Allroad Quattro V8-4.2L (BAS) (2004)
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Three or more control modules communicate through a "two-wire Bus system"
Two control modules communicate through a "two-wire Bus system"
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Switch off ignition.
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Disconnect both control modules.
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Check for open circuit in one of the Bus wires.
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations binder
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Check for short circuit in Bus wires one against the other.
Refer to Electrical Wiring Diagrams, Troubleshooting & Component Locations binder
^Check for open or short circuit to plus (B+) or to Ground (GND).
If Bus-wiring is OK:
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Replace on a trail basis the least expensive control module and the one easiest to get to.
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If the communication is still not OK, replace the second control module.
Three or more control modules communicate through a "two-wire Bus system"
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Check DTC memory of the control modules.
