It most likely could be the door lock relay behind the glove box that is at fault. You can take a chance and replace it, or you can use the diagram below to test it but you need a volt/ohm meter to do it. If you have further questions feel free to reply.
Hopefully you tested the circuit like i advised.
Let me know!
Sorry for the delay. A common thing that happens is the wires that go to the switch on driver door get broken from the door opening and closing after time. If you open the door and look in the hinge area, you will see the wire loom that i'm referring to. It will need to be opened up and the wires tested for continuity.
Click on the image below, then print it out.