Checking A "Dual Wire Bus System

Checking a "Dual Wire Bus System"
Communication takes place between two or more control modules over a "Dual Wire Bus System".
- Analyze DTCs stored in control modules.

Note: The analysis helps to pinpoint the wiring malfunction.





Example 1:
Based on the DTCs entered in the DTC memories, it can be seen that control module 1 is not connected to control modules 2 and 3.
- Switch ignition OFF.
- Disconnect control modules connected by bus circuit and check whether a bus wiring connection has an open circuit.
Refer to wiring diagram
- If no malfunction is found in bus wiring, replace control module 1.





Example 2:
- Based on the DTCs entered in the DTC memories, it can be seen that control module 2 is not connected to control modules 1 and 3.
- Switch ignition OFF.
- Disconnect control modules connected by the bus circuit and check whether a bus wiring connection has an open circuit.
Refer to wiring diagram
- If no malfunction is found in bus wiring, replace control module 2.





Example 3:
Based on the DTCs entered in the DTC memory, it can be seen that no transmission or reception activity is possible in any of the control modules.
- Switch ignition OFF.





- Disconnect control modules connected by bus circuit wiring and inspect bus wiring for a short circuit to B+ and to ground.
Refer to wiring diagram

If you are unable to determine any cause in the bus wiring for the DTC "Data bus drive faulty", check to see whether one of the control modules is responsible for this DTC.

Test requirement:
^ VAS 5051 Vehicle Diagnosis, Measurement and Information System connected and Vehicle OBD selected.
All the control modules which use the CAN bus for communication are disconnected. The ignition is switched OFF.
- Connect one control module.





Display on VAS 5051
^ Switch ignition ON.
^ Touch appropriate vehicle system in Display -1-.
^ Read DTC memory of control module just connected and delete it.
^ Touch 01 button.
^ In display touch -1- diagnostic function "06 End output".
^ Switch ignition OFF and ON again.
^ Leave ignition switched ON for 10 seconds. Then, using scan tool, read DTC memory of control module just connected.
^ If DTC "Data bus drive faulty" is read, control module just connected must be replaced.
^ If DTC "Data bus drive not faulty" is read, connect next control module and repeat procedure.