Ignition System - 6-CYL & V8: Operation
The ECU and ignition coil are turned on whenever the ignition switch is in the "START" or "ON" position. When the engine begins turning the distributor shaft, the trigger wheel rotates with it.
Fig 1: Jeep Solid State Ignition (SSI) System Wiring Diagram, 6 Cyl. Engine. Note connections to MCU.
As each tooth passes the sensor, it interrupts the magnetic field around the sensor. This continual build-up and collapse of the field provides a signal to the ECU.
The ECU receives this signal and turns the power to the ignition coil's primary circuit off and on as each tooth passes the sensor.
The collapse of the magnetic field in the ignition coil primary circuit induces a high voltage surge in secondary. This current flows from the coil to the distributor, rotor, cap and spark plug wires.