ECM Back-Up Power Circuit (Battery)
WARNING: This page is about a different car, the 2003 Lexus RX 300 and 2003 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.
If circuit or components are faulty, a Diagnostic Trouble Code (DTC) should set. Retrieve DTCs and perform appropriate diagnostic test. See appropriate SELF-DIAGNOSTICS article.