Occupant Restraint Controller: Operation

The microprocessor in the Occupant Restraint Controller (ORC) contains the Supplemental Restraint System (SRS) logic circuits and controls all of the SRS components. The Occupant Restraint Controller (ORC) uses On-Board Diagnostics (OBD) and Controller Area Network (CAN) to communicate with other electronic modules in the vehicle as well as with the DRBIII(R) scan tool.

The Occupant Restraint Controller (ORC) microprocessor continuously monitors all of the Supplemental Restraint System (SRS) electrical circuits to determine the system status. If the Occupant Restraint Controller (ORC) detects a monitored system fault, it sets an active and a stored Diagnostic Trouble Code (DTC). A message is sent to the Instrument Cluster (IC) over the Controller Area Network (CAN) data bus to illuminate the airbag warning indicator lamp.

The Occupant Restraint Controller (ORC) also monitors the seat belt switch which is located internal to each of the front seat belt buckles to determine whether the seat belts are fastened properly. If the seat belt is not fastened a signal is sent to the Instrument Cluster (IC) over the Controller Area Network (CAN) data bus to illuminate the seatbelt indicator lamp.

The Occupant Restraint Controller (ORC) receives battery current through two circuits; a fused ignition switch output (RUN) circuit through a fuse in the underhood accessory fuse block, and a fused ignition switch output (START-RUN) circuit through a second fuse in the underhood accessory fuse block. The Occupant Restraint Controller (ORC) is grounded through a ground circuit of the instrument panel floor wire harness. This has a single eyelet terminal connector secured by the bolt to the Occupant Restraint Controller (ORC) mount on the floor panel of the transmission tunnel. These connections allow the Occupant Restraint Controller (ORC) to be operational whenever the ignition switch is in the Start or On positions.

The Occupant Restraint Controller (ORC) also contains a capacitor. When the ignition switch is in the Start or On positions, this capacitor is continually being charged with enough voltage to deploy the airbags for up to one second following a battery disconnect or failure. The purpose of the capacitor is to provide backup SRS protection in case there is a loss of battery current supply to the Occupant Restraint Controller (ORC) during an impact.

Two sensors are contained within the Occupant Restraint Controller (ORC), an electronic impact sensor and a safing sensor. The Occupant Restraint Controller (ORC) also monitors inputs from two remote side impact sensors located under the carpet directly below the front seats, to control the deployment of the side impact airbag units.

The safing sensor is an electronic accelerometer sensor within the Occupant Restraint Controller (ORC) that provides an additional logic input to the Occupant Restraint Controller (ORC) microprocessor. The safing sensor is used to verify the need for a Supplemental Restraint System (SRS) deployment by detecting the impact energy of a collision. The impact energy must exceed the safing threshold in order for the airbags to deploy.

Pre-programmed decision algorithms in the Occupant Restraint Controller (ORC) microprocessor determine when the deceleration rate indicates an impact that is severe enough to require supplemental restraint system protection. Based upon the status of the seat belt switch inputs and the severity of the monitored impact, determines the level of front airbag deployment force required for each front seating position. When the programmed conditions are met, the Occupant Restraint Controller (ORC) sends the proper electrical signals to deploy the front airbags and the Seat Belt Tensioner's (SBT) at the programmed force levels.

The Occupant Restraint Controller (ORC) determines the level of front air bag deployment force for each seating position based on the seat belt switch input status and the severity of the impact. When the predetermined impact conditions are met the Occupant Restraint Controller (ORC) deploys the front airbags and activates the Seat Belt Tensioner's (SBT).