Possible Causes
WARNING: This page is about a different car, the 2004 Lexus ES 330. However, it is still accessible from the selected car via links, so may be relevant.
Diagnostic Trouble Code (DTC) 23/B1630 could be caused by short to ground, short to battery or open in left rear air bag sensor wiring harness, left rear air bag sensor malfunction or air bag sensor assembly malfunction.