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Checking additional signals
Checking data exchange between engine, ABS, EDL and gearbox control units
Notes:
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◆ Data is exchanged between the individual control units by means of a bus system.
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◆ Bus is the term used to describe a data transfer and distribution system.
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◆ The wires between the control units along which data is transmitted are referred to as signal wires.
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◆ Data is transmitted serially along these signal wires to the connected control units (e.g. engine speed, accelerator pedal position).
Checking data wire between engine and gearbox control units
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‒ Interrogate fault memory of gearbox control unit.
=> Automatic Gearbox; Repair Group 01; Performing self-diagnosis
If a fault relating to "Data bus..." or "...communication" is displayed:
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‒ Check whether vehicle has been fitted with correct engine/ gearbox control unit. If correct control units have been fitted:
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‒ Connect up test box V.A.G. 1598/31 at wiring harness to engine control unit .
Check for short to positive/earth and open circuit in the following wiring.
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Test box V.A.G 1598/31, socket
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Automatic gearbox control unit, contact
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58
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=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
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60
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=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder
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‒ If necessary, eliminate open circuit in wiring/short circuit.
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‒ If wiring is OK, try replacing gearbox control unit or engine control unit.
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