I cant use the switch to unlock the doors?

Electrical problem
1999 Honda Civic Two Wheel Drive

I have notice others with the same problem as me. The automatic door locks dont work any more. I have heard it could be the auctuater or the control module. Has any one heard about having to reprogram the computer to get them working again?
And how do I determine what is the problem without spending a ton of money? Would it have any connection with upgrading the stereo?

The power locks on my '98 Honda Civic work only on the driver's side door, the remaining 3 doors dont show any response. What could be the problem?

Thanks for your reply, your answers sounds like the correct one. I checked it when I got a chance, the wires seem to be tight and intact. Since it's a big coupling with lot of wires and it's short in length it was really hard to check them in detail. Do you know a way to check couplings like this? Can you suggest a way to proceed once I have the couplings separated?

Thanks a lot. The control unit is in the door panel. I'll check it like you said and I'll let you know what happened. Thanks :)