I'm not sure what's causing the problem you've got with the horn, but as for the alarm, I'd highly suggest getting the alarm system professionally uninstalled, as doing it yourself can cause problems. There is a quick fix however, and it involves putting the factory alarm system in 'Valet Mode'. This will disable all security features (such as the audible alarm etc), but the central locking will still work via the key fob.
Follow these instructions:
1. Insert the key into the ignition and turn it to the 'ON' position (not "ACC").
2. Using 1 remote control, press and hold both buttons at the same time for over 2-seconds, until the status monitor's LED turns on.
** You must perform the next steps within 30-seconds **
3. Press and release the
TOP remote control button
TWICE (the chirper will chirp twice and the exterior lights will flash twice).
4. Turn the key to the 'LOCK' position (the chirper will chirp three times and the exterior lights will flash three times).
If you do not turn the key to 'LOCK', or exceed 30-seconds during the programming steps, the status monitor's LED will turn off, and the previous operation mode will remain unchanged.
If you don't want to disable the alarm and simply want to extend the 'Entry Delay Time' from 15-seconds to 30-seconds then let me know. You can also turn the 'Entry Delay Time' off completely by programming the 'Passive Arming' mode to 'off'.
Good luck!