31 is your P/N switch. It'* not the problem. Nor will it affect how the car runs. 54 is EGR solonoid #2. A thorough cleaning of the EGR valve should fix this (you have the digital EGR, and many of us have seen this, cleaned the valve shafts and return springs, and fixed it).
55 concerns me. That'* a general PCM fault. Try disconnecting your battery for 30 minutes, and re-seat all your PCM connectors (PCM is above the RF passenger footwell). See if the 55 comes back.
Where are you located? Can you put your location in your profile, and put "93 SSEi" in your signature? Both of these will help us to help you.