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: Wiring Diagram
WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.