It could well be the cause of the battery drain problems.
Does the alarm set normally and does it work?
If you push and hold the alarm ultrasonics defeat button with the ignition off, does the alarm lamp light solidly. Does it flash normally with the alarm set?
The Alarm ECU lives under the front passenger seat and is a victim of bad scuttle trim leaks that fill the passenger footwell with water. Not only can the box itself get it but the big wiring loom right in the footwell carries a lot of alarm wiring.
Picture of the loom here:

Shame is you have to have the passenger seat and carpet out just to check all this
Edit: I deleted your duplicate Post. Do you want this moved to the Activa area? It is OK here as it's not Activa-specific.