Why will my Kia Optima power door lock button lock the doors but not unlock the doors?
Great question--I came here looking for an answer! I have the same problem. The Drive's door will not unlock--not with the power fob, not with the key on the outside, not with the door handle on the inside. I'm surprised someone from Kia has not addressed this.
We took the car to the local Kia dealership where we had purchased the car new, and the shop told us that it was a faulty door lock actuator. The mechanic did not open the door, but said that this was a common problem. They estimated $200 plus labor to repair.
This weekend, I decided to open the door and look for myself. What I found is that the actuator was fine.
The fault was with the latch mechanism, called "door checker" in the Kia service manual. Not the lock... the latch; the actual part that latches onto the striker when the door is closed.
To determine the fault, I first removed the door panel. Remove 1 screw in the grab handle pocket, 1 behind the door open lever, and 2 screws at the forward edge, the bottom edge, and the rear edge. Remove the small window-corner speaker if equipped. Then lift off the door panel. Don't lift too far, there are wires to disconnect.
Once the door panel was removed, I removed the exterior door handle. Two bolts on the inside of the door secure it. Use 10mm socket to remove them. Then remove the connecting linkages by flipping the plastic catches on each to the side. This should allow you to pop the linkage from the socket. The heavy linkage is a little harder, as it has a locking groove. You may need a jewelers screwdriver or dental picks to open the plastic socket a little. Be very careful not to get forceful or you risk breaking the plastic catch. The actual lock mechanism turns 1/8 turn and slides out of the handle assembly. Set the handle aside.
Now disconnect the linkage from the actuator, again by flipping the plastic catch to one side and slipping the linkage from the socket.
Finally, disconnect the linkage that goes to the interior lock above the door-open handle.
With these linkages disconnected and the door handle out, remove the plastic cover on the latch mechanism. You should now be able to peer in and work the lock and opening levers independently and find the fault.
On my particular latch, the plastic bits (yes, they used plastic) had worn and become loose. This allowed the rotating part of the latch to rotate too far, which in turn caused a bind when you try to unlock the mechanism. The security system senses that the latch is not properly unlocked, causing the actuator to immediately engage and relock the doors.
If you confirm that this is your problem, then remove the three screws that hold the mechanism in place and replace the mechanism. I obtained mine from a salvage yard for $30.
Total time to diagnose and repair was about 3 hours - but you now will have an advantage in knowing what you're looking for!
Kia Dealer in Pittsburgh wants $42.00 for "Car Checker" part. Give them your model/year and last eight digits of your vin number when you call to order "door checker" part.