does anybody solve that problem?

I have same problem in 2008 fiesta st. diagnostic code is U100. today I touched front abs sensors, and problem has gone. but later same day, I swap my rims and now again same error.

So it can be front abs sensors, abs module.. what else? How to be sure module has gone (or sensors)? because there is just one error code u1900 which doesnt tell me what exactly has gone