JimF:

The IC lights remain steady and bright. (That's a great test, by the way.)


Arthur:

So, is it somehow possible the battery drain was occurring before the car was shut off? (I know it sounds odd, after all, how much power could possibly be drained from a grounded coolant sensor plug?)

Or is there some other component or wiring near/beneath that plug which, if wet, could cause a drain or otherwise trigger an ASR fault? (I vaguely recall someone writing in another ASR thread about a coolant/water leak connection to his problem.)

Edit: If there is such a component, it appears hypersensitive to moisture, considering that humidity changes will impact it.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black