As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE HYDRAULIC LOW PRESSURE SWITCHED ON THERE PC12/45 FLEET LEAKING EXTERNALLY. HYDRAULIC FLUID SEAMS TO BE LEAKING OUT OF THE WELDED SEAM. THIS HAS BEEN PRESENTING ITSELF AS, HYDRAULIC LIGHT COMING ON AFTER LANDING, OR A SLUGGISH HYDRAULIC SYSTEM. THE LEAK IS NOT ENOUGH TO CAUSE A HYDRAULIC FAILURE. THE PROBLEM SEEMS TO BE TIED TO BELLOW -30 DEGREES C.