Switch, Seat Belt: Operation
The driver front seat belt switch is designed to control a hardwired sense input to the Occupant Restraint Controller (ORC), while the passenger front seat belt switch controls a similar input to the Occupant Classification Module (OCM). A spring-loaded slide with a small window-like opening is integral to each buckle latch mechanism. When a seat belt tip is inserted and latched into the seat belt buckle, the slide is pushed downward and the window of the slide exposes the Hall Effect Integrated Circuit (IC) chip within the buckle. The field of the permanent magnet induces a current within the chip. The chip provides this induced current as an output to the ORC or the OCM. When the seat belt is unbuckled, the spring-loaded slide moves upward and shields the IC from the field of the permanent magnet, causing the output current from the seat belt switch to be reduced. The front seat belt switches receive a supply of current from the ORC or the OCM, and the ORC or OCM senses the status of the front seat belt switch through its connection to the seat wire harnesses.
In vehicles built for certain export markets equipped with rear seat belt switches, the seat belt switches are designed to control a path to ground for the seat belt switch sense inputs of the ORC. When the rear seat belt tip is inserted into the seat belt buckle, the switch closes the path to ground; and, when the rear seat belt tip is removed from the seat belt buckle, the switch opens the ground path. The switch is actuated by the latch mechanism within the seat belt buckle. The seat belt switch is connected in series between ground and the seat belt switch sense input of the ORC. The seat belt switch receives ground at all times through its pigtail wire connection to the seat wire harness from a take out of the body wire harness. An eyelet terminal connector on the body wire harness ground take out is secured to the body sheet metal.
The ORC or the OCM provides electronic seat belt switch status messages to the Instrument Panel Cluster (IPC) over the Controller Area Network (CAN) data bus. The IPC uses these messages as an additional logic input for control of the seat belt indicator. In vehicles built for certain export markets equipped with rear seat belt switches, the IPC reads the messages received from the ORC then controls the Seat Belt Reminder (SBR) indications in the overhead console using Local Interface Network (LIN) data bus communication. The ORC and OCM monitor the condition of the seat belt switch circuits and will store a Diagnostic Trouble Code (DTC) for any fault that is detected.
The hardwired circuits between the seat belt switches and the ORC or OCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the switches or the electronic controls and communication between other modules and devices that provide some features of the seat belt reminder system. The most reliable, efficient and accurate means to diagnose the seat belt switches or the electronic controls and communication related to seat belt switch operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.