Description & Operation: Notes
The multiplex control system is a Local Area Network (LAN) to manage the operation of numerous body electrical systems. This LAN consists of a Body Control Module (BCM), 5 Local Control Units (LCUs) and is connected to power window, power door lock, rear defogger, wiper/washer and multi-remote control systems, in addition to various illumination, warning and buzzer circuits.
Some electrical systems are directly connected and controlled by the BCM, while some switches and electrical loads are controlled by an appointed LCU. The BCM is the master unit of the LAN and has communication and control functions over the LCUs via multiplex data lines (A1 and A2). See Fig 1 . Commands may be directly sent to electrical systems controlled by the BCM, or indirectly controlled by the LCUs. The LCUs receive commands for the operation of certain switches or electrical systems, and can also send switch signals back to BCM.
System has sleep/wake-up control modes. Sleep control mode prevents unnecessary power consumption by suspending communications between BCM and LCUs, under certain conditions. Wake up mode returns BCM to normal control when a "wake-up" signal is detected. Also, if BCM determines that a circuit or system of an LCU is malfunctioning, multiplex control system will place affected LCUs into fail-safe control mode. In the fail-safe control mode, no electrical loads for an affected LCU will be commanded from BCM.