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- -> Disconnect the control units which are linked by the bus wires and check for a short circuit between the
bus wires
=> Current flow diagrams, Electrical fault finding and Fitting locations binder
- -> Check the bus wires for short to positive and short to earth.
If the cause of the fault "Data bus drive defective" cannot be found in the data bus wires, check whether one
of the control units is causing the fault.
At this stage all the control units which communicate via the CAN data bus are disconnected. The ignition is
switched off.
- Connect one of the control units.
- Connect fault reader V.A.G 1551. Switch on the ignition and erase the fault memory of the control unit which
has just been connected. End output from fault reader with function 06 "End output".
- Switch the ignition off and then on again.
- Leave the ignition switched on for 10 seconds. Then interrogate the fault memory of the control unit that has
just been connected, using the fault reader.
- If the fault "Data bus drive defective" is now indicated, replace the control unit which has just been connected.
- If the fault "Data bus drive defective" is not indicated, connect the next control unit, and repeat the above
procedure.
Audi A8 1994 ➤
Motronic injection and ignition system (6-cylinder) - Edition 02.1999
8.4 - Testing data exchange between control units
93
