don't start, battery good, it was running great, no lights on on 2003 BMW 325xi

it was running great . all of a sudden didnt start, battery is good and no dashboard lights on

Asked by for the 2003 BMW 325xi
If is cranking over then have to start with basics and see what is missing when turning engine over---spark or fuel and go from there.
1 more answer
Take to dealer and reset the ECU it's a security thing with BMW cost bout 110.00.