Seat Belt Switch: Operation

The seat belt switch is designed to provide a status signal to the seat belt switch sense input of the Airbag Control Module (ACM) indicating whether the driver side front seat belt is fastened. The ACM sends electronic messages to the ElectroMechanical Instrument Cluster (EMIC) to control the seat belt indicator based upon the status of the driver side front seat belt switch.

A spring-loaded plastic slide with a small, enclosed permanent magnet 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 into close proximity of 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 ACM, which monitors the current to determine the status of the driver side front seat belt. When the seat belt is unbuckled, the spring-loaded slide and permanent magnet move upward and away from the IC, causing the output current from the seat belt switch to be reduced.

The seat belt switch receives a supply of current from the ACM, and the ACM senses the status of the driver side front seat belt through its pigtail wire connection to the seat wire harness. The ACM also monitors 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. Refer to the appropriate diagnostic information.