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Three or more control units communicating via a "two-wire bus system" > < Checking a "two-wire bus system"

A3 Mk1

Two control units communicating via a „two-wire bus system“
   
Two control units communicating via a „two-wire bus system“
–  Switch off ignition.
–  Detach the multi-pin connectors at both control units.
–  Check whether there is an open circuit in one of the bus wires → Current flow diagrams, Electrical fault finding and Fitting locations.
  A01-0024
–  Check whether there is a short circuit between the bus wires → Current flow diagrams, Electrical fault finding and Fitting locations.
  A01-0025
–  Check whether there is a short to positive or short to earth in one of the bus wires.
If no fault is detected in the bus wires:
–  As a trial measure, renew whichever control unit is easier (or less expensive) to change.
If the control units are still not communicating via the bus:
–  Renew the second control unit.
  A01-0026

Three or more control units communicating via a "two-wire bus system" > < Checking a "two-wire bus system"