See Figures 1, 2 and 3
The 5.7L (VIN P and 5) engines utilize the Opti-Spark distributor ignition system, which consists of a distributor assembly, control circuitry and an external coil. In the Opti-Spark system, all ignition timing is controlled by the Engine Control Module (ECM) or Powertrain Control Module (PCM), based on signals from the distributor's internally mounted optical camshaft position sensor. There is no way to bypass the ECM/PCM control or to adjust/set ignition timing on this system.
In later years, this system is referred a simply the Distributor Ignition (DI) system.
The distributor assembly is mounted directly to the front end of the camshaft, next to the water pump. It directs the spark from the ignition coil to the appropriate spark plug secondary wire, through the rotor. The secondary output connectors in the distributor cap are each connected to an individual spark plug. The connectors in the cap are arranged for convenience in routing the spark plug wire harness assemblies. The corresponding cylinder number is molded into the distributor cap next to each output connector.
The distributor also contains a signal disk and 2 optical Camshaft Position (CMP) sensor assemblies. These components send signals to the ECM/PCM for spark timing control.
The ignition coil/ignition control module assembly provides spark to the distributor assembly, timed by signals from the ECM/PCM. The ECM/PCM combines the camshaft position information supplied by the distributor with other system parameters and calculates the required spark advance and coil dwell. The ECM/PCM signals the ignition control module, which turns on, then off, the primary current to the ignition coil. When the primary current flow stops, high voltage induced in the ignition coil secondary winding becomes the spark voltage for the spark plug. The spark voltage is delivered to the distributor assembly through the coil secondary wire, and is then directed to the proper spark plug connector by the distributor rotor.