Which year? Have you opened the connector in the door jam to see if there is water and corrosion in the pins? A lot of us have water but not many problems, I loaded my connector with dielectric grease. Only Locking?
On a 2007 Outlook it Looks like there is one main relay which locks all doors and two relays for unlock, one for drivers door and the other for the other three.
I believe there is one Lock Relay for all doors on that year as well. Either you have a connection problem from the relay or both lock coils are defective. Try opening the connector in the door jam to see whats the condition.