DTC B1810/53: Short in Driver Side Squib 2nd Step Circuit; DTC B1811/53: Open in Driver Side Squib 2nd Step Circuit; DTC B1812/53: Short to GND in Driver Side Squib 2nd Step Circuit; DTC B1813/53: Short to B+ in Driver 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.