Security Indicator Light Circuit: Description
WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.
Even when the theft deterrent system is in the disarmed state, the security indicator blinks due to a signal output from the immobilizer system. The security indicator blinks continuously due to a continuous signal received from the immobilizer system while in the armed state
The main body ECU RH (cowl side junction block RH) causes the security indicator to light up or blink only during the arming preparation state and alarm sounding state.