Do you mean the Check Engine light? You need a code reader to identify the problem, try posting on the regular E36 forum and give a little more details of the issue, maybe you'll have more answers.

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"If everything seems under control, you're just not going fast enough"
-Mario Andretti.
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River City Bimmers Chapter
2005 X3 3.0i ZPP, Htd seats, Htd strng, Black Sapphire on Terracotta.
1995 ///M3 Coupe, Lux, MT, Htd seats, Cosmos Black on Black.