Power Mode
Power Mode Description and Operation
Serial Data Power Mode Master
Power to many of this vehicles circuits is controlled by the module that is designated the power mode master. This vehicles power mode master is the body control module (BCM). The ignition switch is a low current switch with multiple discrete ignition switch signals to the power mode master for determination of the power mode that will be sent over the serial data circuits to the other modules that need this information. The power mode master will also activate relays and other direct outputs of the power mode master as needed. The power mode master determines which power mode (Off, Accessory, Run, Crank Request) is required, and reports this information to other modules via serial data. Modules which have switched voltage inputs may operate in a default mode if the power mode serial data message does not match what the individual module can see from its own connections.
The power mode master receives ignition switch signals to identify the operators desired power mode. The Power Mode Parameters table below illustrates the correct state of these input parameters (circuits) in correspondence to the ignition switch position:
Relay Controlled Power Mode
The BCM uses the discrete ignition switch inputs Off/Run/Crank Voltage, Accessory Voltage, and Ignition 1 Voltage, to distinguish the correct power mode. The BCM, after determining the desired power mode, will activate the appropriate relays for that power mode.
The retained accessory power relay remains on for a timed period after the Ignition key is removed. Refer to Retained Accessory Power Description and Operation Retained Accessory Power for more information on the retained accessory power function.
Push Button Start (If Equipped)
The ignition mode switch has 2 LEDs that indicate the vehicle power mode. When the vehicle is in the off mode, both LED's will be off. Pressing the ignition mode switch button once (without the brake pedal applied), the vehicle enters the accessory mode and the amber LED (ACC) will illuminate. The accessory mode has a 5 minute timeout to reduce battery drain. Pressing the ignition mode switch button a second time (without the brake pedal applied), the vehicle enters the run/start mode (without the engine running) and the green LED (Run/Start) will illuminate. Pressing and holding the push button start switch for at least 5 seconds will place the vehicle in run/start mode (without the vehicle running) and the green LED (Run/Start) will illuminate. With the ignition off (with the brake pedal applied), pressing the ignition mode switch button once, the vehicle will enter run/start mode and the green LED (run/start) will illuminate. This will start the engine. Both LED's have the voltage supplied from the body control module (BCM). The ignition mode switch sends the ignition mode switch status to the passive entry passive start module (PEPS) and to the BCM. The PEPS module sends a redundant signal to the BCM with the ignition mode switch status.
Battery Saver Mode (Transport Mode) (If Equipped)
The battery saver mode (transport mode) reduces the parasitic load of some modules during overseas shipment or during vehicle storage conditions. This improves the drain time on the battery (up to 70 days without the battery going dead). When the vehicle is in transport/storage, some features may have reduced functionality while in the battery saver mode (transport mode), such as disabling the Remote Function Actuator or content theft features.
The battery saver mode (transport mode) incorporates a latching relay that when enabled disconnects some modules from their ignition power or memory power sources. Battery saver mode (transport mode) is initiated by turning on the hazard flashers and then turning the ignition key into the crank position or pushing the push button start switch (if equipped) for greater than 15 seconds. After battery saver mode (transport mode) has been enabled, the BCM may not send the command to unlatch the relay until after the ignition has been switched to the off position for up to 1 minute. In battery saver mode (transport mode) the BCM will send a command to latch the relay for operation of those modules while the ignition is in the run position and then again unlatching the relay after the ignition is turned off. The mode is disengaged by repeating the previous process causing the relay to latch in the other direction. The DIC (if equipped) will display Transport Mode is On when the transport mode is enabled and Transport Mode is Off when the transport mode is disabled. For vehicles not equipped with a DIC, the battery indicator light will constantly flash on the Instrument Cluster when transport mode is enabled. Once the vehicle is running and the hazard flashers are on, turning the ignition key into the crank position or pushing the push button start switch (if equipped) for greater than 15 seconds will latch the relay in the other direction. This feature can be used as many times as necessary if the vehicle is to be stored for an extended period of time.
BCM Awake/Sleep States
The BCM is able to control or perform all of the BCM functions in the awake state. The BCM enters the sleep state when active control or normal monitoring of system functions has stopped and a time limit has passed. The BCM must detect certain wake-up inputs before entering the awake state. The BCM monitors for these inputs during the sleep state.
The BCM will enter the awake state if any of the following wake-up inputs are detected:
* Activity on the serial data line
* Detection of a battery reconnect
* Any door open signal
* Headlamps ON
* Key-in-ignition
* Ignition ON
* Park lamps ON
* Keyless entry or remote start message
The BCM will enter a sleep state when all of the following conditions exist:
* The ignition switch is OFF, key out.
* No activity exists on the serial data line.
* No outputs are commanded.
* No delay timers are actively counting.
* No wake-up inputs are present.
If all these conditions are met, the BCM will enter a low power or sleep condition.