What was found
GEG FLIGHT NR 2356: UPON DESCENT INTO GEG, ENTERED CLOUDS WITH ICE. TURNED ON AIRFRAME ANTI-ICE TO SLOW POSITION. THE DEICE PRESSURE CAUTION LIGHT ILLUMINATED IMMEDIATELY. RAN THE CHECKLIST. PROBLEM WAS FIXED FOR APPROXIMATELY 30 SECONDS AFTER RE-SELECTION OF SLOW THEN THE DEICE PRESSURE CAUTION LIGHT ILLUMINATED. PRESSURE GAGE APPEARED TO HAVE NORMAL PRESSURE. MAINTENANCE REMOVED AND REPLACED NR 2 DDV VALVE IAW Q400 AMM 30-11-16, PGS 401-408. OPS CHECK GOOD. REMOVED AND INSTALLED LEADING EDGE 613AR IAW AMM TASKS 57-23-01-000-801 AND 57-23-01-400-801. AIRCRAFT RETURNED TO SERVICE.