Functional Description - Body Control Module (BCM)

The Body Control Module (BCM) is the gateway for all bus communications needing to be gated from one bus network to a different bus network.

The BCM obtains battery voltage information from the Intelligent Battery Sensor (IBS) over the Local Interface Network (LIN) bus. The BCM is the LIN master for the IBS and manages the IBS initialization, LIN communication, signal gating and IBS diagnostics.

Load Shedding 

Using the LIN, the BCM communicates with the IBS to provide load shedding. Load shedding is activated under the following conditions:

• The engine must be running with an engine speed equal to or higher than 400 RPM for greater than 50 seconds.
• The battery State of Charge (SOC) supplied signal value sent by the IBS over the LIN bus to the BCM must be less than or equal to 55%.
• The battery voltage measured by the IBS and supplied to the BCM over the LIN bus must be less than or equal to 12.2 volts.

When the vehicle is in a load shed operating state, the BCM will bus a signal to the Instrument Panel Cluster (IPC) to illuminate the "Battery Saver On" indicator.

If the battery SOC rises to a level equal to or greater than 65% and the battery voltage rises to 13 volts or higher, load shedding will begin to reverse itself putting the vehicle back to a normal operating state.

Any transition of the ignition state will reset all of the load shed output signals and therefore cancel load shedding operation.

Battery Critical State 

If the battery SOC is equal to or less than 35% and the battery voltage is equal to or less than 11.8 volts, a "Battery Reached Critical State" output signal is broadcast by the BCM. Another condition to set this output signal is that the battery voltage is less than or equal to 10.9 volts and the state of charge is less than or equal to 55%.

When the battery reaches critical state, only electrical loads essential to vehicle operation are allowed to be turned on. The following actions are recommended to be taken:

• Heated seats and the heated steering wheel are disabled for the duration of the ignition cycle
• Rear defroster and heated mirrors time out in 30 seconds each time the customer turns them on for the duration of the ignition cycle
• The Heating, Ventilation, and Air Conditioning (HVAC) system is allowed only minimal loads for visibility requirements for the duration of the ignition cycle
• On vehicles equipped with an eTorque system, the Power Inverter Module (PIM) is disabled for the duration of the ignition cycle
• Audio and Telematic systems will only allow minimal loads for communications and emergency requirements for the duration of the ignition cycle

There is no load shed recovery for a battery critical state and the vehicle operation will remain in this state until the ignition is cycled.

Inputs

• Battery voltage, temperature and state of charge information is provided through LIN communication from the IBS

Outputs

• IBS LIN communication for strategy management
• The BCM broadcasts the battery information on both the Controller Area Network-Chassis (CAN-C) and the CAN-Interior High Speed (CAN-IHS) data bus networks
• Load shedding management to the relevant nodes on all bus networks