How do you disable alarm without the remote on 2004 Honda odyssey?

To disable the alarm on a 2004 Honda Odyssey without the remote, insert the key into the driver's side door lock and turn it to the unlock position. This should deactivate the alarm system. If that doesn't work, you can also try starting the engine with the key, which may reset the alarm. If the alarm continues to sound, disconnecting the car battery for a few minutes may help reset the system.