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Checking auxiliary signals
Testing crash signal
The engine control unit receives the crash signal ("Crash cut-off was activated") from the airbag control unit.
If the airbag control unit sends the crash signal to the engine control unit (during an accident or if a final control diagnosis relating to the airbag system is carried out), the engine control unit switches off the fuel pump, which stops the engine. It can however be restarted (e.g. to move vehicle out of danger area)
The engine control unit is unable to switch off the fuel pump in the case of an accident involving activation of airbag when the fault entry "Crash signal from airbag control unit, implausible signal" exists, because the engine control unit is unable to recognise the crash signal from the airbag control unit; e.g. due to a wiring problem between engine control unit and airbag control unit.
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‒ Connect the V.A.G 1598/31 test box to wiring harness leading to engine control unit; the engine control unit should not be connected .
Check the following wiring connections for open circuit and short circuit to positive or earth.
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Test box V.A.G 1598/31, Socket
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Airbag control unit, Contact
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67
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=> Current Flow Diagrams, Electrical Fault-Finding and Fitting Locations
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- Wire resistance: max. 1.5 Ohm
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‒ Rectify any open/short circuit as necessary.
=> Current Flow Diagrams, Electrical Fault-Finding and Fitting Locations
If no wiring fault is detected: Interrogate the fault memory of the airbag control unit.
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