u/New_Sega

My wife walked outside this morning and saw her 03 Honda Odyssey running without the keys in the ignition. The radio and stuff wasn’t on but the motor was definitely running. The only way I could turn it off was by disconnecting the negative battery terminal.
It did have one of those aftermarket alarm systems on it when I bought it but it looks professionally installed. Any idea what could be causing this? I’ve found almost nothing online about it.
Thanks!