B-CAN System Description
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.
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||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.
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.
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.