Modes of Operation
The PCM has 2 modes of operation:
- Bypass mode
- Ignition Control (IC) mode
Bypass mode is used by the ICM to control the triggering of each coil for base spark timing. During bypass mode the timing is fixed at 10° BTDC and the PCM does not apply 5 volts to the IC timing signal circuit. The Bypass mode is used during each of the following conditions:
- Crank
- Engine running below a desired RPM
IC Mode is used by the PCM to accurately control spark timing for all driving conditions. During IC mode the PCM is receiving the 18X and the 3X reference pulses from the ICM and is supplying 5 volts to the IC timing signal circuit. This allows the PCM to control spark timing. Knock Sensor (KS)