Bought this 2006 GMC brand new in December 2005, actual mi to date 44,647.

The ABS system started with a humm 2011, with or without brakes at 9 mi an hour left front wheel. No error codes, Recently changed the pads and rotors. (NAPA)

Replaced the left front caliper, left front bearing assembly, replaced the Master Cylinder, (NAPA)

Replaced the (R) (R) dust shield, (rust through) will do the (L) (R) as time permits. Bought replacement ABS wire sensors for the front wheels and the rear dust shields from GM at Troy, New York.

Pedal goes to the floor!, checked the lines going to all four brakes, (NO LEAKS), held a 100 LBS. pressure.

From the information I'm providing, looks like this rust problem is a huge factor, that can't be ignored, the ABS system is locked in electronically as well as electrically, (60 AMP Fuse).

I shall be writing a letter to GM regarding the rear DUST SHIELDS, the salt water got into the brake system by rust through, the spring clip pin, (2ea. per wheel) (that retains the emergency brake shoe) actually rusted the end off allowing the emergency brake to come loose and caused quite a bit of noise.

My main concern is why does the brake pedal go to the floor, I have the dynamic assist, (hydraulic action behind the master cylinder, not a vacumn system).

Kenneth J Kinney