Electronic Ignition System: Prizm

The ignition system is of the Direct Ignition System (DIS) type and is controlled by PCM. The ignition system is composed of the following components:

• PCM
• Four Ignition Coil Assemblies
• Camshaft Position (CMP) Sensor
• Crankshaft Position (CKP) Sensor
• Spark Plugs

The PCM uses reference pulses from CKP sensor in order to determine engine speed. The PCM cannot operate ignition system or fuel injectors without the engine speed signal from CKP. The PCM controls ignition timing by controlling ignition coils. Each ignition coil has a built-in ignition module that controls current flow in primary coil winding. When current flow is interrupted, the electrical field around primary coil collapses and a high voltage is induced in the secondary coil. The secondary coil voltage travels from coil output terminal, through spark plug boot, and across spark plug gap to engine block. As a fail safe function, ignition control module sends an ignition confirmation signal back to PCM whenever primary field collapses.

The CMP sensor input is used to detect an engine misfire. The PCM also uses CMP sensor signal as an input for modifying fuel injection timing and ignition timing. The PCM receives information on engine status from various engine sensors and then selects the most appropriate ignition timing settings from within the PCM's programming. The following are the most important inputs for determining ignition timing requirements:

• Engine Speed
• Throttle Position
• Intake Air Volume
• Engine Coolant Temperature
• Knock Sensor Input

The ignition system components cannot be disassembled or repaired. A component that is diagnosed as faulty must be replaced as a complete unit.