i had the same symptoms with my EBCM. it would come and go.
but one way to find out is... go to a cheap shop that charges like $30-60 bucks for an ABS scan. let them scan it. if they say "oh man we can't find ANYTHING wrong and our scanner won't read anything and the wiring is good" then your EBCM is bad and you don't have to pay anything because their scanner didn't give results (or at least u better not pay).
so yeah. i however went to the dealership just to be sure and paid $100 for one of their scans but im a perfectionist i like it to be clear-cut defined problems.