Note. See also Section Troubleshooting.
General information
Components of ignition/engine control systems are among the elements of increased reliability and most failures, as a rule, turn out to be associated with a violation of the quality of contact connections or damage to electrical wiring. Breakdowns of explosive electrical wiring most often occur as a result of contamination, moisture or damage to the insulation. Before concluding that a system component has failed, always first check the condition of the associated electrical wiring and its contact connections.
Do not check the correctness of the voltage supply to the spark plugs by disconnecting the electrical wiring from them and testing it on the engine ground - this kind of diagnosis is not only associated with the risk of electric shock, but also with the risk of failure of the ECM or ignition coil. In case of violation of the stability of the engine's operating speed, it is also not necessary to identify a faulty cylinder by sequentially disconnecting the electrical wiring from the spark plugs.
The checks listed below allow you to determine the cause of malfunctions, the symptoms of which are quite obvious (starter failure, misfiring, etc.). Some, less obvious, violations may not show themselves due to the automatic transition of the control system to the emergency mode of operation and manifest themselves only in an increase in fuel consumption, a violation of the stability of the idle speed, a reduction in the efficiency of the engine's output, the occurrence of detonations, etc. - contact for advice car service specialists.
Engine won't start
Note. Remember that if the anti-theft device fails, it is not possible to start the engine - turn off the immobilizer (refer to the owner's manual of the vehicle - ask in automotive literature stores).
If the starter does not crank the engine, or rotates it too slowly, first of all check the proper functioning of the starter itself, as well as the condition of the battery. Connect a voltmeter to the battery terminals and measure its output voltage while cranking the engine with the starter. If the measurement result is less than 9.5 V, the condition of the battery, starter and charging system components should be checked.
Attention! Do not activate the starter continuously for more than 10 seconds!
If the engine does not start despite the correct rotation of the starter, check the condition of all the components of the ignition circuit BB.
Acting strictly in accordance with the manufacturer's instructions, connect the strobe and turn the engine over with the starter - the activation of the strobe lamp confirms that the HV voltage supply to the spark plugs is correct. Check the condition of the spark plugs themselves. If the stroboscope does not work, evaluate the condition of the BB electrical wiring (if equipped, see Chapter Ongoing care and maintenance). If sparking is good, proceed in accordance with the recommendations given in Section Checking and adjusting the ignition timing.
If there is no sparking, make sure the coil is in good condition (ek) ignition (the easiest way is to replace the coil with a known good one - alternatively measure the resistance of the windings). Do not rush to throw away the coil suspected of failure - first make sure of the quality and reliability of its contact connections.
Another reason for failure to start the engine may be a violation in the powerful buffer output stage, which is an integral part of the engine control module (ECM), as well as a malfunction of any of the information sensors of the control system, or another related unit, check the ECM memory for the presence of diagnostic codes recorded in it (DTC).
Note. DTCs are read using special diagnostic equipment (see part Diagnostics of electronic control systems and diagnostic equipment).
Misfire
The cause of misfiring is most often a violation of the quality of the contact connections of the electrical wiring at the terminals of the ignition coils or any of the information sensors.
Switch off the ignition and check the corresponding connectors for signs of oxidation and for secure fit at the terminals.
If equipped, check the condition of the BB wiring. Make sure that the wires are securely fastened in all provided intermediate clamps, make sure that the wires do not come into contact with the metal parts of the engine - if a wire with broken insulation touches the metal, then sparking will occur not between the contacts of the corresponding spark plug, but at the breakdown site when the engine is running. If even a slight damage to the insulation of at least one wire is detected, replace the entire set.
Note. The easiest way to verify the condition of the explosive wiring is by replacing the entire set with a known good one.
To avoid the risk of incorrect connection, replace the spark plug wires one by one.
If the wiring is in good condition, the cause of misfiring may be the failure of the spark plug itself, or the coil assembly - replace the spark plugs (see chapter Ongoing care and maintenance), check the condition of the coil. A damaged or dirty crankshaft position sensor can also cause misfiring (CKP).
If the above checks fail to determine the cause of the problem, read the DTCs from the OBD memory (ECM).