What was found
(CAN) DURING CRUISE, THE FLIGHT CREW RECEIVED A YELLOW HYDRAULIC PRESSURE SYSTEM INDICATION MESSAGE. AS A PRECAUTION, WHILE TAXIING INTO THE GATE, THE FLIGHT CREW STOPPED SHORT OF THE GATE TO BE TOWED IN. TROUBLESHOOTING DISCOVERED A LEAK AT THE LOWER PTU MANIFOLD CHECK VALVE. CHECK VALVE REMOVED, REPLACED FAULTY O-RING AND CHECK VALVE REPLACED. FUNCTION CHECKS AND LEAKS CHECKS CARRIED OUT.