I have a Honda Accord 1999 EX that i bought few months back. Suddenly a problem has cropped up.
The driver's side door does not lock / unlock when i press the remote buttons, nor when i press the buttons on the door, inside the car. Rest of the doors lock and unlock normally but not this one door.
I am a total car amateur so i am not well informed about car issues.
What may be the probable issue and what it may take to repair it?

Those car repair shops like Firestone etc will charge a lot just to check the door.
Being an amateur in this, what can i do to troubleshoot ?

 

Does the driver's door lock and unlock using the key and/or the post inside of the car?

 

From outside, the only way to unlock the door is key
From inside, the only way to unlock is to pull up the stick up. The button / **** which unlocks the door (all doors actually), will unlock all other doors except the driver's door.
It seems the signal is not reaching the stick that goes up and down to lock / unlock the door.

 

It is likely the door lock actuator. There are some YouTube videos on how to replace it.

 

I have the same problem with my rear passenger side door. I'll look into the actuator, thanks PAhonda.