Module, Occupant Classification: Description
In vehicles manufactured for domestic markets, the passenger side front seat incorporates the Occupant Classification System (OCS). The OCS consists of a single factory-calibrated unit, which includes the following components:
- Electronic Pressure Sensor - The electronic pressure sensor is integral and internal to the Occupant Classification Module (OCM). Only the hose nipple for the pressure hose is visible on the outside of the OCM housing. The remainder of the sensor and the sensor circuitry are concealed and protected within the molded black plastic OCM housing.
- Occupant Classification Module
- The OCM (3) is located beneath the front of the passenger front seat cushion. Concealed within a hollow in the center of the molded black plastic OCM housing is the electronic circuitry of the module. The module housing is sealed to enclose and protect the internal electronic circuitry. A connector receptacle integral to the front of the OCM housing contains terminal pins that connect the sensor to the vehicle electrical system through a dedicated take out and connector of the passenger front seat wire harness. A hose nipple formation is integral to the OCM housing.
A slot integral to the top of the OCM housing snaps over a blade on a stamped metal bracket riveted to the inboard upper seat track.
- Pressure Hose - Beneath the seat cushion a length of clear poly hose serves as the OCS pressure hose (4). The hose is securely clamped at one end to a hose nipple fitting that extends downward from the Seat Weight Sensor (SWS), and at the opposite end to the hose nipple formation of the electronic pressure sensor integral to the outside of the OCM housing. The pressure sensor circuitry is internal and integral to the OCM. The pressure hose is filled with the same silicone fluid that fills the SWS.
- Seat Cushion Foam - There are unique cushion foams for each passenger seat trim type and for vehicles equipped with optional heated or heated and ventilated front seats. The passenger front seat cushion foam (1) is an integral part of the factory-calibrated OCS. The proper foam and a calibrated OCM are both included in the service kit and, if the vehicle is so equipped, the seat cushion heat or heat and ventilation units.
- Seat Weight Sensor
- The Seat Weight Sensor (SWS) is sandwiched between the seat cushion springs and the seat cushion foam. A heavy jute-like insulator pad (2) is installed between the lower surface of the bladder (5) and the seat cushion pan and springs. The bladder and pad are secured near the forward end to the seat cushion pan by two plastic push-in fasteners.
The bladder consists of two sheets of an elastomeric material and a molded plastic hose nipple fitting. The two sheets of elastomeric material are sealed together around their perimeter and joined at numerous specific intervals within their field. The hose nipple fitting is sealed to a small round hole in the lower surface of the bladder and is pointed downward where it passes through a clearance hole in the insulator pad and extends to just below the seat cushion springs. The bladder is filled with a silicone fluid to become a pliable, quilted, resistive mat and is connected to a pressure hose that connects it to the electronic pressure sensor within the OCM unit.
All of the components that make up the OCS are a factory-calibrated and assembled unit. The OCS components cannot be adjusted or repaired and, if damaged or ineffective, they MUST BE REPLACED AS A CALIBRATED UNIT. Any time the OCS and or the seat foam, is removed or replaced for any reason, the new OCS data must be re-zeroed using a diagnostic scan tool. Refer to the appropriate diagnostic information.