using an oscilloscope (or curve tracer), can show, for example, a seized injec- tor. An injector can have mechanical faults or interference resistance on the elec- trical supply, that may change the elec- trical control signal. Figure 13. The signal matches an injector. The gas analyser associated with the CLIP fault finding tool can be used to show whether an injector is malfunctioning (such as a leaky injector). 16  Fuel supply THE CONFORMITY CHECK FOR EACH SIGNAL CAN BE CARRIED OUT BY COMPARISON OF SIGNALS BETWEEN CYLINDERS. The pressure regulator (variable pressure) On multipoint systems, the air pressure at the nose of the injector varies according to the load. The role of the fuel pressure regulator (figure 14) is to control the return flow to the tank, in order to maintain the correct fuel pressure. The pressure in the injector rail is cor- rected according to the vacuum in the inlet manifold, in order to make the in- jectors operate at a constant pressure. The injection output therefore depends only on the opening time of the injector. Figure 14. The variable pressure regulator. The variable pressure regulator is located on the injector rail. The pressure regulator (constant pressure) On the latest vehicles, the petrol supply pressure is no longer controlled by the manifold pressure. The petrol pressure is constant. 17 Fuel supply With a constant pressure regulator (fig- ure 15), electronic management adapts the injection duration according to the pressure in the inlet manifold. The constant pressure regulator is im- mersed in the tank. Figure 15. The constant pressure regulator. Checking the pressure regulator ► Checking the pressure: – carry out a fuel pressure measurement using a pressure gauge fitted on a "T" piece, – with the engine running, the pressure should be correct and constant. When the engine stops, the pressure should not drop immediately. Note. On some engines fitted with a variable pressure regulator, it is necessary to apply a vacuum to the pressure regulator using a vacuum pump. 18  Fuel supply Direct injection supply circuit A direct injection fuel supply system comprises two circuits: – a low pressure supply circuit, – a high pressure supply circuit, The low pressure circuit The low-pressure circuit is the same as an indirect injection system fuel supply circuit. The low pressure circuit (figure 16) sup- plies the high pressure pump with a constant pressure. Figure 16. The low high pressure supply circuit. The high pressure circuit The high pressure circuit (figure 17) is made up of the following components: – a high-pressure pump (1), – injectors (2), – an injector rail (3), – a pressure sensor (4), – a pressure regulator (5). Figure 17. The high pressure supply circuit. 19 Fuel supply The high pressure pump The high pressure pump (figure 18) is mechanically driven by the inlet camshaft and supplies the fuel rail un- der a pressure of approximately 100 bar. Figure 18. The high pressure pump. The injectors High-pressure injectors (figure 19) are specific but operate on the same prin- ciple as conventional injectors. These injectors are designed to be leaktight at high pressures and to be resistant to the heat from the combus- tion chamber. Figure 19. The high pressure injector. NOTE The high-pressure injector power supply may reach 70 volts. The pressure regulator A direct injection system pressure regulator is a solenoid valve controlled by the computer (figure 20). 20  Fuel supply Figure 20. The pressure regulation loop. This solenoid valve can manage the rail pressure by controlling a fuel leak towards the low-pressure circuit. The pressure sensor The pressure sensor transmits the "fuel pressure on the rail" signal to the injec- tion computer. The computer can thereby adjust the pressure regulator control to obtain the desired pressure. The pressure sensor is fitted on the injector rail. Checking the pressure regulator ► Checking the flow and pressure: – check that there are no leaks, – establish dialogue with the injection computer, – check the pressure conformity. Note. On a high pressure supply system, checks are carried out using the CLIP fault finding tool only. IMPORTANT It is forbidden to connect a pressure gauge to measure the high pressure. This can be read using the CLIP fault finding tool in "States and Parame- ters". Before any procedure is carried out on the high pressure circuit, check that the pressure is below 5 bar using the CLIP fault finding tool. 21 Fuel supply Defect mode programming Whatever the regulator fault, the computer adapts the injection duration according to the fuel pressure supplied by the sensor. FAULTY COMPONENT DEFECT MODE Low pressure in the rail (the regulator The pressure in the rail is low but sufficient is not supplied) to enable the engine to run. The computer switches on a fault warning Too high pressure in the rail light then stops the engine. Cleanliness instructions. The fuel supply systems are sensitive to impurities. Contamination by impurities may lead to a component sticking or leaking from its seals. The cleanliness principles must be applied from the fuel filter to the injectors. The cleanliness instructions are to be found in the technical reference material. IMPORTANT Observe the cleanliness advice when working on the fuel supply circuit. 22  Fuel supply The "fuel circuit" function conformity check In the context of a "correct operation check", the conformity check is an essential stage when verifying a computer or one of its sub- functions. The conformity check, in this context, is carried out using the CLIP fault finding tool and should be carried out in the following order: 1. Check that no fault has been declared. 2. Select the basic functions. 3. Check that the target programming has been carried out. 4. Select the main associated states and parameters to be checked. 5. Check the conformity of each signal noted in the application conditions speci- fied (engine stopped, ignition on and warm engine, at idling speed). NOTE When looking for faults (complete fault finding procedure) where it needs to be determined which component is faulty, the check should extend to all the parameters that interact with the faulty system. Other checks ► Visual checks: – mounting, appearance and sealing of the fuel tank, – the condition, mounting, appearance and sealing (absence of leaks and odours) of the pipes and unions (including the fuel return pipes), – the mounting and sealing of the injector rail and the injectors, – the condition and appearance of the flap and filler neck, – the condition and appearance of the fuel vapour rebreathing circuit up to the inlet manifold, – the mounting, appearance and correct path of the electrical wiring and connectors. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. 23  IGNITION Principles of combustion. 25 Ignition circuits 26 The "Ignition" function and advance programs 29 Faults linked to the ignition 32 "Anti-pinking" function 35 The "Ignition" function conformity check 36 24  Ignition Principles of combustion. Combustion converts the air/petrol mixture into calorific energy. Increasing the heat raises the pressure in the combustion chamber. This pressure increase moves the piston. The role of ignition The role of ignition is to initiate combus- tion of the air/petrol mixture at the most favourable moment (figure 21). Engine combustion occurs in two phases: initiation and flame front prop- agation. The combustion of the mixture is not immediate. There are around 2 mil- liseconds between initiation and com- plete combustion. Figure 21. Ignition of the mixture. The ignition advance If combustion is initiated at TDC (Top Dead Centre), the pressure caused by com- bustion is at its maximum after the piston has already gone downwards. The torque produced is low. If, on the other hand, ignition comes before TDC, combustion will be complete at TDC. The torque produced will be greater. Combustion needs to be initiated before TDC to achieve greater efficiency. Ignition before TDC is known as "ignition advance". 25 Ignition Ignition circuits An ignition circuit (figure 22) is made up of the following components: – a switch (1), – a coil made of two windings (2), – a spark plug (3). The switch can be mechanically acti- vated, controlled by an MPA (ignition power module) or controlled by a com- puter. Figure 22. Ignition basic circuit. Ignition system configuration There are three ignition system configurations: – The ignition is the "distributed" type and has just one coil for all the cylin- ders. – The ignition is said to be "static" and has one coil for one cylinder. – The ignition is said to be "twin-static" and has one coil for two cylinders. Ignition operating principle There are two circuits: the primary and secondary circuit. While the coil is charging, the primary circuit is closed. The opening of the primary circuit generates a high voltage in the secondary circuit of the coil. This high volt- age produces a spark at the spark plug. On recent systems, the injection computer also manages the ignition function. 26  Ignition Ignition with an MPA (ignition power module) On some systems, the primary circuit switch is incorporated in an MPA that controls the intensity of the coil charge (figure 23). The computer sends a control signal to the MPA, which then opens the primary circuit to initiate ignition. Figure 23. The Ignition Power module. Ignition with a twin-static coil On a "twin-static" circuit (figure 24), one coil is allocated to each pair of cylin- ders. At the ignition point, a spark ap- pears on each of the two spark plugs. One spark is used at the end of the compression phase for ignition. The other spark is produced at the end of the exhaust phase. This is said to be "lost". Figure 24. The twin-static coil. 27 Ignition Pencil coil ignition A "pencil coil" system has one coil per cylinder (figure 25). There are two configurations: Firstly, two coils are fitted in se- ries and controlled by the same out- put stage of the computer as with a twin-static coil. In the second case, only one spark is produced sequentially for each cylinder. Figure 25. The pencil coil. Spark plugs Spark plugs work at temperatures between 350 and 850°Celsius (figure 26). The heat range of a spark plug determines its heat extraction capacity. If the spark plug does not radiate enough heat, it will stay hot and may cause pre-ignition (1). If the spark plug extracts too much heat, it will not be at the correct tem- perature and will be choked (2). Figure 26. Observing the heat range of spark plugs. Besides visually checking the condition of the spark plugs, they should be replaced in accordance with the recommended replacement periods. 28  Ignition NOTE A multi-electrode spark plug lasts longer than a single electrode spark plug as the spark changes electrode each time one wears out. It is essential to fit the spark plugs recommended by the manufacturer. The "Ignition" function and advance programs The "Ignition" function produces the spark at the right moment. This function uses the flywheel sensor and coils (figure 27). Figure 27. "Ignition" function components The flywheel sensor is an inductive sensor located opposite a toothed target fitted to the flywheel. The flywheel sensor (figure 28) is used to determine the en- gine rotation speed and the crankshaft position in relation to the top dead centre of the cylinders. Figure 28. The engine flywheel signal. 29 Ignition The ignition program in relation to the flywheel sensor The computer determines the moment of ignition in relation to the flywheel sensor signal and the desired advance. Ignition programming by the camshaft sensor Most vehicles use ignition systems that produce two simultaneous sparks on two cylinders. On some ignition systems, only one spark is produced sequentially for each cylin- der. The information identifying the cylinder requiring ignition is supplied by the camshaft sensor. Advance correction programming The ignition advance may be modified in line with the following parameters: – the inlet manifold pressure, – the coolant temperature – the air temperature. Defect mode programming There is no defect mode programming for the flywheel sensor. FAULTY COMPONENT DEFECT MODE Flywheel sensor No defect mode Manifold pressure sensor Using a default advance value Coolant temperature sensor Using a default advance value Air temperature sensor Using a default advance value Ignition coil No defect mode IMPORTANT Any fault on the flywheel sensor prevents the engine from running. 30  Ignition Faults linked to the ignition Explosive combustion Explosive combustion is instantaneous propagation of the flame front. It is facilitated by too low an octane rating for the engine compression pressure. Self-ignition Self-ignition is the spontaneous combustion of the mixture before the spark ap- pears. It is caused by excessive compression, which raises the temperature of the mixture above the spontaneous ignition threshold. Pre-ignition Pre-ignition is the uncontrolled ignition of the mixture before the spark due to a hot spot. This ignition occurs on contact with a combustion chamber hot spot (sharp edge, too hot spark plug electrode or exhaust valve). IMPORTANT All these combustion faults lead to random combustion. Pinking When two flame fronts meet a shock wave known as pinking is produced. Pinking causes sudden overheating that may melt the spark plug electrodes or the piston crown. Spark plugs During an engine fault finding procedure, the spark plug condition check (figure 29) is a good indicator of the mechanical condition of the engine and may also show malfunctions, mechanical problems etc. 31 Ignition THE CONDITION OF THE SPARK PLUGS MAY REFLECT THE QUALITY OF THE ENGINE COMBUSTION. Normal conditions: light brown or grey deposits. Correct operation of the engine and ignition system, correct heat range. Carbon deposits: black soot deposits. Frequent operation of the engine when cold, ignition retardation, incorrect op- eration of the fuel vapour rebreathing system, compression too low or spark plug too cold, etc. Overheating: white insulation and excessive wear on the elec- trodes. Excessive advance, mixture too lean, heat range too low, spark plug too hot,... Pre ignition: melted electrodes. Pre-ignition, heat range too low, valve not leaktight, etc. Oil clogging: general engine wear (if it affects all the spark plugs). Valve guides not leaktight, worn piston rings, etc. Additive deposits: thick but brittle deposits. Consequences of some additives contained in fuel, all the spark plugs must be replaced. Figure 29. Condition of the spark plugs according to different engine conditions. IMPORTANT A malfunction of one of the components located upstream of the spark plugs can make a fault appear on the spark plugs. 32  Ignition Some faults where spark plugs may be the root cause: The engine does not start (check conformity, condition, adjustment). The engine lacks power. The engine consumes fuel excessively. Idle speed is unstable. There are delays in acceleration, jerking at a stable speed or with light accel- eration. Self ignition (adjustment, conformity or condition of spark plugs). The piston is damaged. NOTE Malfunctioning of one of the spark plugs is usually diagnosed by the OBD system. Ignition curves During a fault finding procedure, an ignition curve reading (figure 30) is a quick way to confirm a fault, to determine the faulty component in a high volt circuit and to direct the fault finding procedure to the ignition. The check carried out with a multimeter may not be enough to carry out fault finding on a faulty coil or spark plug. An "engine running" check is the most efficient way of checking the ignition. The curve tracer or oscilloscope function on the fault finding tool are used to display the curve of the secondary circuit signal and to check that the information received is consistent, under different engine load conditions, from which it will be possible to set up a fault finding procedure. 33 Ignition The oscilloscope shows the following information: – coil charge (1), – ionisation voltage (2), – spark gradient and duration(3). Figure 30. An ignition curve reading. The ionisation voltage corresponds to the voltage required to initiate the spark. The spark gradient is due to the increasing pressure in the cylinder that raises the spark voltage. This information may be used to produce a diagnosis. THE CONFORMITY CHECK FOR EACH SIGNAL CAN BE CARRIED OUT BY COMPARISON OF SIGNALS BETWEEN CYLINDERS. Some factors influencing the ignition curve PRIMING SPARK FACTOR VOLTAGE DURATION Lean mixture ↑ ↓ Significant gaps between electrodes ↑ ↓ High pressure in the cylinder ↑ ↓ High electrical resistance in the high voltage circuit ↑ ↓ NOTE The higher the initiation voltage, the shorter the spark duration. 34  Ignition "Anti-pinking" function The "Anti-pinking" function optimises the ignition advance without adversely af- fecting the engine. This function uses the following components (figure 31): – the pinking sensor, – the flywheel sensor, – the ignition coils. Figure 31. The "Anti-pinking" function components. There are two types of pinking: "non-destructive" pinking which can be heard and affects engine output and "destructive" pinking which is inaudible and can damage the engine. The computer applies different programs according to the pinking detected. The program for correcting "non destructive" pinking cannot be seen using the CLIP fault finding tool. The program for correcting "destructive" pinking can be seen using the CLIP fault finding tool. 35 Ignition Possible causes of pinking The main causes of engine pinking are as follows: – wrong fuel, – wrong spark plugs, – hot air intake (at the inlet), – cylinder head resurfacing, – engine overheating or wear, – oil consumption. Defect mode programming If there is a fault on the pinking sensor, the computer uses a reduced ignition ad- vance to reduce the risk of pinking. FAULTY COMPONENT DEFECT MODE Pinking sensor Using a reduced ignition advance Flywheel sensor No defect mode Ignition coil No defect mode NOTE The pinking sensor and its wiring harness are carried out using the CLIP fault finding tool. The "Ignition" function conformity check In the context of a "correct operation check", the conformity check is an essential stage when verifying a computer or one of its sub- functions. The conformity check, in this context, is carried out using the CLIP fault finding tool and should be carried out in the following order: 1. Check that no fault has been declared. 2. Select the basic functions. 3. Check that the target programming has been carried out. 36  Ignition 4. Select and check the main associated states and parameters. 5. Check the conformity of each signal noted in the application conditions speci- fied (engine stopped, ignition on and warm engine, at idling speed). NOTE When looking for faults (complete fault finding procedure) where it needs to be determined which component is faulty, the check should extend to all the parameters that interact with the faulty system. Other checks ► Checks with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards, – conformity of the fault line on the MPA (Ignition Power Module) command line or coils, – ignition test (only accessible on some types of computer). ► Multimeter checks: – continuity and insulation of wiring harnesses, – resistance of primary and secondary coil circuits, – coil supplies, – command line, – MPA supply (ignition power module). ► Oscilloscope check: – display of the different signals. ► Visual checks: – condition, sealing of the high voltage wiring harnesses (presence of water or dampness), – condition, tightening and correct adjustment of spark plugs, range or references corresponding to the engine, – condition of the ignition coil connectors, – absence of current leaks on pencil coils (split body, intruded part, etc.), – condition of the line between the coils and actuator relay or the UPC. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. 37  FUEL INJECTION The computer 39 Programming - Reprogramming a computer 41 The "Power supply" function 49 The "Fuel supply" function 50 The "Injection" function 52 The "Injection correction" function 55 The "Load control" function 57 The "Idle speed regulation" function 61 The "Camshaft dephaser" function 65 The "Variable inlet" function 68 The "Turbocharging" function 70 The "Injection phasing" function 72 The "Injection cut" function 75 The "Air conditioning" function 77 The "Antipercolation/Coolant Temperature Management" function 79 38  Fuel injection The computer The purpose of engine management is to inject and ignite a precise quantity of petrol in the combustion chamber. This operation must be respond to the driver’s requests, while observing the vari- ous depollution standards. Operating programming The injection computer is connected to several components (figure 32). Figure 32. The injection computer is at the heart of the injection system. 1. The computer receives information from the sensors, controls the actuators and exchanges information with other computers. 2. The computer compares the information received to the programmed values. 3. According to the values received, the computer decides whether to actuate the actuators. 39 Fuel injection Electrical fault programming The injection computer can perform fault finding on electrical faults on the circuits of components attached to it. In the event of a fault, the computer switches on different warning lights ac- cording to the fault level (figure 33) and can use defect programs to compen- sate for the fault. Figure 33. The computer switches on various warning lights. NOTE Refer to the technical documentation for any injection system fault find- ing. 40  Fuel injection Programming - Reprogramming a computer The programming/reprogramming process Electronic system management is carried out by "computers". The computer con- trols the system actuators based on the data it receives. On current vehicles, the injection com- puters (figure 34) may require program- ming or reprogramming. Programming is only carried out when installing a new computer. Reprogramming a computer can be used to resolve an identified problem or update the software. Figure 34. Reprogrammable computer. IMPORTANT Since the immobiliser code programming is permanent, carrying out tests with injection computers borrowed from the parts department which need to be returned is prohibited. 41 Fuel injection Definition of the terms used TERM DESCRIPTION HARDWARE The term HARDWARE refers to the physical parts of a computer. It is made up of the following components: – the unit, – the connections, – the internal electronic components. EEPROM The term EEPROM (Electrically Programmable Read-only Memory) de- scribes the electronic component that constitutes the "memory" part of the computer. It is the EEPROM memory that is written or replace during reprogram- ming procedures on the computer. SOFTWARE Also known as the program, this term refers to the "intelligence" recorded in the computer memory (EEPROM). The computer receives a great deal of data from the various sensors, enabling it to control the various actuators following a predefined logic. Replacing the software avoids having to replace the computer in case of a non-hardware fault. CALIBRATION Calibration is a part of the software that represents the program "set- tings". Calibration includes the threshold values applied in the system management. Examples: – the cooling fans trigger threshold, if the temperature exceeds 105 °C, – idle speed value at 1200 rpm, if the coolant temperature is below 60°C. – the injection recommencement below from 1500 rpm during decelerations, – turbocharging pressure threshold at 0.9 bar, – etc... Replacing the calibration can be used to resolve problems such as en- gine hesitation, stalling, excessively abrupt gear changes with automatic transmission, etc. Downloading is the data transfer phase to the computer memory (EEP- DOWNLOAD- ROM). ING The old software (or calibration) is first deleted before rewriting. 42  Fuel injection When should a computer be programmed/reprogrammed? When a new computer is delivered blank (information on DIALOGYS), it must be programmed (figure 35). This is the case for an injection system common to several engines but with different calibrations. Figure 35. Programming/reprogramming tools. During a vehicle’s service life, it is sometimes necessary to replace the content of a computer (software or calibration) to improve its operation or resolve a fault upon RENAULT’s recommendation (Technical Note, Special Technical Operation). How should a computer be reprogrammed? Reprogramming is carried out using the diagnostic tool. There are two ways of doing this: CD-Rom The diagnostic tool finds the corre- sponding software for the computer on the reprogramming CD-ROM (figure 36). The CD-ROM is updated monthly and contains the existing list of software and calibrations. Figure 36. CD-Rom mode. 43 Fuel injection Remote connection Accessing RENAULT.net (figure 37) provides direct access to the database containing the software and calibrations without using a CD-ROM. RENAULT.NET has the advantage of being up- dated in real time and is therefore preferable. Figure 37. RENAULT.NET mode. This service is known as NRE (New Electronic Repair). Outline of the procedure The write procedure is automatic. The CLIP diagnostic tool uses the data supplied by the operator in order to choose the suitable software or calibration (from the CD-ROM or the on-line database). When downloading is complete, the information on the new software version or calibration version is displayed. IMPORTANT Specific procedures may be required before and after reprogramming. Follow the indications displayed on the screen and in the technical ref- erence material carefully. Stage 1: Identification The "Reprogramming" menu is accessed by identifying the vehicle in the con- ventional way (model, type, VIN). After selecting the computer to be reprogrammed from the list offered, you need to choose the reprogramming mode (CD-ROM or RENAULT.NET). After the Repair Order is entered and according to the VIN number recorded, the CLIP fault finding tool finds the appropriate software or calibration from the CD-ROM or the server RENAULT.net. 44  Fuel injection IMPORTANT An error message may appear during the identification operation. An error message means that the data supplied (VIN number) does not enable the fault finding tool to find the suitable software or calibration. The emergency procedure should be adopted to solve the problem. Send the Techline the information on the CLIP fault finding tool’s "computer identification"menu, and the error code (101, 102, 103, etc.). If the code corresponds to an identification problem, the Techline sends a "VTD" (Vehicle Technical Definition) code. This code, to be entered on the CLIP di- agnostic tool, identifies the software suitable for the computer. Stage 2: Traceability "CD-Rom mode" Before beginning downloading, the CLIP fault finding tool displays a "reprogram- ming code". This random code must be given to the codes management service to obtain an "After Sales reprogramming key (or code)" for the operation in progress. This key (or code) is used to establish a reprogramming history for the vehicle. Stage 3: Downloading During this procedure, the content of the computer memory is erased. The new software or calibration is written. It is important not to interrupt the connection between the computer and the fault finding tool during the downloading operation (figure 38). Figure 38. Downloading procedure. 45 Fuel injection Stage 4: End of procedure In order to finalise the reprogramming operation, it may be necessary to carry out special instructions. These are specified on a new screen. Stage 5: New information At the end of downloading and after the operations displayed have been carried out, a screen (warranty screen) resumes the reprogramming procedure. The type of reprogramming is shown on the screen: – TOTAL, for software and calibration replacement. – PARTIAL, for calibration replacement only. This screen also displays the information required for the warranty reimbursement of the procedure (CODECAL). Main points The download operation poses risks for the computer. Indeed, during this proce- dure, when the content has been erased, it is important not to break the connection between the computer and the CLIP fault finding tool during downloading. IMPORTANT If the download procedure is interrupted, the computer may be irretriev- ably damaged. It is essential to follow the instructions in the Technical Note and the in- structions on the screen of the CLIP fault finding tool. The main instructions to be followed are: – maintain the battery voltage (CLIP and vehicle), – keep to the engine temperature threshold (instability of computer compo- nents), – prevent any disconnection of the diagnostic socket. 46  Fuel injection Certain data (programming, injector codes, etc.) are cleared during the operation. It may be useful to save this data on the CLIP diagnostic tool and rewrite it at the end of the operation. Computer signals The CLIP diagnostic tool can find out information on the computer. IDENTIFICATION FRAME CONSULTATION The identification menu is used to identify the computer and its contents. CONTENTS DESCRIPTION The Parts Department part number is the PART or PARTS DEPARTMENT replacement part reference. PART NO. This part no. changes with different reprogrammings. The DIALOGYS screen shows the changes in the part no. The three figure supplier code indicates the computer SUPPLIER supplier (Bosch, Siemens, Sagem, etc.). The VDIAG number indicates the diagnostic version. VDIAG NUMBER It is used to identify the reference material to be used. The program number designates the type of software PROGRAM NUMBER used (EDC16 with or without IMA). The software version specifies the software version present on the vehicle. SOFTWARE VERSION The version changes during a complete repro- gramming procedure. The calibration number specifies the calibration version present on the vehicle. CALIBRATION NUMBER The version changes during a partial repro- gramming procedure. The electronic version indicates the part no. of the physical part of the unit. ELECTRONIC VERSION or It can only change after a computer is replaced. HARD COPY It is a supplier’s part number which cannot be used to order a new part. VIN CODE The VIN code is the vehicle identification number. This information is useful mainly during the emergency procedure (part no., sup- plier code, etc.). It is also used when selecting the technical reference material (VDIAG number). 47 Fuel injection HISTORY AREA CONSULTATION The history area reference screen can be accessed via the "Reprogramming" menu. It shows all the reprogramming procedures carried out on the computer. CONTENTS IDENTIFICATION The Parts Department part number is the PART or PARTS DEPARTMENT replacement part reference. PART NO. This part no. changes with different reprogrammings. The DIALOGYS screen shows the changes in the part no. The VDIAG number indicates the diagnostic version. VDIAG NUMBER It is used to identify the reference material to be used. The three figure supplier code indicates the computer SUPPLIER supplier (Bosch, Siemens, Sagem, etc.). The electronic version indicates the part no. of the physical part of the unit. ELECTRONIC VERSION or It can only change after a computer is replaced. HARD COPY It is a supplier’s part number which cannot be used to order a new part. SOFTWARE or PROGRAM The program number designates the type of software NUMBER used (EDC16 with or without IMA). The software version specifies the software version present on the vehicle. SOFTWARE VERSION The version changes during a complete repro- gramming procedure. The calibration number specifies the calibration version present on the vehicle. CALIBRATION NUMBER The version changes during a partial repro- gramming procedure. The vehicle’s homologation number specifies its values of polluting emissions measured during its certification. HOMOLOGATION NUMBER It is used to check that emissions comply with current standards. PROGRAMMING SITE The reference refers to the location where reprogramming REFERENCE was carried out (factory, after sales workshop, etc.). The number indicates the number of reprogramming REPROGRAMMING NUMBER procedures carried out since the computer was installed. REPROGRAMMING DATE Date for each reprogramming procedure. This marking indicates that a procedure has REGISTRATION MARKING been successful. A successful procedure is indicated by a code (5C). 48  Fuel injection The "Power supply" function Electrical supply The "Power supply" function is used to power the computer and certain actuators when the ignition is switched on. This function uses the following components (figure 39): – the "+ after ignition feed" signal, – the power supply relay. Figure 39. The "Electrical supply" function components. The UPC (Protection and Switching Unit) incorporates the different relays that en- able the injection actuators to operate. NOTE There is no UPC on some vehicles. The relays are located on a fuse board. Defect mode programming There is no defect mode for the "Electrical supply" function. FAULTY COMPONENT DEFECT MODE "+ after ignition" signal The electrical supply relay is not supplied. 49 Fuel injection The "Fuel supply" function Fuel supply The "Fuel supply" function supplies the fuel pump in line with the necessary con- ditions. This function uses the following components (figure 40): – the "+ after ignition feed" signal, – the "engine running" signal, – the "immobiliser" signal, – the "impact" signal, – the fuel pump supply relay. Figure 40. The "Fuel supply" function components. The fuel pump relay The injection computer controls the fuel pump via a relay. The fuel pump supply relay is activated if the ignition is on, the engine is turning and the immobiliser is inactive. In the event of an impact, the airbag computer sends a signal to the injection com- puter, which cuts the fuel supply. On non multiplex vehicles, an inertia switch is used to open the circuit and cut the fuel pump supply in the event of impact. 50  Fuel injection Defect mode programming There is no defect mode for the "Fuel supply" function. FAULTY COMPONENT DEFECT MODE "+ after ignition" signal No defect mode "Engine running" signal No defect mode "Immobiliser" signal No defect mode No defect mode Air bag computer (The fuel supply system is deactivated if the airbag computer is locked.) Fuel pump supply relay No defect mode NOTE Any fault with the input signals will prevent control of the fuel pump supply relay. Checking the UPC and relays ► Checks with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards, – command mode if possible, – UPC conformity. ► Multimeter checks: – supply, continuity and insulation, – resistance of the coil and diodes, if necessary, – resistance of the power circuit. Note. Check the conformity of the diode relays (single or double diode) during a peripherals check of a computer and more particularly after a computer has been destroyed. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. IMPORTANT A faulty diode relay can cause a computer to be destroyed as it no longer plays a protective role. 51 Fuel injection The "Injection" function The "Injection" function is the fundamental function of an injection computer. This function actuates the injectors at the right moment, and for an appropriate length of time. This function uses the following components (figure 41): – the flywheel sensor, – the manifold pressure sensor or air mass flow sensor, – the injectors. Figure 41. "Injection" function components the manifold pressure sensor The manifold pressure sensor is a piezo-resistive sensor. It tells the computer the air pressure in the inlet manifold. This information, combined with the engine speed, enables the computer to deter- mine the quantity of petrol to inject. DIFFERENCE BETWEEN RELATIVE AND ABSOLUTE PRESSURE: Relative pressure: zero pressure corresponds to the atmospheric pressure. Absolute pressure: the reference is absolute zero (corresponds to complete vacuum). RELATIVE PRESSURE + ATMOSPHERIC PRESSURE = ABSOLUTE PRESSURE 52  Fuel injection The air mass flow meter The air mass flow meter is used on certain systems, instead of the manifold pres- sure sensor. This sensor measures the mass of air entering the engine. This information, combined with the engine speed, also enables the computer to determine the quantity of petrol to inject. The injectors Injectors behave like solenoid valves. Supply: The injectors receive a "+ 12 volts" supply via the electrical supply relay or the Protection and Switching Unit. Command: The computer sends an earth to the injectors sequentially to control them. Injection programming 1. The injection computer uses the signals from the flywheel sensor and man- ifold pressure sensor (or the air mass flowmeter) to determine the air mass entering a cylinder. 2. The computer calculates the quantity of petrol required to obtain the appro- priate mixtures. This quantity of petrol corresponds to an injector opening duration. 3. The computer also uses the flywheel sensor to determine when it should open the injector. Defect mode programming The flywheel sensor does not have a defect mode. FAULTY COMPONENT DEFECT MODE Flywheel sensor No defect mode Manifold pressure sensor or air mass Value calculated from the throttle position flowmeter Injectors No defect mode IMPORTANT Any fault on the flywheel sensor prevents the engine from starting. 53 Fuel injection Checking the flywheel sensor, ► Check with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards. ► Multimeter checks: – wiring harness continuity, – sensor resistance and insulation. ► Oscilloscope check: – electrical signal display, – condition of the target. Checking the manifold pressure sensor ► Checks with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards, – consistency between the value read on the CLIP fault finding tool and a vacuum pump. ► Other checks: – condition and appearance of the pneumatic connection (depending on the type of sensor), – condition and appearance of the seal. Checking the air mass flowmeter ► Check with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards. ► Multimeter checks: – wiring harness continuity, – supply, – voltage or output value. ► Other checks: – air flow section, – clogging of the heating element. 54  Fuel injection The "Injection correction" function The "Injection correction" function is used to adapt the injection duration in line with several parameters. This function uses the following components (figure 42): – the manifold pressure sensor, – the coolant temperature sensor, – the air temperature sensor, – the "battery voltage" signal, – the injectors. Figure 42. The "Injection correction" function components. Program for correcting the injection timing The injector opening time is corrected in line with the following parameters: – The computer stores the information provided by the manifold pressure sensor when the ignition is switched on as the atmospheric pressure. If the atmospheric pressure decreases, the injector opening duration de- creases. – The computer uses the coolant temperature information to apply enrich- ment programming when the engine is cold. 55 Fuel injection – The computer uses the air temperature information to correct the calcu- lation of the mass of air entering the cylinder. – The computer uses the battery voltage information to compensate for the influence of the injector power supply on the duration of the actual opening. Defect mode programming There are specific defect mode programs for each sensor in the function. FAULTY COMPONENT DEFECT MODE Manifold pressure sensor (atmospheric The "atmospheric pressure" signal is no pressure) longer taken into account Use of the air temperature when starting Coolant temperature sensor then an arbitrary value Air temperature sensor Use of an arbitrary value "Battery voltage" signal No defect mode Injectors No defect mode 56  Fuel injection The "Load control" function The "Load control" function is used to actuate the throttle opening in line with sev- eral parameters. This function uses the following components (figure 43): – the accelerator pedal position sensor, – the motorised throttle body, – the throttle position sensor, – the "speed limiter/cruise control" signal, – the automatic transmission computer, – the ESP system. Figure 43. The "Load checking" function components. The "pedal" position sensor and "motorised throttle body" The accelerator pedal position sensor is a twin track potentiometer. The motorised throttle valve position sensor uses the same principle. Signal redundancy ensures there consistency. 57 Fuel injection Types of motorised throttle bodies There are two types of motorised throttle body (Figure 44): Figure 44. The two types of motorised throttle body. On the first type, the throttle is actuated by a rotor comprising two magnetic poles (1). The computer powers a winding, which generates a magnetic field and modi- fies the position of the rotor. On the second type, the throttle is activated by a direct current electric motor (2). The computer reverses the supply polarity to open or close the throttle. The injection computer analyses the driver’s request and controls the motorised throttle body to open or close it in accordance with the request. Load control programming The "load control" function uses the following programming (figure 45): 1. The injection computer analyses the driver request via the accelerator pedal position sensor. 2. The computer then actuates the motorised throttle valve to open or close it, according to the request. 3. The throttle position sensor tells the computer the actual throttle opening, enabling it to correct the value. 58  Fuel injection Figure 45. The load control loop. The driver’s request is ignored according to the following program: Priority 1. Torque smoothing request by the automatic transmission computer. Priority 2. Load reduction request by the ESP system Priority 3. Load request by the Speed Limiter/Cruise Control NOTE The Speed Limiter/Cruise Control function is built into the injection com- puter. Defect mode programming The defect mode programming depends on the systems and faults. FAULTY COMPONENT DEFECT MODE Accelerator pedal position sensor Engine maintained at a constant high speed Throttle position sensor Limitation of throttle opening Motorised throttle valve Fast idle speed maintained by a return spring 59 Fuel injection Checking the "pedal" position sensor and "motorised throttle body" ► Check with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards. ► Multimeter checks: – continuity, – supply, – variable output voltage depending on the throttle position, – earth provided by the computer, – resistance and insulation of tracks. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. The same reprogramming procedure for a computer may be required when replacing a motorised throttle body. 60  Fuel injection The "Idle speed regulation" function The "Idle speed regulation" function is used to adjust the air flow required to main- tain the idling speed. This function uses the following components (figure 46): – the flywheel sensor, – the accelerator pedal position sensor or throttle position sensor, – the coolant temperature sensor, – the idle speed regulator. Figure 46. The "Idle speed regulation" function components. The "No load" signal Idle speed regulation is active when the computer receives the "no load" signal. Depending on the systems, this signal can come from the throttle position sensor on wired accelerator systems or from the accelerator pedal on vehicles fitted with a motorised throttle body. 61 Fuel injection The different types of idle speed regulator There are different types of idle speed regulator (figure 47). The single coil valve is a simple solenoid valve bypassing the throttle. The computer powers the valve with a modulated pulsed current (RCO signal). When the supply is off, the single coil valve is returned to a closed position by a return spring. The double coil valve bypasses the throttle. On this valve, one winding actuates the opening of the throttle valve, and the other winding actuates its closure. When the supply is off, the double coil valve is held in an open position by a return spring. Throttle valve activated by a stepping motor. The com- puter powers the stepping motor sequentially to regulate the air supply. When there is no supply, the throttle valve is fixed in its posi- tion. The motorised throttle body. The computer actuates the closure of the throttle to obtain the appropriate air flow. When there is no supply, the motorised throttle valve is held slightly open by a return spring. Figure 47. The different types of idle speed regulator. Operation programming On a system fitted with a motorised throttle body, the computer compares the en- gine speed, from the flywheel sensor with the instruction speed and adjusts the idle speed regulator command. 1. The accelerator pedal position sensor transmits the "no load" signal. Idle speed regulation is activated. 2. The flywheel sensor provides the engine speed signal. 62  Fuel injection 3. The coolant temperature affects the programmed speed. 4. The idle speed regulator control is adjusted to obtain the programmed speed. Other parameters may affect the programmed idling speed. On some systems, the idling instruction speed is increased in the following cases: – battery voltage too low, – too much power-assisted steering pressure, – a gear engaged on a vehicle which is equipped with automatic transmis- sion, – the air conditioning compressor is engaged. Idle speed adaptives The air circuit naturally becomes choked. Recent systems correct this deviation using an electronic adaptive strategy. The computer needs to open the idle speed regulator increasingly to maintain the pro- grammed speed. Here is an example of correction performed by the computer when the air circuit becomes choked. 1. The computer should increase the idle speed regulator opening control. 2. If the idle speed regulator control reaches a certain value, the computer recentres this control by adding a so-called "adaptive" correction. This correction supplements the initial opening control. In the event of an air leak, the phenomenon is reversed. EXCESS AIR: IDLE SPEED RCO VALUE AND ADAPTIVE DECREASE. LACK OF AIR: IDLE SPEED RCO VALUE AND ADAPTIVE INCREASE. 63 Fuel injection IMPORTANT During a fault finding procedure, it is essential to check the conformity of the idle speed and adaptives command values. Defect mode programming The consequences of an idle speed regulator fault depend on the type of regulator. It may lead to an unstable idling speed, fast idling speed or the engine stalling. FAULTY COMPONENT DEFECT MODE "No load" signal Idle speed regulation fault Coolant temperature sensor Can lead to an unsuitable instruction speed Checking the different types of idle speed regulator. ► Check with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards. ► Multimeter checks: – continuity, – supply and insulation of the wiring harness, – winding resistance, – mechanism (seizing), – presence of the "no load" signal (minimum stop). ► Oscilloscope check: – display of the different signals. ► Other check: – air flow choking. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. 64  Fuel injection The "Camshaft dephaser" function The "Camshaft dephaser" function modifies the valve timing diagram. This func- tion uses the following components (figure 48): – the camshaft sensor, – the flywheel sensor, – the camshaft dephaser solenoid valve. Figure 48. The "Camshaft dephaser" function components. The role of the camshaft dephaser is to optimise engine performance by increasing torque at low engine speed and power at high engine speed. At high engine speed, the inlet valve can stay open after Bottom Dead Centre, to increase filling. At low engine speed, the camshaft dephaser closes the inlet valve earlier to pre- vent backflow of fresh inlet gas. Paddle dephaser The paddle dephaser (figure 49) comprises a paddle wheel mounted on the camshaft and a honeycombed cylinder mounted on the camshaft pulley. 65 Fuel injection At low speeds, the solenoid valve allows the oil to flow under pressure which causes the paddle wheel to turn in relation to the cylinder. At high engine speed, the oil supply is cut off. The paddle wheel is returned to its initial position by the engine rotation. Figure 49. Paddle dephaser. NOTE On certain systems, the return to the initial position is achieved by revers- ing the oil supply. Helical tooth dephaser The helical tooth dephaser (figure 50) comprises a spiral screw fitted on the camshaft, a sliding sprocket and a cylinder mounted on the camshaft pulley. Figure 50. The helical tooth dephaser. At low engine speed, the solenoid valve allows a pressurised oil flow. The movement of the sliding sprocket on the screw causes angular dephasing of the camshaft and the pulley. 66  Fuel injection At high engine speed, the oil supply is cut off. The spring returns the sliding sprocket to the left and ends the dephasing. Operation programming Depending on the system, the camshaft dephaser solenoid valve control can either be "full on - full off", or variable. The computer can control camshaft dephasing via the camshaft sensor signal. Defect mode programming There is no defect mode for the flywheel sensor. In the event of a camshaft sensor fault, the "Camshaft dephaser" function is inhibited. FAULTY COMPONENT DEFECT MODE Flywheel sensor No defect mode Camshaft sensor "Camshaft dephaser" function deactivated Camshaft dephaser solenoid valve or Defect engine performances hydraulic circuit. Camshaft phase controller check ► Checks with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards, – conformity of the solenoid valve control value. ► Multimeter checks: – wiring harness continuity, – solenoid valve resistance. ► Other check: – engine valve timing. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. 67 Fuel injection The "Variable inlet" function The "Variable inlet" function optimises the engine torque curve. This function uses the following components (figure 51): – the flywheel sensor, – the variable inlet solenoid valve. Figure 51. The "Variable intake" function components. The variable intake flap On a V6 engine, the gas flow into the inlet manifold is disrupted at low engine speed. To prevent this problem, a variable in- take butterfly valve (figure 52) isolates the two cylinder banks at low speed. At high engine speed, however, the flow is better on a 6 cylinder engine. The two cylinder banks are linked by the butterfly valve. Figure 52. The variable intake flap. 68  Fuel injection Operation programming The computer actuates a variable solenoid valve according to the engine speed. The solenoid valve is used to actuate a pneumatic control opening or closing the butterfly valve. Defect mode programming There is no defect mode for the flywheel sensor. FAULTY COMPONENT DEFECT MODE Flywheel sensor No defect mode Variable solenoid valve No defect mode A seized butterfly valve will impair Variable butterfly valve performance at low or high engine speed. NOTE A fault on the solenoid valve or pneumatic circuit will lock the butterfly valve in the open or closed position. Checking the variable solenoid valve ► Checks with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards, – conformity of the variable solenoid valve control value. ► Multimeter checks: – wiring harness continuity, – solenoid valve resistance. ► Other check: – pneumatic fitting condition. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. 69 Fuel injection The "Turbocharging" function The "Turbocharging" function controls the turbocharging pressure. This function uses the following components (figure 53): – the manifold pressure sensor, – the turbocharging solenoid valve. Figure 53. The "Turbocharging" function components Operation programming 1. The pressure sensor tells the computer the turbocharging pressure in the inlet manifold. 2. The computer actuates the turbocharging solenoid valve using an RCO signal to adjust the turbocharging pressure. 3. The solenoid valve supplies the pneumatic control actuating the turbocharger wastegate valve. 70  Fuel injection Defect mode programming In the event of manifold pressure sensor failure, the computer uses control values limiting the turbocharging pressure. FAULTY COMPONENT DEFECT MODE Using the turbocharging pressure limiting Manifold pressure sensor command values Turbocharging solenoid valve No supply to the pneumatic valve If the wastegate valve is open, the engine will run without turbocharging. Wastegate valve If the wastegate valve is closed, the computer limits the engine performance. Checking the turbocharging solenoid valve ► Checks with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards, – checking the solenoid valve control. ► Multimeter checks: – wiring harness continuity, – solenoid valve resistance. ► Oscilloscope check: – command signal. ► Other checks: – pneumatic fitting condition, – conformity of the wastegate valve static setpoint, – turbocharging pressure dynamic check, – anti-pumping valve check, – choking, etc. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. 71 Fuel injection The "Injection phasing" function The "Injection phasing" function is used to actuate the injectors sequentially. This function uses the following components (figure 54): – the flywheel sensor, – the camshaft sensor, – the injectors. Figure 54. The "Injection phasing" function components. The camshaft sensor The camshaft sensor is a Hall effect sensor. The camshaft sensor target is inte- grated into the camshaft. The signal transmitted by the camshaft sensor to the computer is a square wave signal corresponding to the form of the target (figure 55). Figure 55. Sensor signal. 72  Fuel injection Operation programming The signals sent by the flywheel sensor and by the camshaft sensor are used to determine the Top Dead Centre and the start of inlet stroke of cylinder number 1. 1. The signal sent by the flywheel sensor is used to determine the Top Dead Centre of cylinder number 1. 2. The camshaft sensor signal is used to distinguish the start of the inlet stroke from the start of expansion. 3. The injectors are actuated at the right moment and in the correct sequence. Defect mode programming There is no defect mode for the flywheel sensor. The defect mode programs differ according to whether the engine has stopped or is running. FAULTY COMPONENT DEFECT MODE Flywheel sensor No defect mode When the engine is running, it continues to operate with sequential injection. Camshaft sensor With the engine stopped, various programs are possible. Injectors No defect mode Software phasing There is another sequential injection system that does not use a camshaft sensor. In this case the injection system uses software phasing. 1. The engine starts in semi-sequential mode. The injection computer increases the richness of an injector arbitrarily. 2. The computer checks if there has been an engine speed acceleration caused by the enrichment. 3. The computer deduces whether the cylinder concerned was on its inlet stroke and can go into sequential mode. 73 Fuel injection Camshaft sensor check ► Check with the CLIP fault finding tool: – conformity of values with the manufacturer’s standards. ► Multimeter checks: – wiring harness continuity, – supply. ► Oscilloscope check: – output signal display. NOTE The list of checks is shown as an example. Refer to the conformity values and the checking procedure in the technical reference material. 74  Fuel injection The "Injection cut" function The "Injection cut-out" function is used to achieve greater engine braking when decelerating. This function uses the following components (figure 56): – the "no load" signal from the throttle position sensor or the accelerator pedal position sensor, – the engine speed, – the "Vehicle speed" signal from the ABS computer, – the injectors. Figure 56. The "Injection cut-off" function components Injection cut-off programming When decelerating, if the engine speed and vehicle speed are above a certain value, the computer cuts the supply to the injectors. If the engine speed or vehicle speed falls below a threshold value, injection is restored to maintain an idling speed. The injection cut-out function is also used for over-revving protection. If the engine speed exceeds the maximum speed set value, the computer cuts the injectors. NOTE The maximum speed set value depends on the coolant temperature and a delay after the engine start. 75 Fuel injection Defect mode programming In the event of a "no load" signal or "Vehicle speed" signal fault, there is no injection cut. FAULTY COMPONENT DEFECT MODE "No load" signal Deactivated function Flywheel sensor No defect mode Vehicle speed signal Deactivated function Injectors No defect mode 76  Fuel injection The "Air conditioning" function The "Air conditioning" function enables air conditioning actuator operation under certain conditions. This function uses the following components (figure 57): – the air conditioning computer, – the flywheel sensor, – the full load signal sent by the throttle position sensor or the accelerator pedal position sensor, – the coolant temperature sensor, – the air conditioning compressor clutch, – the heating resistors. Figure 57. The "Air conditioning" function components Operation programming The injection computer enables air conditioning compressor engagement-on if all the requisite conditions are fulfilled. In the following operating phases, the injection computer may shut down the air conditioning compressor: 1. A high engine speed, 2. A power request. 3. An excessive engine temperature. 77 Fuel injection In the following operating phases, the injection computer deactivates the operation of the heating resistors in the air conditioning system: 1. After starting the engine during a timed period based on the engine tem- perature. 2. During large loads at low speed. Defect mode programming There is no defect mode. A "full load" signal or coolant temperature sensor fault will result in air conditioning compressor shutdown. FAULTY COMPONENT DEFECT MODE Air conditioning computer No defect mode "Full load" signal Deactivated function Coolant temperature sensor Deactivated function Air conditioning compressor clutch No defect mode Heating resistors No defect mode 78  Fuel injection The "Antipercolation/Coolant Temperature Management" function Percolation is the formation of bubbles in the fuel supply circuit due to excessive temperature. Percolation makes starting difficult. Coolant temperature management or GCTE controls cooling of the engine and the "Antipercolation" function and prevents faults when starting with a warm engine. These functions use the following components (figure 58): – the coolant temperature sensor, – the Cooling Fan Assembly relay. Figure 58. "Antipercolation/GCTE" function components. NOTE In the event of excessive temperature, the injection computer switches on the coolant temperature warning light on the instrument pan