Witek,It might be time to open Owners Manual and read about Check Engine light.
That pic is direct from the 98 Owner's Manual. Didn't notice that, but i can only presume that M/B made a boo boo. And they make plenty of them, as do we all.Why in the right column of that chart does the "Battery not being charged properly"
description have an oil light next to it instead of the battery symbol?