WARNING: This page is about a different car, the 2004 Lexus SC 430, 2003 Lexus SC 430, and 2002 Lexus SC 430. However, it is still accessible from the selected car via links, so may be relevant.
For wiring diagram see Figure. For testing procedure see Fig 1 and Fig 2
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Fig 1: Testing Procedure Malfunction In ECU (VSC Warning Light - 1 Of 2)