Originally Posted by xfordguy (Post 224010)

The dealer has been replacing parts as instructed by GM for nearly a month now. They can consistently reproduce the brake failure using the steps I listed above. I takes a minute or two, but they keep failing.

I have a feeling GM is buying a lemon from me very soon.

Originally Posted by evois (Post 224031)

or they don't know how to troubleshoot it. I'll see in my service manual if there is anything about it.

Originally Posted by xfordguy (Post 224271)

I got the truck back yesterday. It even stops!

The story was amusing. The GM telephone tech that was working the case went on vacation, the next guy let the dealer change the part they thought was the culprit. It was a valve that they could hear hissing when the brake was pressed. This seems to have cured the failing brake issue.

The weird thing is the brake pedal doesn't feel anything like it did before the problem. The old pedal was solid as a rock and nothing could move it down very much. Now, it feels fairly solid, but if you really stand on it, it moves down a couple inches and then stops. The pedal also goes down to the "lower position" if you are holding it when you start the truck. When the pedal is as far down as it can go, I can hear a faint buzzing sound.

Since it is possible I've had a problem since the truck was new, I have to ask "Do they all do that?".

Originally Posted by evois (Post 224273)

since the power assist(servo) brake pedal sinks a little when you start the vehicle, I'm surprised that it does it also with the hybrid since it is electric assist. so, yes they all do that.