B-CAN System Description

B-CAN


The B-CAN (Body Controller Area Network) uses a single wire method for communication between the gauge control (tach) module, MICU, climate control unit and immobilizer-keyless control unit. B-CAN communication moves at a slower speed (33.33 kbps) than F-CAN (500 kbps) for convenience related items and for other functions.

 

  • The single wire method is used between the units not requring the communication to move at a fast speed.
  • Using a single wire method reduces the number of the wires used on the body controller area network.

Gateway Function


The gauge control module (tach) acts as a gateway to allow both systems to share information, the gauge control module translates information from B-CAN to F-CAN and from F-CAN to B-CAN.

 


Network ‘‘Loss of Communication'' Error Checking Function


The ECUs on the CAN circuit send messages to each other. If there is any malfunction on the network, the odo/trip display on the gauge control module (tach) can indicate the error messages by entering the gauge self-diagnostic function.

Error Code List
Error code Type of communication line(s) error 
Error 1 F-CAN communication 
Error 2 B-CAN communication 
Error 3 UART communication 
Error 12 F-CAN and B-CAN communication 
Error 13 F-CAN and UART communication 
Error 23 B-CAN and UART communication 
Error 123 F-CAN, B-CAN and UART communication 

NOTE: For further information about Error indication, refer to the gauge control module self-diagnostic function.

 

Wake-up and Sleep Function


The multiplex control system has ‘‘wake-up'' and ‘‘sleep'' functions to decrease the parasitic draw on the battery when the ignition switch is OFF.

  • In the sleep mode, the MICU stops functioning (communication and CPU control) when it is not necessary for the system to operate.
  • As soon as any operation is requested (for example, a door is unlocked), the related control unit the sleep mode immediately wakes up and begins to function.
  • When the ignition switch is turned OFF, and the driver's door is opened, then closed, there is a delay of about 40 seconds before the control unit goes from the wake-up mode to the sleep mode.
  • The sleep mode will not function if any door is opened or if a ignition switch is in the ignition.
  • The draw is reduced from 200 mA to less than 35 mA when in the sleep mode.

Fail-safe Function


To prevent improper operation, the MICU has a fail-safe function. In the fail-safe mode, the output signal is fixed when any part of the system malfunctions (for example, a faulty control unit or communication line).
Each control unit has a hardware fail-safe function that fixes the output signal when there is a CPU malfunction, and a software fail-safe function that ignores the signal from a control unit, which allows the system to operate normally.

NOTE: Sleep and Wake-up Mode Test.

Self-diagnostic Function


By connecting the HDS to the data link connector (DLC), the HDS can retrieve and indicate the diagnostic results of each ECU. The diagnostic line called K-LINE is distinguished from the CAN line, and connected to the all CAN related ECUs. The MICU is a gateway between the HDS and B-CAN related ECUs, and sends B-CAN diagnostic results to the HDS. When performing a function test with the HDS, the HDS sends an output signal through the K-LINE to the MICU. The MICU either relays the request to another ECU, or commands the function it's self.