CAN COMMUNICATION SYSTEM SYSTEM DESCRIPTION

BRIEF DESCRIPTION

1. The Control Area Network (CAN) is a serial data communication system for real time application. It is a vehicle multiplex communication system which has a high communication speed and the ability to detect malfunctions.

2. Two different types of CAN buses are used. The CAN buses are classified into two types based on typical communication speed.

   The HS-CAN bus is a high speed communication bus that is used for powertrain, chassis and some body electrical communication. The HS-CAN bus is referred to as "CAN No. 1 bus", "CAN No. 2 bus" and "power management bus" and it operates at speeds of approximately 500 kbps. Terminating resistors for the CAN No. 1 bus are located in the combination meter assembly and ECM. Terminating resistors for the CAN No. 2 bus are located in the power management control ECU and CAN No. 3 junction connector. Terminating resistors for the power management bus are located in the power management control ECU and ECM. The resistance of the CAN No. 2 bus and power management bus cannot be measured from the DLC3 connector.

   The MS-CAN bus is a medium speed communication bus that is used for body electrical communication. The MS-CAN bus is referred to as "CAN MS bus" and it operates at speeds of approximately 250 kbps. Terminating resistors for the MS-CAN bus are located in the main body ECU (driver side junction block assembly) and CAN No. 4 junction connector. The resistance of the CAN MS bus cannot be measured from the DLC3 connector.

   Communication between these networks is handled via the main body ECU (driver side junction block assembly) (for the CAN MS bus) or the power management control ECU (for the CAN No. 2 bus and power management bus), which acts as a gateway.

3. By pairing the CANH and CANL bus wires, the CAN performs communication based on differential voltage.

4. Many ECUs or sensors installed on the vehicle operate by sharing information and communicating with each other.

5. The CAN has two resistors of 120 Ω which are necessary to communicate with the main bus wire.

DEFINITION OF TERMS

1. Main bus wire

   
   

   1. The main bus wire is a wire harness between the two terminating resistors on the bus (communication wire). 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 bus wire to an ECU or sensor.

3. Terminating resistors

   
   

   1. Two resistors of 120 Ω are installed in parallel across the ends of the main bus wire. They are called terminating resistors. These resistors allow the changes of the voltage differential between the CAN bus wires to be accurately judged. To allow proper function of CAN communication, it is necessary to have both terminating resistors installed. Since the two resistors are installed in parallel, a measurement of resistance between the two CAN bus wires should produce a reading of approximately 60 Ω.

ECUS OR SENSORS WHICH COMMUNICATE THROUGH CAN COMMUNICATION SYSTEM

1. CAN No. 1 Bus

   
   

   1. ECM

   2. Main body ECU (driver side junction block assembly)

   3. Combination meter assembly

   4. Power steering ECU assembly

   5. Air conditioning amplifier assembly*3

   6. Center airbag sensor assembly

   7. Skid control ECU (brake actuator assembly)

   8. Steering angle sensor (spiral cable with sensor sub-assembly)

   9. Yaw rate and acceleration sensor

   10. AWD control ECU*1

   11. Certification ECU (smart key ECU assembly)*2

   12. Power management control ECU*2

   13. Navigation receiver assembly*7

   14. Radio and display receiver assembly*8

2. CAN No. 2 Bus

   
   

   1. AFS ECU*4

3. CAN MS Bus

   
   

   1. Main body ECU (driver side junction block assembly)

   2. Power back door ECU (back door motor unit)*5

   3. Back door closer ECU*6

   4. Outer mirror control ECU assembly (for driver side)

   5. Outer mirror control ECU assembly (for front passenger side)

   6. Position control ECU and switch assembly

4. Power Management Bus*2

   
   

   1. Air conditioning amplifier assembly*2

DIAGNOSTIC TROUBLE CODE FOR CAN COMMUNICATION SYSTEM

1. DTCs for the CAN communication system are as follows: U0073, U0100, U0101, U0123, U0124, U0126, U0129, U0131, U0142, U0155, U0164, U0182, U0199, U0200, U0208, U0230, U1002 and U1133.

TROUBLESHOOTING REMARKS

1. DTCs for the CAN communication system can be checked using the GTS. The DLC3 is connected to the CAN communication system, but no DTCs exist regarding problems in the DLC3 or the DLC3 branch wires. If there is trouble in the DLC3 or the DLC3 branch wires, ECUs on the CAN network cannot output codes to the GTS.

2. Malfunctions in the CAN buses (communication wires) can be checked by measuring the resistance between terminals of the DLC3. However, an open circuit in a branch wire other than the DLC3 branch wires cannot be checked from the DLC3.

   Note

   Do not insert the tester probes directly into the DLC3. Be sure to use service wires.

HOW TO DISTINGUISH THE CONNECTOR OF THE CAN JUNCTION CONNECTOR

1. In the CAN communication system, the shape of connectors connected to the CAN junction connector which has an earth terminal is the same. The connectors connected to the CAN junction connector can be distinguished by the colors of the bus wire and the connecting side of the junction connector.

   Tech Tips

   See Terminals of ECU for bus wire color or the shape of connectors Click here.