Island Hopper

If the engine goes into Guardian mode, it will lock in the fault, in fault history, until cleared. If there is nothing in the fault history, you may have another problem. At any time a fault occurs you should get an audible warning, either a constant horn, or a 1 beep per minute, depending on the severity of the fault. There are to many things that can cause these kind of problems without using a scan tool. It sounds like a guardian issue, but not getting an audible warning, is odd.