If you cannot determine a cause for the malfunction, e.g. "power train data-BUS faulty", check whether one of the control modules may be responsible for the DTC

All control modules that use the CAN-bus are still disconnected. Ignition is switched off.

• Connect one of the control modules.
• Connect VAG 1551 scan tool. Switch ignition on, and erase the DTC memory of the control module you just connected. End scan tool output using the "End Output" function 06.
• Switch ignition off and then on.
• Leave ignition on for 10 seconds. Then, read the DTC memory of the control module you just connected.
• If the DTC "power train data-BUS faulty" is displayed, replace the control module you just connected.
• If the DTC "power train data-BUS faulty" is not displayed, connect the next control module and repeat the procedure.