A failing battery can cause any number of warning lights to come on. Replace the battery if necessary. Then see if the warning lights are still there. Until then, don't worry about the warning light.

If the battery is 4 or more years old, just replace it. It doesn't have to be a BMW battery, but it has to physically fit, have sufficient reserve capacity, and have the external vent tube (since it is under the floor). Search on battery replacement posts for recommendations on specific battery suppliers.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue