Body Control Module (BCM)

The BCM has two functions:

• it is the gateway for the battery status signals coming from the Intelligent Battery Sensor (IBS) to the Controller Area Network-Chassis (CAN-C) network
• it receives information from some vehicle loads and manages voltage limits by increasing or decreasing the generator voltage output. The battery voltage limits are monitored while these requested voltage changes are occurring. The BCM calculates the limits of the maximum charging voltage by utilizing a LIN bus message from the IBS indicating the battery temperature.

Depending on the state of some electrical loads and the maximum charging limit already calculated by the BCM, the BCM will set the minimum and maximum voltage limits for the generators target voltage. These limits are then broadcast on the CAN-C network.

The following signals are transmitted by BCM to the PCM using the CAN-C network:

• The battery current
• The battery temperature (°C)
• The battery voltage (V)
• The battery state of charge (%)
• The maximum voltage allowed by BCM (V)
• The minimum voltage allowed by BCM (V)
• The IBS status signals
• The SAM failure status

The value of the voltage high strategy calculated by the BCM is performed by reading the following signals:

• High beams activated
• Front fog lamps activated
• Rear fog lamps activated
• The front wiper motor low or high state
• Rear wiper motor activated
• Low beams activated
• Positive Temperature Coefficient (PTC) heaters are present
• Programmable auxiliary switches are on. An equipped Power Take-Off (PTO) unit is an example of when you would find an auxiliary switch bank.
• Battery maximum charging voltage. This condition is always active.

The value of the voltage low strategy calculated by the BCM is performed by reading the following signals:

• High beams activated
• Front fog lamps activated
• Rear fog lamps activated
• The front wiper motor low or high state
• Rear wiper motor activated
• Low beams activated
• PTC heaters are present
• Programmable auxiliary switches are on. An equipped PTO unit is an example of when you would find an auxiliary switch bank.
• Requests from the Heating Ventilation and Air Conditioning (HVAC) system.