Module, Occupant Restraint Controller: Operation: Operation

The microcontroller within the Occupant Restraint Controller (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 and seat belt indicators in the Instrument Cluster (IC) (also known as the Instrument Panel Cluster/IPC) and for SRS diagnosis and testing through the 16-way data link connector 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 IC 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. In the case of some faults which have not recurred 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 (also known as the Keyless Ignition Node/KIN or the IGnition Node Module/IGNM) 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 event.

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 sides of the Front End Module (FEM) carrier inboard of the headlamps 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 an internal rollover sensor, the seat track position sensors, the front seat belt switches, the rear seat belt switches (export markets only) and six additional remote side impact sensors located on the left and right front door hardware module carriers, on the right and left lower B-pillars and on the right and left lower C-pillars to control deployment of the side curtain airbag units, the front seat airbags (also known as pelvic and thoracic airbags) and, if equipped, the rear seat airbags. The ORC also uses electronic message inputs from the Occupant Classification Module (OCM) beneath the passenger front seat cushion pan and will send electronic messages to the IC to illuminate the seat belt indicator when appropriate.

The impact sensors within the ORC are electronic accelerometer sensors that provide an additional logic input 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. The ORC uses this input to verify the need for side curtain airbags or seat airbag deployment. This separate sensor is a bi-directional unit that detects impact forces from either side of the vehicle.

In most domestic markets this vehicle is also equipped with the Occupant Classification System (OCS). The ORC communicates with the Occupant Classification Module (OCM) over the CAN data bus. The ORC uses inputs from the OCM as an additional logic input for determining the appropriate level of airbag deployment force required for the front passenger seating position. The OCM notifies the ORC when it has detected a monitored system fault and stored a DTC in its memory for any ineffective OCS component or circuit, then the ORC sets a DTC and will send electronic messages to the IC to illuminate the airbag indicator as appropriate.

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. Based upon the severity of the monitored impact as well as the seat track position sensor and the passenger front seat OCS inputs, the ORC logic 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 knee airbags, the front seat belt tensioners, either side curtain airbag and either right or left, front and rear seat airbag units.

The ORC also contains a integral Electronic Stability Control (ESC) dynamics sensor (also known as the yaw sensor or the sensor cluster). The ORC microcontroller energizes the ESC dynamics sensor, then relays the sensor outputs to the Antilock Brake Module (ABM) over the CAN data bus. Refer to MODULE, ANTI-LOCK BRAKE SYSTEM, OPERATION .

The Body Control Module (BCM) stores and compares vehicle configuration data with the ORC as well as with other Electronic Control Units (ECU) in the vehicle. This process is referred to as PRogramming Of Configuration of Systems Integrated (PROCSI) (also known as PROXI). If a configuration mismatch is detected, the BCM sets a DTC. A configuration mismatch DTC will require the performance of a Restore BCM PROXI Configuration routine, or a PROXI Configuration Alignment routine using a diagnostic scan tool.

The hard wired inputs and outputs for the ORC may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the ORC or the electronic controls and communication between other modules and devices that provide some features of the SRS. The most reliable, efficient and accurate means to diagnose the ORC or the electronic controls and communication related to SRS operation requires the use of a diagnostic scan tool and may also require the use of the SRS Load Tool special tool along with the appropriate Load Tool Jumpers and Adapters. Refer to the appropriate diagnostic information.