Check engine light came on last week. (2000 X5 4.4)

I reset the light when I had to reset the battery (disconnect for 10 mins).

After about 50 miles its back on. I used a Launch Creader (cheapy obdii) reader and cannot get any codes.

Any ideas... I guess maybe I'll stop by the auto parts store and have them scan it.

Is there ever a case when the check engine light comes on with no codes?

I do have to replace my Final Stage Resistor...its on order. I've noticed the fan runs for a while -- keeps going all night... when the car is off.

Would the final stage resistor cause any wierd check engine lights???

Thanks