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 BCM has multiple B+ circuits that feed into it. Each of those circuits are partitioned within the controller to drive certain outputs of the vehicle’s body functions. An open or short in any one of the B+ circuits may induce multiple codes/or a section of non-functionality within the BCM with the rest of the BCM functioning normally. In this case it is useful to refer to the power distribution schematics to determine if the non-functional partition of the controller shares a common B+ circuit. The ignition mode switch is a low current switch with a discrete ignition signal 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/Start) 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 mode switch signals to identify the operators desired power mode. The Power Mode Parameter table below illustrates the correct state of these input parameters in correspondence to the ignition mode switch with the transmitter to vehicle range:

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 for more information on the retained accessory power function.

The BCM uses discrete push button switch inputs, transmitter in range status, current power mode state, and brake pedal position state to distinguish the correct power mode (Off, Accessory Mode, Vehicle in Run/Start 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 for more information on the retained accessory power function.

The S38 Ignition Mode Switch has two LEDs that indicate the vehicle power mode. When the vehicle is in the Off ignition mode, both LEDs will be off.

With the vehicle in the OFF ignition mode, momentarily pressing and releasing the S38 Ignition Mode Switch with the brake pedal not pressed the vehicle will enter into the Accessory ignition mode and the amber LED will illuminate. The Accessory mode has a predetermined time-out to prevent battery drain. For details, refer “Ignition Positions” in the vehicle owner manual.

With the vehicle in the OFF ignition mode, pressing and holding the S38 Ignition Mode Switch for greater than 10 s with the brake pedal not pressed the vehicle will enter into Service Mode ignition mode and the green LED will illuminate. In this mode, the vehicle will be in the Run ignition mode without the engine running. Service Mode is used for vehicle service and diagnostics that does not required the engine to be running. Service Mode will remain on until the vehicle is manually turned OFF by pressing and releasing the S38 Ignition Mode Switch. There is not battery run-down protection and leaving the vehicle in Service Mode may result is a depleted battery.

With the vehicle in the OFF ignition mode, momentarily pressing and releasing the S38 Ignition Mode Switch with the brake pedal pressed the vehicle will start and the green LED will illuminate. Upon engine starting, the vehicle will remain in the Run ignition mode. If the vehicle is left in PARK with the engine running, the vehicle will automatically turn off after a predetermined amount of time. This time will vary depending if the keyless entry transmitter was left in the vehicle. For details, refer “Extended Parking” in the vehicle owner manual.

With the vehicle in any ignition mode except Off, momentarily pressing and releasing the S38 Ignition Mode Switch the vehicle will enter the Off ignition mode.

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.

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 a vehicle is in transport/storage, some features may be disabled or have reduced functionality while in the battery saver mode, such as disabling the Remote Function Actuator or content theft features. Transport mode is initiated by turning on the hazard flashers, applying the brake pedal, and then turning and holding the ignition key (if equipped) to the start position or pushing and holding the ignition mode switch with the brake pedal applied for greater than 15 s. The mode is disengaged by repeating the previous process. The DIC (if equipped) will momentarily display Transport Mode is On when it is enabled and Transport Mode is Off when it is disabled. For vehicles not equipped with a DIC, the battery indicator light will constantly flash on the Instrument Cluster when enabled. This feature can be used as many times as necessary if the vehicle is to be stored for an extended period of time.

Transport mode utilizes a latching relay that when enabled it disconnects some modules from their ignition power or memory power sources. When the mode is enabled and the vehicle is switched OFF, the BCM sends a momentary command to unlatch the relay disconnecting power up to 1 min after RAP is inactive. Every time the vehicle is switched ON the BCM will send a momentary command to latch the relay. This allows the use of all features when the ignition is ON. The BCM will send another command to unlatch the relay once the vehicle is switched OFF and RAP is inactive.

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.
• Ignition OFF, transmitter is out of range
• 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.