A few days ago I was faced with two issues:

1. HDC inactive / Air Suspension Inactive + ABS lights on
2. Rough idling and CEL

I reset the vehicle (battery disconnect) and they would come back.

My investigation of the 1st, led me to disconnect and reconnect the yaw rate sensor.
The 2nd was found to be caused by a failed PCV membrane causing a vacuum leak.

Ever since I replaced the PCV, the Air Susp and HDC + ABS warnings have not come back.

As there is a vacuum hose running from the PCV to the brake master cylinder, could the failed PCV be the cause of both issues? Looks too suspicious to be just a coincidence.