Seat Occupant Sensor: Description and Operation

OCCUPANT CLASSIFICATION SENSOR

CAUTION:
- It is necessary to rezero the OCS system when a front passenger seat cushion is disassembled, a new trim cover installed or an OCS service kit is installed. A diagnostic tool is used to trigger the active command to carry out rezeroing of the OCS system.
- Make sure the seat is completely assembled before rezeroing.
- The following precautions must be taken before rezeroing the OCS system:
- Make sure the OCS system components are connected and no faults are present.
- Make sure the OCS system is not at a temperature below 0°C (32°F) or above 45°C (113°F) when initiating the rezeroing process. If the vehicle has been exposed to extreme cold or hot temperatures, the vehicle must be exposed and kept at a temperature within the limits, 0°C to 45°C (32°F to 113°F) for a minimum of 30 minutes.
- Make sure nothing is present on the passenger seat before rezeroing and nothing is placed on the seat during the rezeroing process.
- Make sure a minimum eight-second time period has passed after cycling the ignition switch ON before the rezeroing process.

NOTE:
- For best results in rezeroing, the OCS system should be at or near room temperature, 10°C to 29°C (50°F to 85°F).
- If the first attempt to rezero the OCS system is unsuccessful, a second attempt must be made.
- Occupant classification sensor (OCS) system components (seat cushion foam pad, bladder with pressure sensor and electronic control unit) are calibrated to each other and are serviced as an assembly. The OCS system components are not to be installed separately. If a new OCS system, OCS system component or seat cushion foam pad are needed, a new OCS system service kit (seat cushion foam pad, bladder with pressure sensor and electronic control unit) must be installed as an assembly.
- To identify between a production OCS system and a service OCS system (OCS service kit), inspect the electronic control unit (ECU) electrical connector. A production OCS system allows the disconnection of the ECU electrical connector. A service OCS system (OCS service kit) has the ECU electrical connector glued to the ECU, it cannot and should not be disconnected or altered. An OCS system service kit also has an in-line 18-pin connector between the OCS ECU and the seat wiring harness.
- The heated seat element on the front passenger seat cushion is not serviceable separately. If a new heated seat element is needed on the front passenger seat cushion, a new occupant classification sensor (OCS) service kit and a new heated seat element must be installed.

The seat occupant classification sensor (OCS) system is found only on the front passenger seat. The front passenger seat OCS system is comprised of a silicone gel-filled bladder mounted between the seat cushion foam and pan, a pressure sensor that is mounted to the seat frame and an electronic control unit which is also mounted to the seat frame. Pressure is applied to the OCS system bladder when weight of any occupant or object in the front passenger seat is present. The pressure is then transferred through a tube, is sensed by the OCS system pressure sensor, then electronically communicated to the OCS system electronic control unit (ECU). Based on preprogrammed set points the OCS system ECU will inform the restraints control module (RCM), via a high-speed controller area network (HS-CAN), of the necessary information. The RCM uses this information in determining if the passenger air bag module is to be deployed in the event of a deployable collision. The RCM also uses this information to illuminate/not illuminate the passenger air bag deactivation (PAD) indicator.

When an OCS system fault is present, the air bag warning lamp will illuminate or the air bag warning chime will be activated (if an air bag indicator fault is present). The SRS then defaults the passenger air bag module to ON (activated) regardless of the size of the occupant in the front outboard passenger seat.

The OCS system components (seat cushion foam pad, bladder with pressure sensor and electronic control unit) are calibrated to each other and are serviced as an assembly. OCS system components are not to be installed separately. If installing a new OCS system, OCS system component or seat cushion foam pad, a new OCS system service kit (seat cushion foam pad, bladder with pressure sensor and electronic control unit) must be installed as an assembly.

The OCS system also interprets a variable voltage signal provided by the safety belt tension sensor to identify the presence of a cinched child safety seat in the front outboard passenger seat installed according to manufacturer instructions. The OCS system then communicates with the restraints control module (RCM), automatically deactivating the passenger air bag module.

The OCS system is also used for operation of the passenger Belt Minder. To deactivate or reactivate the passenger Belt Minder feature, refer to Seat Belt Systems or the owner's manual.