System Operation

Conventional Ignition Switch - without Intelligent Access (IA)

System Operation

System Diagram





Network Message Chart

Module Network Input Messages - BCM (Body Control Module)






OFF

When the ignition switch is turned to the OFF position, the BCM (Body Control Module) sends an "ignition off" status in the ignition mode message to the other modules over the MS-CAN (Medium Speed Controller Area Network).

ACC

When the BCM (Body Control Module) receives the ACC voltage input from the ignition switch, the BCM (Body Control Module) sends out the ignition mode message on the MS-CAN (Medium Speed Controller Area Network) and allows operation of continuously powered modules, such as the radio.

ON

When the BCM (Body Control Module) receives the ON voltage input from the ignition switch, it activates the ignition and accessory relays, providing ignition power to the various vehicle systems and modules. The BCM (Body Control Module) also sends out the ignition mode message on the MS-CAN (Medium Speed Controller Area Network).

START

When the BCM (Body Control Module) receives the ON voltage input from the ignition switch (also present in the START position), it activates the ignition relay, providing ignition power to the various vehicle systems and modules. The PCM (Powertrain Control Module) send an engine status message to the BCM (Body Control Module) over the HS-CAN (High Speed Controller Area Network) and while the engine is cranking, the BCM (Body Control Module) inhibits the accessory relay. The BCM (Body Control Module) also sends out the ignition mode message on the MS-CAN (Medium Speed Controller Area Network).

The ignition switch START circuit is hardwired to the PCM (Powertrain Control Module). The PCM (Powertrain Control Module) uses the ignition switch START input to determine when to activate the starter motor relay. REFER to Starting System .