This has been discussed at length many times before, but I havent read a definitive answer to it.
THESE are just some of the relevant threads. It is a lot of reading, perhaps someone can recall a thread with a definitive answer
an interesting
THREAD HERE and
ANOTHER
I can see how the ABS unit could become involved in a sinking/spongy pedal, but cannot understand how just having the ignition on will eliminate it from the symptoms. To elinimate it, I would have thought the ABS would need to be activated (ie that pumping feeling you get when brakes are pressed in an emergency stop situation)
