Checking bus system

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2003 Audi S8, 2003 Audi A8, 2002 Audi S8, 2002 Audi A8, and 2001 Audi S8. However, it is still accessible from the selected car via links, so may be relevant.

The DTC table indicated that data exchange via the bus should be checked:

Check to be sure the multi-pin connectors of the control modules are securely connected.
Connect the VAS 5051 tester or VAG 1551 scan tool. See VAS 5051 TESTER OR VAG 1551 SCAN TOOL, CONNECTING AND SELECTING FUNCTIONS .
Switch ignition on
Switch printer on via the PRINT button (indicator lamp in button lights up).
Press button 1 to select "Rapid data transfer" operating mode 1.

Indicated on display

Fig 1: V.A.G 1551 Scan Tool Display - Checking Bus System (1 Of 2)

Courtesy of AUDI OF AMERICA, INC.

NOTE: The address word 00 initiates the automatic test sequence, i.e. it results in a DTC check on all OBD capable systems in the vehicle via rapid data transfer.

When a control module responds with its identification, the display indicates the number of stored DTCs or indicates "no malfunctions recognized."

DTCs stored in the system are indicated sequence and printed out. Then the VAG 1551 scan tool sends the next address word.

Automatic test sequence is over when the following indication appears on the display:

Fig 2: V.A.G 1551 Scan Tool Display - Checking Bus System (2 Of 2)

Courtesy of AUDI OF AMERICA, INC.

If a malfunction involving" ... databus" or" ... no communication" is indicated:

Check whether the correct control module for this vehicle is installed (part number and coding).

If the correct control modules are installed, check the CAN bus system.