Description And Operation: 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 Occupant Classification Module (OCM) (6) 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 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 bolted to the outboard upper seat track.
- Pressure Hose - Beneath the seat cushion a length of clear poly hose serves as the OCS pressure hose (5). The hose is securely clamped at one end to a hose nipple fitting that extends downward from the seat weight sensor, 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 seat weight sensor.
- Seat Cushion Foam - The passenger front seat cushion foam (1) is an integral part of the factory-calibrated OCS.
- Seat Weight Sensor
- The seat weight sensor is sandwiched between the seat cushion springs and the seat cushion foam. A heavy plastic insulator pad (4) is installed between the lower surface of the bladder and the seat cushion pan and springs. The bladder and pad are secured near the forward end to the seat cushion pan by three 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.
- Heat Mat - If equipped with heated seats, the heat mat is sandwiched between the seat trim and the seat cushion foam and adhered to the foam. This component will be included in the service kits for heated seats and vented seats.
- Vent Bag - If equipped with vented seats, the vent bag is sandwiched between the seat foam and the Occupant Classification Module and adhered to the foam. This component will be included in the service kit for vented seats.
All of the components that make up the OCS, including the heat mat and vent bag, are a factory-calibrated and assembled unit. If the vehicle is equipped with either the heated seat, vented seat or both, these components must be replaced with the rest of the OCS components as they are calibrated together as one unit at the factory. The OCS components cannot be adjusted or repaired and, if damaged or ineffective, they must all be replaced as a calibrated unit.
Any time the OCM is removed or replaced for any reason, the new OCS data must be configured within the Occupant Restraint Controller (ORC) using a diagnostic scan tool. Refer to the appropriate diagnostic information.