Electronic Ignition System: Metro

Ignition system circuit consists of a PCM, 2 ignition coil assemblies, Crankshaft Position (CKP) sensor, Camshaft Position (CMP) sensor, spark plugs and spark plug wires.

The PCM uses reference pulses from CKP sensor in order to determine engine speed for ignition and fuel injector operation. The PCM controls ignition timing by controlling the ignition coils.

Each ignition coil has a built-in ignition module (ignitor) that controls current flow in primary coil winding. When PCM signals ignition module to interrupt current flow, the electrical field around primary coil collapses and induces high voltage in secondary coil. Secondary coil voltage is delivered to spark plugs through each coil output terminal simultaneously (coil No. 1 - cylinders No. 1 and 4 or coil No. 2 - cylinders No. 2 and 3). The following are the most important inputs for determining ignition timing requirements:

• Engine speed
• Throttle Position (TP)
• Manifold Pressure (MAP)
• Engine Coolant Temperature (ECT)