System Description

1. The CAN (Controller Area Network) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed (500 kbps, 250 kbps) and the ability to detect malfunctions.
2. By pairing the CANH and CANL bus lines, the CAN performs communication based on differential voltages.
3. Many ECUs (sensors) installed on the vehicle operate by sharing information and communicating with each other.
4. The CAN has 2 resistors of 120 Ω which are necessary to communicate with the main wire.

1. Main wire
   1. The main wire is a wire harness between the 2 termination circuits on the bus (communication line). This is the main bus in the CAN communication system.
2. Branch wire
   1. The branch wire is a wire harness which diverges from the main wire to an ECU or sensor.
3. Termination circuits
   1. The termination circuits is a circuit which converts the communication current of the CAN communication into the bus voltage. It consists of a resistor and condenser. Two termination circuits are necessary on a bus.
4. CAN J/C
   1. The CAN J/C is designed so that it can be used with CAN communication which has a termination circuit and CAN communication which does not have a termination circuit.

1. The V bus and MS bus each have termination circuits with 120 Ω x 2 of resistance. High speed communication at 500 kbps and 250 kbps is possible.

HINT:

• *1: w/ Bus Buffer ECU
• *2: w/ 4WD
• *3: w/ Seat Memory

1. ECM
2. Skid control ECU with actuator
3. Combination meter ECU
4. Center airbag sensor
5. Air conditioning amplifier
6. Steering angle sensor
7. Bus buffer ECU*1
8. 4WD control ECU*2
9. Main body ECU
10. Front power seat ECU and switch LH*3
11. Outer mirror control ECU*3
12. Multiplex tilt and telescopic ECU*3

1. DTCs for the CAN communication system are as follows: U0073, U0100, U0101, U0114, U0123, U0124, U0126, U0129, U0199, U0208, U1002, U1115, B1499, and B2621

1. Trouble in the CAN bus (communication line) can be checked through the DLC3 (except when there is a wire break other than in the branch wire of the DLC3).
   NOTE: Do not connect the tester directly to the DLC3 connector. Be sure to use a service wire.
2. DTCs regarding the CAN communication system can be checked using the intelligent tester.
3. The CAN communication system cannot detect trouble in the branch line of the DLC3 even though the DLC3 is also connected to the CAN communication system.

1. In the CAN communication system, the shape of all connectors connected to the CAN J/C is the same. The connectors connected to the CAN J/C can be distinguished by the colors of the bus line and the connecting side of the connector.

   HINT:

   See TERMINALS OF ECU  for bus line color or the type of connecting surface.