2004 Toyota Corolla with 210k kms. Up until few weeks central locking worked fine but now only three doors get locked/unlocked using the key. The driver door get lock and get unlock instantly. The door can be locked/unlocked manually. How can I fix this?
How can I fix this?
Find the fault and fix it.
It's a little hard to tell exactly what's going on from your description. Is it that the lock on the driver's door is not working and the other 3 are? If so, you might just find that after 20 years of opening and closing the driver's door that the wiring has failed due to all that flexing. Or the motivator inside the door that operates the lock mechanism may have failed. To get at that you have to remove inside the door panel.
is it that the lock on the driver's door is not working and the other 3 are? YES
Then get out a test light or voltmeter and trace out the wiring until you find the fault. If you examine the wiring between the door and door jamb you might even see physical damage from flexing.