Ignition Control PCM Output

Ignition Control PCM Output

The PCM provides a zero volt (actually about 100 mV to 200 mV) or a 5-volt output signal to the ignition control (IC) module. When the ignition control (IC) module receives the 5-volt signal from the PCM, it provides a ground path for the B+ supply to the primary side of the coil and creates a magnetic field in the coil. When the PCM shuts off the 5-volt signal to the ignition control module, the ground path for the primary coil is broken. The magnetic field collapses and induces a high voltage secondary impulse which fires the spark plug and ignites the air/fuel mixture.

The ignition control (IC) spark timing is the PCM's method of controlling the spark advance and the ignition dwell.

The IC spark advance and the ignition dwell are calculated by the PCM using the following inputs:
- Engine speed.
- Crankshaft position (58X reference).
- Camshaft position (CMP) sensor.
- Engine coolant temperature (ECT) sensor.
- Throttle position (TP) sensor.
- Vehicle speed (vehicle speed sensor).
- PCM and ignition system supply voltage.