As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) WHILE COMPLETING THE DE-ICE PRESSURE REGULATOR FUNCTION CHECK THE WING DE-ICE ISOLATION VALVE WAS FOUND TO BE LEAKING (NOT CLOSING COMPLETELY) ALLOWING AIR PRESSURE TO BOTH WINGS. TWO OTHER ISOLATION VALVES WERE FUNCTION CHECKED AND WERE ALSO FOUND NOT CLOSING COMPLETELY.