DTC B1815/54: Short in Front Passenger Side Squib 2nd Step Circuit; DTC B1816/54: Open in Front Passenger Side Squib 2nd Step Circuit; DTC B1817/54: Short to GND in Front Passenger Side Squib 2nd Step Circuit; DTC B1818/54: Short to B+ in Front Passenger Side Squib 2nd Step Circuit [08/2013 - ]: Wiring Diagram
WARNING: This page is about a different car, the 2014 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.