START - Conventional Ignition Switch
When the BCM receives the ON voltage input from the ignition switch (also present in the START position), it activates the ignition relay, providing ignition power to various vehicle systems and modules. The PCM communicates the state of the engine by sending an "engine state" and "power pack status" message over the HS-CAN to the BCM. While the engine is cranking, the BCM inhibits the accessory relay. The BCM communicates the state of the ignition to the other modules by sending an "ignition status" message over the MS-CAN.
The ignition switch START circuit is hardwired to the PCM. The PCM uses the ignition switch START input to determine when to activate the starter motor relay. For information on the starting system: