There has been a pretty good picture of the can bus posted somewhere on here. AFAIK the physical bus is not daisy chained but the data flow can be. One module might be depended on passing information to another so you possibly could loose the information from more than 1 module by disconnecting only one. Disconnecting should still give you your answer though on which module is pulling down the bus.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)