Definatly sounds like a wheel speed sensor and as stated, they only come with a hub/bearing assembly. Pressure washing, however; will do no good as the reluctor ring and sensor head are both behind a seal. And actually, pressure washing may penitrate the seal and get water into the bearing area. That would be bad.
Just keep in mind that you have four (4) on that car, it could be any one of them that is causing the problem. To pin point it, you need to have a scan tool that is capable of reading ABS data at a fast rate. This is obviously a "short time glitch" meaning it only malfunctions for a split second and then is back to normal. You need a scan tool that can read the data fast enough to catch a millisecond glitch.
You can try to ohm the speed sensors and compare the fronts to each other and the rears to each other, but it is not always an accurate test. And even if you find the fronts or rears are not in sync with each other, you still don't know which one is right and witch is wrong. There are no specs for this either.