July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!
SIR Schematics
WARNING: This page is about a different car, the 2010 Cadillac SRX. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Power, Ground, Serial Data & Passenger Presence System Circuit Schematic
Courtesy of GENERAL MOTORS CORP.
Fig 2: Front Impact Sensors & Seat Belt Pretensioners Circuit Schematic