Conventional Ignition Switch

OFF 

When the ignition switch is turned to the OFF position, the BCM receives no input from the ignition switch. The BCM interprets this as the ignition off state and communicates the ignition mode to the other modules by sending an ignition status message over the CAN.

ACC 

When the ignition switch is in the ACC position, the switch routes voltage through the ACC-designated circuit to the BCM. The BCM interprets this as the ignition accessory state and communicates the ignition mode to the other modules by sending an ignition status message over the CAN.

ON 

When the ignition switch is in the RUN position, the switch routes voltage through the ACC-designated and RUN-designated circuits to the BCM. The BCM interprets this as the ignition on state and the BCM activates the internal run/start relay, the BJB run/start relay (providing ignition power to the various vehicle systems and modules) and communicates the ignition mode to the other modules by sending an ignition status message over the CAN.

START 

When the ignition switch is placed in the start position, the switch routes voltage through the RUN-designated and START-designated circuits to the BCM. The BCM interprets this as the ignition start state and communicates the ignition mode to the other modules by sending an ignition status message over the CAN

Additionally, the ignition switch routes votlage to the PCM indicating a request to start the vehicle.

Ignition Key Inhibit 

The ignition key cylinder inhibit feature prevents the ignition lock cylinder from being rotated to the OFF position when the vehicle is not in PARK.

The key removal inhibit solenoid (part of the ignition switch) receives battery voltage at all times from the BCM fuse 18 (5A). The ground circuit for the key removal inhibit solenoid is routed through a park detect switch within the selector lever assembly and then to the BCM.

When the selector lever is in PARK, the park detect switch inside the selector lever assembly is open, preventing the solenoid from actuating. When the selector lever is moved out of PARK, the switch closes and completes the circuit to the BCM. The BCM controls the ground by means of a Field Effect Transistor (FET). The BCM enables the path to ground when it detects the vehicle is not in PARK based on messages received over the CAN.

When the selector lever is in PARK, the key removal inhibit solenoid deactivates and allows the ignition lock cylinder to be turned to the OFF position and the key to be removed.