Ignition Control

IGNITION CONTROL
During primary current-flow time (coil saturation) the coil is connected to ground through the power output transistor (power stage) via the Engine Control Module.

Based on load conditions received by the Engine Control Module in relation to various engine speeds a three dimensional ignition performance characteristic "Basic Ignition Map" is used to optimize ignition for the most favorable exhaust gas and fuel consumption performance for any given load or speed condition.

When the throttle valve is in the closed position, the bottom line of the basic ignition map is selected as the idle/coast characteristic.

For engine speeds below the nominal values, the ignition timing is advanced to obtain idle stabilization.

For coasting, ignition timing is programmed to obtain minimum exhaust gas pollutants and optimum driveability performance.

For the wide open throttle operation, the top line of the basic ignition map is selected. This full-load characteristic is programmed with engine knock limits taken into consideration.

For very high ambient temperatures the ignition is retarded as a function of engine and intake air temperature.

ON-BOARD DIAGNOSTICS
In the event of a system malfunction, circuit information is stored in the internal memory of the Engine Control Module.

The Engine Control Module will give priority to those items which can cause the vehicle to exceed exhaust emission standards. In addition to being stored in memory, an emissions-related failure will cause the "Check Engine" light to illuminate on the instrument cluster.