My alarm started "go off" within twenty minutes of locking. Key fob would not silence the alarm. Alarm would quit in about five minutes, allowing key fob to disable the alarm and unlock doors. Changed batteries in key fobs. No OBD II codes, or dash lights Nothing seemed to work.

Many years ago my auto mentor said that whenever stumped by a mechanical/electrical fault to look at what I last did to the car ("What did you last mess with.") Last thing I had done was to change a single high beam H& from OEM to LED. Wanted to see a side-by-side comparison. Incidentally, the LED is much "whiter" than OEM, and it draws less wattage too. Changed back to the OEM and the alarm problem disappeared, back to normal.

Seems that the alarm is sensitive to unauthorized removal/theft of headlights; and detects/alarms any wattage drop between the two headlight assemblies. A drop to zero would probably illuminate a dash light, whereas the partial drop just kicks on the alarm system (only when set).