7.2.2. Diagnostics of malfunctions - the general information and preliminary checks

See the Section Diagnostics of Malfunctions.

General information

The system of ignition of the petrol engine is integrated with system of injection of fuel and is run by the uniform block of electronic control of ECM (see the Head of the Power supply system, release and decrease in toxicity of the fulfilled gases).

The system of ignition and fuel system have the general diagnostic system intended for identification of violations, preservation of codes of malfunctions and search of causes of failures. At malfunction emergence the module of management writes down in the processor memory.

The reason of failures in operation of the engine, most often it is possible to localize by data read-out, ECM which are stored in memory of the block of self-diagnostics. After the refusal is identified, it is possible to pass to performance of checks of a state and serviceability of functioning of the corresponding knots and components. Remember that visual check of a condition of an electrical wiring and its contact sockets is not enough, - surely consider information which is stored in memory of the module of management.

Preliminary checks

If malfunction arose soon after service of any knot, first of all, carefully check the corresponding element. Perhaps, the reason is covered in negligence of installation of a component or connection to it the contact socket of an electrical wiring.

At investigation of the reasons of falling of the power developed by the engine in addition to the listed below checks check also compression pressure in cylinders (see the Head Dvigateli). The probability is not excluded that with the reason of decrease in efficiency of return of the power unit it is covered in the negligent relation to implementation of such procedures of regular service of the car as replacement of the fuel filter or filtering air cleaner element (see Chapters of Control and routine maintenance of the car, Dvigateli and the Power supply system, release and decrease in toxicity of the fulfilled gases).

Remember that after reading of codes of malfunctions memory of the module has to be cleared. Cleaning of memory is made by means of the same device which is used when reading codes (see the Section System of Onboard Self-diagnostics of OBD - the general information).


  1. Open a cowl and check reliability of fixing of tips of wires on polar plugs of the rechargeable battery. Make sure of lack of signs of oxidation of plugs, in case of need make their cleaning (see the Head Nastroyki and routine maintenance of the car). Check reliability of fixing of terminal connections of tires of grounding and quality of electric contact in them, - the interfaced surface have to be absolutely pure and free from oxidation products.
  2. Attentively examine all visible conducting laid in a motive compartment, check reliability of all electric connections, - pay attention to strong indications of damage. In case of identification of cracks, cuts, attritions of isolation you make replacement of defective units. The break of a wire can result from a nebrezhnoyustanovka of any knot, - the wire can melt at contact with elements of system of release. Violation of correctness of its laying in a motive compartment after performing procedures of repair or service of any knot is the most probable cause of damage of conducting.
  3. Conducting can be damaged or short-circuited even in lack of obvious damages of isolation, at the same time external survey will not yield results. Damages of this sort can arise after a pulling of wires or the wrong placement of plaits in a motive compartment.
  4. The damaged conducting can be restored by a vpaivaniye in a rupture of a piece of the new conductor, - the soldering is the necessary condition giving a guarantee obtaining reliability of contact. Repairs of the damaged isolation are usually made by means of enough an insulating tape, or a piece of a thermoshrinkable tube. If damages are considerable, or the damaged wire plays an essential role, the most correct (though) the decision replacement of the corresponding plait will be rather expensive.
  5. After restoration of the damaged electrical wiring track correctness of laying it in a motive compartment, - plaits should not concern the warmed surfaces of the power unit. Do not forget to fix wires in all provided intermediate clamps.
  6. Check a state and reliability of fixing of all available contact sockets. All clamps have to be established. At identification on the internal surface of the socket of products of oxidation (white or green deposits, and also metal corrosion traces) or signs of excessive pollution, disconnect it from the corresponding plug and carefully smooth out, it is desirable with application any of special cleaners, - ask in shops of automobile accessories. Seriously damaged sockets are subject to replacement, - sometimes in a set with a plait of the electrical wiring brought to it.
  7. Having removed all traces of oxidation and dirt, fill the socket with the preserving lubricant (consult in a workshop of car service) and establish on the place, - track reliability of fixing of the socket.
  8. The inductive sensor of position of the CKP crankshaft delivering to ECM information on the frequency of rotation of the engine and the provision of VMT of the piston of the first cylinder is included in a basic equipment of all models. Pollution of a sensitive head of the sensor oil or dust can lead to emergence of admissions of ignition. The description of procedures of removal and installation of the CKP sensor see in the Head of the Power supply system, release and decrease in toxicity of the fulfilled gases.
  9. Attentively study a condition of all vacuum lines laid in a motive compartment. Check reliability of tightening of fixing collars, make sure of lack of cracks, stratifications and other damages of hoses. Examine hoses on existence of signs of violation of passability (twisting, squeezing, bending, etc.). Pay special attention to the hoses laid near keen edges, and also a state tense on unions to sites. The damaged hoses are subject to replacement.
  10. Check a condition of hoses of system of ventilation of a case (PCV). Make sure of lack of signs of violation of passability. The quantity of hoses and the place of their installation of system can vary depending on car model, however at any execution of model there is a hose connecting the top part of the engine to a sleeve of an air inlet or the inlet pipeline. PCV hoses usually connect to the inlet pipeline also the block of cylinders (or a maslozalivny mouth) and serve for transportation of crankcase gases and oil evaporations in combustion chambers. Blocking of passability of these hoses usually brings to violation of stability of functioning of the engine, especially on single turns.
  11. Moving along fuel-supply lines from the fuel tank to the fuel highway, attentively study a condition of lines of a path of a power supply system and their nipple sockets. At identification of signs of damage or deformations replace defective section. Special attention should be paid to a condition of places of a joint of lines where the cracks leading to development of leak of fuel are most often formed.
  12. Check correctness of laying and adjustment of a cable of gas (see the Head of the Power supply system, release and decrease in toxicity of the fulfilled gases). The cable should not be bent strongly. In the presence of suspicions on violation of serviceability of functioning of hummock assembly make its replacement.
  13. Uncover the case of the air cleaner and check a condition of the filtering element (see the Head Nastroyki and routine maintenance of the car), in case of need blow, or replace the polluted filter as increase in resistance of its passability can lead to noticeable decrease in the power developed by the engine.
  14. Start the engine and leave it working at single turns.

When performing any works in a motive compartment at the working engine observe extreme care. Try not to touch the warmed surfaces of the power unit and such moving components as driving belts and a krylchatka of the fan. Try to follow strictly all necessary precautionary measures and safety regulations.

  1. Moving from an air inlet to the air cleaner and further to the throttle case, be convinced of lack of signs of development of leaks in the inlet air highway (including vacuum hoses). Leaks can be revealed on characteristic whistle, - for greater reliability moisten the suspected site with solution of soap water. If the hose is damaged, kind of work of the engine will change, and on the processed surface of a hose there will be bubbles (or, depending on pressure in a hose, water can begin to be soaked up inside). At detection of leak tighten the corresponding collar, or replace the damaged hose.
  2. Tire out the car on a platform / a viewing hole (or and establish to its poddomkratta on props) and attentively study a condition of components of system of production of the fulfilled gases from a final collector to a cut of back section. Sources of leak of the fulfilled gases most simply come to light on emergence of characteristic whistle at a system outlet blockage, - tighten the corresponding fixture, or replace the burned-through section.
  3. Further check consists in serial movement of each socket on the corresponding plug at the working engine. Unreliability of electric contact will be shown on change of kind of work of the engine. Make necessary corrections, replace the failed components, - some sockets change complete with the electrical wiring plaits brought to them.
  4. If during the listed preliminary checks it is not possible to establish the reason of the violation taking place, the car should be driven away on car repair shop for the purpose of performing full diagnostics of a control system with use of the special equipment.