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. See VAS 5051 VEHICLE DIAGNOSIS, MEASUREMENT AND INFORMATION SYSTEM, CONNECTING AND SELECTING FUNCTIONS 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
- 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 <-- 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.