DIRECT IGNITION SYSTEM (DIS)
Ignition and spark distribution are controlled by DIS. DIS uses 4 double-ended ignition coils located at the rear of the engine. ECM provides internal switching of ground circuit for each coil, which operate on a waste spark principle. A spark is delivered simultaneously to 2 cylinders, one on its compression stroke and the other on its exhaust stroke. Coil No. 1 feeds cylinders No. 1 and 6. Coil No. 2 feeds cylinders No. 5 and 8. Coil No. 3 feeds cylinders No. 4 and 7. Coil No. 4 feeds cylinders No. 2 and 3. Failure of any coil will cause a misfire in 2 cylinders.
Ignition timing is controlled primarily as a function of engine speed and load. Engine load is sensed by Mass Airflow (MAF) sensor. Engine speed is sensed by a Crankshaft Position (CKP) sensor. ECM determines correct firing sequence and timing of ignition coils from input provided by Camshaft Position (CMP) sensor. An ignition coil fault is indicated by illumination of the MIL.
Ignition Relay
The ignition relay supplies power feed to ignition coils (6.5 amps), purge control valve (1.0 amp) and HO2S heaters (8.0 amps, non-continuous). Relay is ignition switch controlled. When ignition switch is turned off, power supply to ignition coils is immediately cut. Failure of this relay will result in no ignition.
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Tuesday, January 5th, 2010 AT 3:51 AM
