[ini]

When you say that your central locking only works when you switch on the ignition, do you mean that it only works with the key in the dooor?

If you cant re-sync your remote, have you recently changed your car radio, or had the battery disconnected for a long time?

Does the alarm still arm/disarm with the remote?

Also check the central locking pump, and see if its damp or has a loose connection.