Serial Data Power Mode

On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle the PMM is the BCM. The BCM uses 3 signals from the ignition switch. These are the Ignition 0 (Unlock), Ignition 1 (Run/Crank), and Accessory.

To determine the correct power mode the BCM uses:

The state of these signals
The sequence of switch closures received by the BCM
The status of the engine run flag

The chart indicates the power modes detected and transmitted by the BCM:

Correct Ignition Switch Inputs

Ignition Key Position	Power Mode Parameter	Engine Running	Sampled Ignition Signal State
Ignition Key Position	Power Mode Parameter	Engine Running	Ignition Accessory	Ignition 1 (Run/Crank)	Ignition 0 (Unlock)
OFF	Off-Awake or RAP	No	Inactive	Inactive	Inactive
UNLOCK	Unlock or RAP Unlock	No	Inactive	Inactive	Active
ACC	Accessory	No	Active	Inactive	Active
ON	Run	No	Active	Active	Active
START	Crank	No	Inactive	Active	Active
ON	Run	Yes	Active	Active	Active