Note. See also Section Troubleshooting.
The ignition and power systems are interrelated components of the engine management system, so some of its components may also perform functions related to the power system.
General information
Ignition and power systems have a common diagnostic system designed to store fault codes (DTC) and performing diagnostics. If a failure is detected, the control unit stores the corresponding DTC code in memory, which can be read using a special scanner.
Reading the information stored in the ECM's memory will, in most cases, determine the causes of engine failures. Analysis of read information using a list of codes (see Specifications) allows you to localize the source of failure at the level of a particular element, or its electrical wiring circuit.
Attention! A visual check of the wiring and connectors is not enough - be sure to read the information stored in the memory of the control unit!
Preliminary checks
If a malfunction occurred shortly after servicing a node, first of all, this node and its neighboring components should be carefully examined - it is possible that the cause of the failure is associated with an elementary violation of the quality of the contact connection.
When looking for the causes of a malfunction of the engine (for example, a drop in the developed power) it always makes sense to check the compression in the cylinders (see chapter Engine). Also make sure that the air and fuel filters are replaced in accordance with the maintenance schedule (see chapter Vehicle settings and routine maintenance).
Do not forget to clear the memory of the control unit after reading the fault codes and making the appropriate corrections.
1. Open the hood and check the reliability of fixing the wire ends on the battery terminals, make sure that there are no signs of oxidation of the terminal connections. If necessary, take appropriate troubleshooting measures, replace failed components. At least carefully study the condition of the ground buses and their terminal connections, - the contact surfaces of the corresponding ground elements (powertrain/body panels) must be absolutely clean and free from signs of corrosion.
2. Carefully inspect all visible electrical wiring inside the engine compartment, check the reliability of the contact connections. Replace the electrical wiring that has pronounced signs of damage, following the correct laying of the harnesses; if necessary, tighten the loose fasteners of the nodes against which the insulation has frayed.
Note. The risk area is always the wiring that runs close to components that have been serviced most recently.
3. It should be remembered that the conductive conductors of the electrical wiring may be damaged if there are no signs of damage to the insulation - in such a situation, an external examination will not give positive results. Such damage can occur as a result of wires being pulled out, or in violation of their laying routes.
4. It is possible to restore damaged electrical wiring by soldering in the area where the shunt wire is broken - soldering ensures the reliability of electrical contact. To repair the insulation, use insulating tape, or put a piece of heat shrink tubing on the wire. the best (though not the cheapest) The way to eliminate all failures associated with damage to the wiring is to replace the failed wire.
5. After completing the refurbishment / selecting a replacement, monitor the correct routing of the corresponding harnesses, paying special attention to sections of routes passing near heated surfaces and moving components in the engine compartment. Make sure that the harnesses are securely fastened in all provided intermediate clamps.
6. Check the condition of all available terminal connections, check the reliability of fastening of the wiring connectors. If traces of corrosion are detected on the inner surface of the connector (white or green deposits, rust deposits), or if it is excessively dirty, remove the connector from the corresponding terminal and clean thoroughly, if necessary using a special spray. Severely damaged connectors must be replaced, in some cases complete with wiring harness.
7. After cleaning the connector from corrosion, pack it with preservative grease before reinstalling.
8. The vehicles covered in this manual use a crankshaft position sensor (CKP), which determines the TDC position of the piston of the first cylinder. Excessive dirt or dust on the sensor can cause misfiring.
9. Carefully inspect the hoses and tubes of all vacuum lines in the engine compartment. Check the tightness of the mounting clamps, make sure that there are no deformations, cracks, cuts, delaminations or other physical damage to the hoses and tubes. Carefully examine the fitting assemblies for signs of leakage (see chapter Vehicle settings and routine maintenance).
10. Evaluate the condition and check the patency of the PCV system hoses. Excessive pollution or violation of the patency of the hoses entails a violation of the stability of the engine speed, especially at idle.
11. Moving from the fuel tank to the fuel rail (through the fuel filter) along the fuel lines, carefully examine the condition of the fuel lines. Pay special attention to the joints of the pipes, where cracks are most often formed, through which leaks begin to develop. Replace damaged sections of fuel lines.
12. Check the condition of the air cleaner filter element. An excessively dirty filter can significantly increase the total aerodynamic resistance of the intake air tract, which directly affects the power developed by the engine. Replace the filter element if necessary.
13. Start the engine and leave it running at idle.
Attention! When performing any work in the engine compartment with the engine running, be extremely careful - try not to touch the heated surfaces of the power unit and the exhaust system, do not allow hair and clothing to get into moving components (cooling fan, accessory drive belt)!
14. Moving from the air intake to the air cleaner and further to the throttle body, make sure that there are no signs of the development of air leaks in the intake tract. You can use soapy water to find sources of leaks. Make the necessary corrections.
15. Drive the car on a lift and examine the condition of the components of the exhaust system. Make sure that there are no signs of the development of leaks - the easiest way to identify leaks in the exhaust tract is by clogging its outlet, - a characteristic whistle and smoke will help to localize the damaged area. Tighten loose clamps/replace failed gaskets, replace damaged sections.
16. At the final stage of the check, with the engine running, pull the contact connectors of its electrical wiring one by one - a change in the nature of the engine operation will indicate poor contact quality, - make the necessary corrections, replace the failed sections of the electrical wiring.
17. If during the preliminary checks it is not possible to identify the cause of the violation of the stability of the engine, the car should be driven to a service station to perform a more thorough diagnosis using special equipment.