Description
Ignition timing is controlled by the electronic control ignition timing system. The standard reference ignition timing data for the engine operating conditions are preprogrammed in the memory of the ECM (Engine Control Module).
The engine operating conditions (speed, load, warm-up condition, etc.) are detected by the various sensors. Based on these sensor signals and the ignition timing data, signals to interrupt the primary current are sent to the ECM. The ignition coil is activated and timing is controlled.
On-Vehicle Inspection
Inspect ignition coil assembly and Perform spark test
Scheme 17
Scheme 18
- Check for DTCs. NOTE: If a DTC is present, perform troubleshooting in accordance with the procedure for that DTC. (Refer to the DTC INDEX article)
- Check if sparks occur. Remove the engine cover. Remove the ignition coils. Using a spark plug wrench, remove the spark plugs. Disconnect the injector extension connectors. Ground the spark plug to the engine. Check if sparks occur at each spark plug while engine is being cranked. NOTE: Do not crank the engine for more then 5 seconds.
- If sparks do not occur, perform the following test.
- Using a spark plug wrench, install spark plugs.
- Install the ignition coils.
Description and Operation
An ignition coil is an induction coil in an engine's ignition system which transforms the battery's low voltage to the high voltage needed to create an electric spark in the spark plugs to ignite the fuel. Coils have an internal resistor while others rely on a resistor wire or an external resistor to limit the current flowing into the coil from the battery 12 V supply.
A spark plug is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture therein by means of an electric spark, while containing combustion pressure within the engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator.
