I am in agreement about this issue being an intermittent problem and I was also thinking it is electrical in nature. I took off the big connector on the ABS tonight and I was really hoping to find corrosion on the contacts so I would know I found the problem. But, when I pulled the connector off everything was nice and dry and I did not see any corrosion at all. I did slide the connector on and off several times so the contacts themselves would buff the surfaces. I then sprayed both sides out with contact cleaner and put it back together.The symptoms you described do not relate to air in the system. Sounds like an intermittent so I would look at the main big connector on the ABS and look for corrosion there. Normally a wig wag of the lights at 1 hz is an indication of low fluid in the rear dual reservoir, but that usually does not lead to a loss of brake power.
I haven't had any more sensor tests fail on the GS 911, but I am getting a little frustrated with it. Everytime I hook it up it fails to read on the autoscan until I go to the K series tab and manually do a brake code read. After that I can do the autoscan. Seems like after a few reads the tester will disconnect and I have to unhook the 911 and reboot it to do any further reading. I had cleaned the contacts of the diagnostic port to make sure they were good.
@jzeiler, is this the brake bleed test you are referring to?The bleed test can be performed at any time. You really have to work at it as you squeeze the lever to keep the display in the green , centered in the marks. I usually have to use two hands for the front test and lots of foot pressure for the rear. If it passes you have no air in the system.
I haven't been able to get any readings during this test, but after rereading your post, I think I am not squeezing the brakes hard enough during the test.