Occupant Classification System

Vehicles manufactured for the North American market are equipped with the Occupant Classification System (OCS). The 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 side front seat cushion and from the belt tension sensor on the passenger side front seat belt lower anchor. Based upon those inputs the microprocessor within the OCM classifies the occupant of the passenger side front seat. The OCM then sends electronic occupant classification messages to the Airbag Control Module (ACM). The microprocessor and programming of the ACM determines whether to enable or disable the deployment circuits for the passenger airbag and seat belt tensioner; and, if enabled, what force level should be used to deploy each front airbag.

The OCS electrical circuits and components are continuously monitored by the OCM, and the OCM is continuously monitored by the ACM. A passenger airbag on/off indicator is located in the inboard end cap of the instrument panel grab handle. This indicator receives battery current whenever the ignition switch is in the On or Start positions, and illuminates only when the ACM 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 ACM 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 the seat is empty or when the seat is occupied and the passenger airbag and seat belt tensioner are enabled.

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 ACM. The ACM 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 ACM, and the ACM 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 ACM, as well as the retrieval or erasure of a DTC from the OCM, the ACM or the EMIC requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

See the owner's manual in the vehicle glove box for more information on the features, use and operation of the OCS.