The OEM alarm, once off doesn't go off for any reason unless it reactivated itself due to not opening the driver's door when unlocking the car via the remote within 15 seconds. It doesn't have a motion sensor, only current sensor.
Therfeore, you must have an aftermarket alarm... it must have a motion sensor mounted somewhere... check the steering column by by the brake pedals... OR if all else fails disconnect the battery....
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Biaggi
92 Red NSX #483
94 CBR900RR