I had an ABS problem ( both ABS and Traction Off lights were ON), which have been cured after contaminated brake fluid was flushed. After a week the problem is back again. When ignition is turned on, there is a hissing sound from under the hood, then there is a click and both lights go on.
What could be the problem, that changing brake fluid would solve, and then it would comes back ? Could it be a pressure modulator reservour level sensor ( this is basically the only thing which can be accessed and serviced) ? Anby ideas, experts ?