ABS light keeps burning

Hello everyone,

I hope someone can help me out.
The abs light keeps burning on the dashboard. when i push the abs switch nothing happend, when i push it again the abs light blinks 1 time (means there`s a problem)
I measured the wheel sensors and they are ok, it must be something else because the light burns as soon i start the car, and i haven`t drive yet

Can someone help me out?

Many thanks,

Emil