Checking Bus System

Checking bus system
In the DTC table you were instructed to inspect the exchange of data between the Transmission Control Module (TCM) and CAN-capable control modules.
- Connect VAS 5051 Vehicle Diagnosis, Measurement and Information System and select vehicle system "02 transmission Electronics". Ignition must be switched on.





Display on VAS 5051
- Touch -1- diagnostic function "08 Read Measured Value Block".





Display on VAS 5051
1 - Enter display group Max. input value = 255

Note: Measured Value Block 125 shows the participants on the data BUS drive.

- On keypad enter -2- '125" for "Display group number 125" and confirm by touching Q button.





Display on VAS 5051





- Check displays in display fields -1- to -4-.
- The display shows the control modules which are CAN- capable with the Engine Control Module (ECM):
^ Display 1: CAN-capable control module is a participant on data bus
^ Display 0 or no display: CAN-capable control module is not a participant on data bus or not CAN-capable
- End function "08 Read Measured Value Block" by touching 4 button.
- Touch "06 End output'.

Display on VAS 5051
- In selection -1- touch diagnostic function "00 Read DTC memory complete system".
^ DTC memory of all systems in the vehicle capable of On Board Diagnostic (OBD) is read.
If a control module responds and identifies itself, the number of stored DTCs or "No DTC" is displayed on the screen.
Any stored DTCs in a system are shown in sequence. Then the VAS 5051 sends the next address word.
If a DTC referring to "Data bus drive..." or "...CAN bus" is displayed:
- Check whether correct Engine Control Module (ECM) and other CAN-capable control modules have been installed (Part No. and Code).
If the correct control modules have been installed
- Check whether multiple connectors for control module are fully seated.
If the multiple connectors are fully seated:
- Check CAN bus system.