DTC B1900/73: Short in Front Pretensioner Squib RH Circuit; DTC B1901/73: Open in Front Pretensioner Squib RH Circuit; DTC B1902/73: Short to GND in Front Pretensioner Squib RH Circuit; DTC B1903/73: Short to B+ in Front Pretensioner Squib RH 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.