I'm not going to pretend I know how the whole system works and yes I agree there is a brake master cylinder that does provide braking when this happens. However, when it does happen you are expecting to apply the brakes like normal and suddenly they go almost all the way to the floor while providing NO braking during during all that travel to within about an inch of the floor. All this while almost every warning annunciator on the instrument panel is illuminating to tell you you have a brake failure. So yes I can still stop but that stopping is not assisted by all the normal means when it happens. And most every warning annunciator on the instrument panel coming on as well as warning chimes sounding can be somewhat distracting.

 

If its electrical, there should have been an error. I have 163k miles now and have not noticed that happened to me at all.

 

Trust me, there is no way to not notice when it happens. Like I said warning annunciators are all lit up, the warning chime is sounding, the pedal goes almost all the way to the floor. Can't help but notice when it happens. Perhaps it was worked out on the 2009 models. C12B1, C0110, C0277, C12E0 were the codes they captured. I'm glad you have never had the problem Jeremy. However for those of us that have had it, it is frightening.

 

Well if there are codes then that should make it easy to fix? I know how it feels to lose brakes and depend on the dual fail safe mode.

 

There used to be a poster on here that was extremely condescending and suggest that people posted this problem as a way to attempt to get out of their new car contract they couldn't afford. Having bought a reasonably priced used hybrid I don't have that problem. But I'm sure I have figured out why someone traded this one in. By the way... I love my yukon. Just wishing it didn't have intermittent brake failures.

 

The codes didn't seem to tell them for sure what the problem was. The dealer went to tech support and verified I had the latest software. I think I'm going to throw the $500 master cylinder at it like they suggested and hope that cures it.

 

So of it's master cylinder, it is totally unrelated to the electric braking. If its the MC the brake fluid rises up the MC assembly instead of lowering.

 

Kind of my point. I don't believe it's the master cylinder.

 

Very scary..I wondering if this is a issue that shows up right from the beheld or as the truck ages?

 

Yep. Scary. I just walked out to it, started it, stepped on the brake and this is what I got
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