Network Communications System Description
CAN (Controller Area Network) and the LIN (Local Interconnect Network)
The vehicle uses the CAN (Controller Area Network) and the LIN (Local Interconnect Network) as the in-vehicle LAN (Local Area Network). These networks enable the control units to exchange the information over the CAN bus. The CAN consists of the F-CAN network that enables the control units to exchange the signals regarding the power train/chassis and the B-CAN network for the signals regarding the body. These networks are inter-connected at the combination meter (gateway).

The LIN is a network for connecting the gauge control module and the battery sensor; as well as for connecting the power window master switch, the front passenger's power window switch (or each power window switches), and the moonroof control unit/motor, ensuring a reliable communication suitable for the control system. As multi-communication system between several control units, the system also provides the K-LINE and L-LINE for transmitting the diagnostic results from the HDS (Honda Diagnostic System) and the S-NET for transmitting the immobilizer signals.

CAN
The CAN (control area network) is a multi-communication system that ISO has developed and standardized for the automobile.
The CAN employs a multi-master system in which multiple control units connected to a bus communicate with each other.
Communicating Method
In the CAN, each node normally sends the digital signals in the data frame format to the bus line. As the transmitting timing, the CAN uses the cyclic sending that performs sending in a period defined beforehand, and the event sending that performs the sending only when the data is changed.
The CAN adopts the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) method in which nodes attempt to avoid collisions by transmitting only when the bus is sensed to be idle.
The digital signals are expressed as "0"(dominant) and "1" (recessive). The data frame consists of the data field (center), arbitration field for showing data ID, control field for showing data length, CRC field for detecting sending error, and the ACK field for confirming end of sending. When multiple nodes start data sending simultaneously, the CAN arbitrates them by the priority indicated in the ID in the arbitration field.
For example, when the node1 (ID=156h) and node2 (ID=164h) send the data at the same time, only the ID of the node1 is sent to the bus line because the node1 takes priority with its smaller ID. On the other hand, the node2 cancels sending the ID and being in the receiving state. After the node1 completes sending, the node2 start sending data again. That enables a simultaneous data sending from multiple nodes in a single path (multi task method).
After the data sent from a node is received by all nodes, each control unit classifies the required data by the ID and starts controlling.

F-CAN
The network between a power train and control unit for chassis system is called F-CAN and it employs high speed CAN with communication rate at 500 kbps. The F-CAN was composed of a single F-CAN Bus. To respond to the increase in the number of ECUs connected to the F-CAN and the increase in the amount of communication. The composition of the F-CAN network is divided into multiple bus lines, and an F-CAN gateway with a data-forwarding function is established, enabling the communication among the CAN Bus lines.
Connection of each control unit has control units with terminating resistor installed for preventing signal from being reflected back by a pair of twisted signal cable at each end which is comprised of F-CAN_H and F-CAN_L, with other control units in parallel connection between them. By rapidly switching between equal and unequal voltages, digital data can be transmitted in bits.
B-CAN
The network between control units for body electrical system is called B-CAN and it employs low speed CAN with communication rate at 125 kbps.
Connection of each control unit has control units with terminating resistor installed for preventing signal from being reflected back at each end of a pair of twisted wire which is comprised of B-CAN_H and B-CAN_L, with other control units in parallel connection between them.
Power Saving Mode Control
Since some control units for the body system do not stop controlling even if turned the vehicle OFF (LOCK) mode, the power-saving mode is set for these units for the purpose of reducing the dark current.
Transition to the power-saving mode (sleep mode) and returning from it (wakeup mode) are controlled by the active, sleep and wakeup signals. The control units that are not in "wait for sleep" state send periodically the active signals to the bus line and stop sending them when it is in "wait for sleep" state.
When all control units do not send the active signal anymore, one or more control units send the sleep signals. The control units that received the sleep signals go into the power-saving mode.
In the event of inputs from switch or sensor during the power-saving mode, they send the wakeup signals to the bus line. In this case, they return from the power-saving mode.

LIN
Overview
The LIN is a bus based on UART. Communication rate of LIN is slower than that of CAN, and it is used for systems for which a high speed communication is not required. It is able to reduce the wire harness bulk as well as to reduce cost thanks to its connection with each control unit with just single bus. The LIN employs a single-master system, in which only single master control unit serves as a master control unit to control all the signals on the LIN bus. Other units become slave units to serve in accordance with request from the master control unit.
This vehicle employs a LIN with a communication speed of 19,200 bps for connecting the gauge control module and the battery sensor. Some models employ a LIN with a communication speed of 9,600 bps for connecting the power window master switch, the front passenger's window switch, and the moonroof control unit/motor.
Communication System
LIN uses a single-master system, where one ECU controls all bus communication.
The other controllers act as slave units, communicating only when requested by the PCM.
The message frame is comprised of the header frame that sends the master's request and the response frame that sends the slave's response. The header frame consists of the SYNCH BREAK field for showing the frame start, SYNCH field for correcting the baud rate, and the IDENT field for showing the control unit that requests the response. The response frame consists of the data fields and the CHECK SUM field for detecting transmitting errors.

Power Saving Mode
The body electrical system has a control unit which does not stop operating when the ignition switch is off in order to perform door lock control and light control. These control units have a power saving mode to reduce the standby power requirement.
Network Communication Troubleshooting
The HDS (Honda Diagnostic System) uses the K-LINE for displaying the control unit and self-diagnostic results both in F-CAN bus and B-CAN bus. The K-LINE bus is the communication circuit that uses the UART (Universal Asynchronous Receiver Transmitter) whose baud rate is 10.4 kbps. The combination meter provides the display function for body-system DTC (Diagnostic Trouble Code). The DTC is displayed when the gauge control module receives the SCS terminal short signal via the F-CAN bus or the MICU service check ON signal via the B-CAN bus. Then, the gauge control module reads the self diagnostic results sent by each control unit via B-CAN bus, and displays the DTC.
The vehicles equipped with keyless access system, also have an L-LINE data bus that connects the data link connector (DLC) to the keyless access control unit. This line allows the HDS to communicate with the keyless access control unit if the remote are lost or malfunctioning, preventing the ignition from being switched on. The S-NET serves as a path to transmit a signal from a transponder integrated into the remote, to control units related to the immobilizer system, such as the PCM and the MICU.