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What exactly do you mean by SDS lite? Can you post a picture of this light is flashing?
That symbol is called the SRS light supplemental restraint system. This is the airbag light. Just to clarify you're saying that when you start the car up the light goes from being illuminated to flashing? When you first turn the key on the light is designed to stay on for about six seconds as it does a self test that should go out.
The information that advance gave you is not accurate. There is no relay that controls the slight the SRS ECU or ECM as some people call it is one complete module under the instrument panel and center console area. Anytime the SRS light is on or flashes indicates there's a malfunction in the airbag system. Without having the specific diagnostic codes from the system is hard to say for sure what's going on. If you don't have diagnostic test equipment you will need to visit your local dealer to have them check for codes.You can check for codes using a jumper wire but the method is very difficult to explain how to do and finding the right pins can be tricky. If that something you think you might want to try I can get you further information otherwise it's best to leave the SRS systems to someone that knows how to deal with them so that you don't create a problem with the airbags.
Please do not forget to rate the assistance that I provided you at three or higher. Once you visit the dealer let me know if you need any other input on what is wrong with the system.