What was found
CABIN PRESSURE EXCESS CABIN ALT FOLLOWED BY CABIN PRESSURE SYS 1 FAULT AT 36,000 FT. CAB PRESS SYS 2 TRIGGER CAB PRESSURE EXCESS CABIN ALT AT 5,000 FT, 3 TIMES, DURING RETURN TO THE AIRPORT. TROUBLESHOT IAW TSM 21-31-00-810-839-A AND PERFORMED BITE TEST OF CPC. NO FAULTS FOUND. R & R OUTFLOW VALVE IAW AMM 21-31-51 AND SWAPPED CPC 1 AND CPC 2 FOR CONTINUED MONITORING IAW AMM 21-31-34. NO FAULTS OR DEFECTS NOTED AT THIS TIME.