Circuit/System Description
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
The seat belt buckle switch is located within the seat belt buckle assembly and provides an input to the inflatable restraint sensing and diagnostic module (SDM). The SDM supplies a low reference circuit and a seat belt switch signal circuit to determine a buckled or unbuckled condition.
If the SDM determines the driver seat belt has not been buckled, the SDM will send a serial data message to the instrument panel clutch (IPC) to illuminate the seat belt warning indicator. If the SDM determines that a passenger is sitting in the passenger seat and the seat belt has not been buckled, the SDM will send a serial data message to the passenger presence system (PPS) display to illuminate the passenger seat belt warning indicator.