Commander 4WD V8-4.7L VIN N (2006)
Seat Belt Buckle Switch: Description and Operation
SEAT BELT SWITCH
The seat belt switch for this model is actually a Hall Effect-type sensor. This sensor consists of a fixed-position, Hall Effect Integrated Circuit (IC) chip
and a small permanent magnet that is integral to the front seat belt buckle. The front seat belt buckle is located on a molded plastic scabbard and secured
along with the seat belt tensioner mechanism by a nut to the inboard side of the front seat cushion frame. The seat belt switch is connected to the vehicle
electrical system through a two-lead pigtail wire and connector (1) on the front seat belt buckle-half, which is connected to a wire harness connector and
take out of the seat wire harness. A radio noise suppression capacitor is connected in parallel with the IC where the two pigtail wire leads connect to the
Many vehicles, including those equipped with the optional Occupant Classification System (OCS) have a seat belt switch in both front seat belt buckles.
Some vehicles without the OCS only the switch in the driver side front seat belt buckle is connected. The seat belt switch cannot be adjusted or repaired
and, if faulty or damaged, the entire front seat belt buckle-half and tensioner unit must be replaced.
The driver side front seat belt switch is a hard wired input to the Electromechanical Instrument Cluster (EMIC), which also controls the seat belt
indicator based upon the status of the driver side seat belt switch input. On vehicles with the Occupant Classification System (OCS) the passenger side
seat belt switch is designed to provide a status signal to the seat belt switch sense input of the Occupant Restraint Controller (ORC) indicating whether
the passenger side front seat belt is fastened. The ORC uses the seat belt switch signal as an additional logic input to determine the status of the
passenger side front seat belt. The ORC then sends electronic messages to the EMIC to control the seat belt indicator based upon the status of the
passenger side seat belt switch input and electronic messages from the Occupant Classification Module (OCM) indicating whether or not the passenger
side front seat is occupied.
A spring-loaded slide with a small window-like opening is integral to the buckle latch mechanism. When a seat belt tip-half 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. 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 seat belt switch receives a supply current from the EMIC (driver side) or the ORC (passenger side), and the EMIC or ORC senses the status of the
front seat belt through its connection to the seat wire harness. The EMIC and ORC also monitor the condition of the seat belt switch circuit and will
illuminate the airbag indicator in the EMIC then store a Diagnostic Trouble Code (DTC) for any fault that is detected in the seat belt switch circuit. For
proper diagnosis of the seat belt switch, a diagnostic scan tool is required.