If you watch the IT Mercenary video I linked to above, from 12:57 to 13:08 in the video, he is getting ready to active the ABS. Keep in mind, he has already performed a brake fluid flush beforehand.

At this point in the video, he is walking through the procedure to activate the ABS HCU. His exact words are "...we'll hear the ABS HCU unit do its magic and we'll be done with the front other than we'll have to flush it one more time manually and call it a day."

Apparently, any old fluid that didn't get flushed and which remained in the HCU during the initial flush procedure is "mixed" with the new fluid when the HCU is activated. After the final flush, the so-called contaminated fluid is replaced with new fluid, but I have to believe the fluid that is in the HCU is not 100% clean brake fluid.

This is just my interpretation of what I'm understanding and seeing in the video. Others are free to disagree with me.

 

You can purchase additional licenses.

 

That is basically correct.... but forever is a very long time...

The module has to be activated, to move fluid from the module into the rest of the brake system.... That is what the various tools do, as well as activating it during a ride.... but to reliably, and most efficiently, "flush" the fluid from the module, the various tools are the way to go..

When the ABS light comes on with every key "on" sequence and does a self check... it's just cheking the electronics of the system... it doesn't function test the module.. That's why when the free brake flush campaign was in full swing... people were going to the dealer only to find their ABS modules were bad (frozen up)... Their modules had never been "exercised"..

 

Sorry, just came back and re-read this. Yes the fluid would stay in the pump and I believe it was a reason for ABS failure on some bikes.

https://www.consumerreports.org/reca...%20replacement.

 

I have the Diag4bike tool, the equivalent aftermarket of the HD digital technician.
When I bleed the ABS the brake lever goes first fully in as if there was air, then it push back midway back and start pulsing for about 30 sec with the ABS unit pumping as hell. As it finish it does the same with the rear brake.
A warning on the screen advise not to repeat the procedure for a time (don’t remember now the value) in order to avoid overheating the ABS unit.
I don’t think that activating the ABS repeatedly while riding can get the same result.
In theory, without a flush the ABS unit could hold the old oil forever if never activated.

 

I bleed my system with the Daytona twin scan 4. Abs units get damaged when old brake fluid kept within the unit gets moisture as all dot 4 fluid ages which can potentially damage the seals inside the units. I bled every other year.