Steve - I don't know how the IC knows when to turn those lights on.

This is a bit out of my league, but based on your wiring diagram it looks like CAN C high (rd/br wire) is either disconnected or the signal is faulty.

Does this agree with your analysis?

Thanks for your help!!

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE