Occupant Classification System

The Occupant Classification System (OCS) automatically suppresses or enables passenger airbag and seat belt tensioner operation based upon whether or not the passenger side front seat is occupied and, if the seat is occupied, classifies the size of the occupant and whether the seat is occupied by a child seat.

The OCS has an Occupant Classification Module (OCM) that monitors inputs from the seat weight bladder pressure sensor under the passenger front seat cushion and from the belt tension sensor on the passenger front seat belt lower anchor. Based upon those inputs the microprocessor within the OCM classifies the occupant of the passenger front seat. The OCM then sends electronic occupant classification messages to the ORC. The microprocessor and programming of the ORC uses these occupant classification messages to determine whether to enable or disable the deployment circuits for the passenger airbag and seat belt tensioner. These components are not replaceable separately from the seat cushion foam. When replaced as an assembly, the complete service kit (seat cushion, bladder, sensor, OCM, and new wiring harness) MUST be used. 

The OCS electrical circuits and components are continuously monitored by the OCM, and the OCM is continuously monitored by the ORC. A passenger airbag ON/OFF indicator is located in the instrument panel center stack area. This indicator receives battery current whenever the ignition switch is in the ON or START positions, and illuminates only when the ORC pulls the indicator control circuit to ground. The indicator illuminates for about seven seconds as a bulb test each time the ignition switch is turned to the ON or START positions. Following the bulb test, the indicator is turned ON or OFF by the ORC based upon the electronic occupant classification messages received from the OCM. This indicator is illuminated whenever the passenger airbag and seat belt tensioner operation has been suppressed, and is turned OFF whenever they are enabled or when the passenger seat is classified as empty.

When the OCM monitors a problem in any of the OCS circuits or components, it stores a fault code or DTC in its memory circuit and sends an electronic message to the ORC. The ORC then sends an electronic message to the EMIC to turn ON the airbag indicator. If for any reason the OCM is unable to classify the occupant it sends an electronic message to the ORC, and the ORC suppresses passenger airbag and seat belt tensioner operation. Proper testing of the OCS components, the Programmable Communications Interface (PCI) data bus, the electronic message inputs to and outputs from the OCM, the EMIC or the ORC, as well as the retrieval or erasure of a DTC's, requires the use of a scan tool. Refer to the appropriate diagnostic information.

In addition to a diagnostic scan tool, certain diagnostic procedures for the SRS may require the use of the SRS Load Tool (8443 or 8443A) along with the appropriate Load Tool Jumpers and Adapters, or the OCS Seat Weight Tool (9077). Refer to the appropriate diagnostic information.