Occupant Restraint Control (Orc)

DESCRIPTION 

Courtesy of CHRYSLER GROUP, LLC

1 - ORC

The Occupant Restraint Control (ORC) module is located in the passenger compartment of the vehicle, where it is secured by three nuts to two studs of a stamped steel adapter bracket and one stud of the mount welded to the top of the floor panel transmission tunnel under the center front seat section or the center floor console, as the vehicle is equipped. Concealed within a hollow in the center of the molded plastic ORC housing is the electronic circuitry of the ORC which includes a microcontroller, an electronic impact sensor, an electronic safing sensor, an integral Electronic Stability Control (ESC) dynamics sensor and a energy storage capacitor. The ORC also includes an internal rollover sensor. A stamped metal cover plate is secured to the bottom of the ORC housing with screws to enclose and protect the internal electronic circuitry and components.

An arrow printed on a label on the top of the ORC housing provides a visual verification of the proper orientation of the unit, and should always be pointed toward the front of the vehicle. The stamped metal cover plate of the ORC has integral flanges with three mounting holes. A molded plastic electrical connector with two receptacles, each containing numerous terminals, exits the right facing side of the ORC housing. These terminals connect the ORC to the vehicle electrical system through dedicated take outs and connectors of both the instrument panel and the body wire harnesses.

A molded plastic protective cover is installed over the ORC to provide additional moisture contamination protection to the unit. Integral latch features on each side of the cover engage slots at the front and rear of the adapter bracket beneath the base of the ORC housing to secure the cover over the ORC. This protective cover must  be reinstalled following any service requiring its removal.

The impact sensor and safing sensor internal to the ORC are calibrated for the specific vehicle, and are only serviced as a unit with the ORC. The ORC cannot be repaired or adjusted and, if damaged or ineffective, it must be replaced.

OPERATION 

The microcontroller within the ORC contains the Supplemental Restraint System (SRS) logic circuits and controls all of the SRS components. The ORC uses On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with the diagnostic scan tool using the Controller Area Network (CAN) data bus. This method of communication is used for control of the airbag indicator in the Instrument Panel Cluster (IPC) and for SRS diagnosis and testing through the 16-way Data Link Connector (DLC) located on the driver side lower edge of the instrument panel.

The ORC microcontroller continuously monitors all of the SRS electrical circuits to determine the system readiness. If the ORC detects a monitored system fault, it sets an active and stored Diagnostic Trouble Code (DTC) and sends electronic messages to the IPC over the CAN data bus to turn ON the airbag indicator. An active fault only remains for the duration of the fault, or in some cases for the duration of the current ignition cycle, while a stored fault causes a DTC to be stored in memory by the ORC. For some DTCs, if a fault does not recur for a number of ignition cycles, the ORC will automatically erase the stored DTC. For other internal faults, the stored DTC is latched forever.

The ORC receives battery current through two circuits; a fused ignition output (RUN) circuit through a fuse in the Power Distribution Center (PDC), and a fused ignition output (RUN/START) circuit through a second fuse in the PDC. The ORC receives ground through a ground circuit and take out of the instrument panel wire harness that is secured by a ground screw to the body sheet metal. These connections allow the ORC to be operational whenever the status of the ignition switch (Keyless Ignition Node/KIN) is START or ON.

The ORC also contains an energy-storage capacitor. When the ignition switch status is START or ON, this capacitor is continually being charged with enough electrical energy to deploy the SRS components 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 ORC during an impact.

Various sensors within the ORC are continuously monitored by the ORC logic. These internal sensors, along with several external impact sensor inputs allow the ORC to determine both the severity of an impact and to verify the necessity for deployment of any SRS components. Two remote front impact sensors are located on the back of the right and left ends of the lower radiator cross member near the front of the vehicle. The electronic impact sensors are accelerometers that sense the rate of vehicle deceleration, which provides verification of the direction and severity of an impact.

The ORC also monitors inputs from up to six additional remote side impact sensors located within both the left and right front doors, the B-pillars and the C-pillars to control deployment of the side curtain airbag units and, if equipped, the seat airbag units. The ORC also monitors an internal rollover sensor for inflation of the Side AirBag Inflatable Curtains (SABIC).

The impact sensors within the ORC are electronic accelerometer sensors that provide additional logic inputs to the ORC microcontroller. These sensors are used to verify the need for a SRS component deployment by detecting impact energy of a lesser magnitude than that of the primary electronic impact sensors, and must exceed a safing threshold in order for the SRS components to deploy. A separate impact sensor within the ORC provides confirmation to the ORC microcontroller of side impact forces. This separate sensor is a bi-directional unit that detects impact forces from either side of the vehicle.

Pre-programmed decision algorithms in the ORC microcontroller determine when the deceleration rate as signaled by the impact sensors indicate an impact that is severe enough to require SRS protection and, based upon 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 ORC sends the proper electrical signals to deploy the dual multistage front airbags at the programmed force levels, the front seat belt tensioners, side curtain and seat airbag.

The ORC also contains an integral Electronic Stability Control (ESC) dynamics sensor. The ORC microcontroller energizes the ESC dynamics sensor, then relays the sensor outputs to the Antilock Brake System (ABS) Module over the CAN data bus. Refer to MODULE, ANTI-LOCK BRAKE SYSTEM (ABS), DESCRIPTION AND OPERATION .

For specific inputs and outputs of the ORC. Refer to RESTRAINTS, DESCRIPTION AND OPERATION .