Determining Fault In Comfort Data Bus System

Comfort Data Bus System, Checking

• If the connector is disconnected from a control module connected to the comfort data bus system and the ignition is switched on, a fault entry can occur in the other control modules connected to the comfort data bus system. The same is true if the voltage supply is interrupted by activation of a fuse for example.

• The instrument cluster control module (J285) forms the interface between the two data bus systems. It is also the determining control module in the comfort data bus system. Via adaptation the control modules connected to the comfort data bus system in this vehicle are entered (equipment-dependent). Refer to => Vehicle Diagnosis, Testing and Information System VAS 5051 in the "guided fault finding" function.

• The wiring diagrams can be used to determine how many control modules are connected to the comfort data bus system.

Determining Fault in Comfort Data Bus System

- Connect the Vehicle Diagnosis, Testing and Information System (VAS 5051A) e.g. via the diagnostic cable (VAS 5051/5A) and the K-wire adapter ( VAS 6017B), or in vehicles up to VIN "399999" of model year 2005 (Sedan and Avant) and "012913" of model year 2005 (Cabrio) via the K-wire adapter (VAS 6017A ) to the vehicle's 16-pin data link connector with the ignition off. Refer to => [ VAS 5051A, Connecting and Selecting Functions ] VAS 5051A, Connecting and Selecting Functions.

- Switch the ignition on.

- Select the "00 - query the DTC memory - entire system" function.

Indication on display of the Vehicle Diagnosis, Testing and Information System (VAS 5051A):





All address words stored in the Vehicle Diagnosis, Testing and Information System (VAS 5051A) are transmitted consecutively via the data line to the vehicle

Indication on display of the Vehicle Diagnosis, Testing and Information System (VAS 5051A):





• Display field - 1 - shows which address word is currently being transmitted by the Vehicle Diagnosis, Testing and Information System (VAS 5051A).

• Display field - 2 - shows which control modules responded. In addition, the number and type of faults stored in this control module are displayed.

- Wait until "function finished" appears in display field - 1 -.

• If another or additional fault is stored in a control module with which the other control modules do not exchange data, correct this fault before checking the data bus wire system.

• A fault in a control module can disrupt data exchange with the other control modules even though this error does not directly affect the data bus system.

• Check the part number with the associated index of the control module with which no communication is possible.