run it till it runs out and then see if the light goes out, take a can of gas with you. there is a reserve of gas set below what the OBC "sees" so people dont see BMWs dead on the side of the road. I never saw mine either but also try not to ever get below an eith of a tank. I was on empty before on a run where there were no gas stations and obc was at like 5 miles when I found a station. No light yet either.
95 E34 530I V2.37
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Those who make peaceful revolution impossible will make violent revolution inevitable.
John F. Kennedy