Well the brake started the squeak, so its time for pads and maybe rotors. My question is with the hill hold option, when retracting the pistons can I damage this option. I use this quite a bit makes trailer pulling easer. Just not sure if there is a check valve that could be damaged.

 

Nah just do it the way you know how. Don't open any bleeder valves. The early systems were sensitive and required opening bleeders to keep old fluid from damaging the hcu. It's no longer an issue. I use a large c clamp to compress the pistons before I ever remove the caliper.