Alarm system issue

A friend of mine is having issues with her 03 Tacoma. Last night her alarm went off so she went down to check it out. Turned the alarm off and re-activated the alarm. About 20 seconds later the alarm went off again. She said she unlocked it, climbed in and started the truck. The warning lights (check engine etc.) are now flashing even with the truck off and no alarm activated.

My best guess is water, at least a little moisture (it rained last night), somehow got into the ECU or some other component of the alarm. Or possible corrosion on a wire or connection. Does that sound like the right direction to go with trouble shooting this issue? If anyone has any experience with this please respond. I downloaded a manual for the alarm…I’m assuming it’s an RS3000….

Thanks

02 tacoma 2.7 will start and run about 3 seconds then die wont start again until key is turned off then back on. will only run 3seconds and die it is loseing injector pulse fire is still at injectors but ground dont pulse