Description & Operation: Notes
The multiplex control system consists of a body Electronic Control Unit (ECU), driver's door ECU and front passenger's door ECU. If vehicle is equipped with driver's memory system, multiplex control system also includes a tilt/telescopic ECU. See Fig 1. Multiplex control system manages the following electrical systems in the vehicle: power window control, anti-theft system, power door lock control, wiper/washer system, outside rear view mirrors, driver's memory system, auto headlight system, illumination control and various warning buzzers. The multiplex control system is also equipped with a self-diagnostic function. Some electrical systems are directly connected to the body ECU, while some electrical loads and switches are connected to the appropriate ECU.
Vehicle body electrical systems are controlled by serial communication in which each ECU is linked together by a single communication line. Once signals are received from door lock control switch or door courtesy light switch, each ECU determines the condition of the switches and doors. Each ECU converts the signal to digital signals and then outputs them to other ECUs. The ECU that receives these digital signals then determines the conditions of the switches and doors to use various controls to operate a specific system or motor. However, if there are no changes in input signals because doors are still closed or switches are not used, the body ECU interrupts the communication to save battery power. After interruption, any changes in input signals will cause communication to resume.