ABS actuator question
 

I have a non mercedes technical question. it's regarding a lexus ls400. I've done extensive research and concluded that a faulty / sticking dump valve inside the ABS actuator could also be the root cause of a spongy pedal.
I would like to get the technical opinion whether that could be the case or not.
lexus uses nippondenso ABS system which I guess is different than what mercedes uses. is it BOSCH ?
but then again the mechanism are quite similiar hence my reason for posting this question here.