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:
Power Mode Parameters
Ignition Switch Position
|
Power Mode Transmitted
|
Ign. Off / Run / Crank (Off / Run Crank Voltage Circuit)
|
Ignition Accessory / Run (Accessory Voltage Circuit)
|
Ignition Run / Crank (Ignition 1 Voltage Circuit)
|
Off Key Out
|
Off
|
Key Out/ACC
|
Inactive
|
Inactive
|
Off Key IN
|
Off
|
Key In/Off
|
Inactive
|
Inactive
|
Accessory
|
Accessory
|
Key Out/ACC
|
Active
|
Inactive
|
Run
|
Run
|
Run
|
Active
|
Active
|
Start
|
Crank Request
|
Crank
|
Inactive
|
Active
|
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 for more
information on the retained accessory power function.
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. |
• |
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.
|