Brake and 4x4 warning on 2004 BMW X3

brake and 4x4 warning lights came on while driving. No change in driveability or braking, and the car is making no noises. Possible causes?

Asked by for the 2004 BMW X3
hold the button that reads u have a flat for more than 20 seconds should help
1 more answer , 1 more comment
Is the ABS light also on? That should indicate a ABS / Trac control problem, maybe a lost wheel speed sensor signal. To figure out for sure it has to be diagnosed with an OE or similar diagnostic computer.

No, the ABS light is not on. I had brakes and rotors replaced within the last two months, so I am thinking wheel speed sensor. The lights went off yesterday and have not returned, so I am thinking this is definitely just a sensor. Thanks for the answer!