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 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 metal of the body support structure. These connections allow the ORC to be operational whenever the ignition switch (Keyless Ignition Node/KIN) status 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 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 front frame 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 the seat track position sensors as well as the driver and passenger seat belt switches.

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.

This vehicle is also equipped with the Occupant Classification System (OCS). The ORC communicates with the Occupant Classification Module (OCM) beneath the passenger seat cushion pan over the CAN data bus. The ORC uses inputs from the OCM as an additional logic input for determining the need for Passenger AirBag (PAB) deployment or suppression. The ORC will internally disable the PAB and the passenger seat belt tensioner deployment circuits if the OCM detects that the passenger seat is unoccupied or that it is occupied by a load that is inappropriate for an airbag deployment.

The ORC also provides electronic messages to the IPC over the CAN data bus, which the IPC uses to control an output to the PAB on/off indicator through the PAB on/off indicator driver circuit. 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 controls airbag indicator operation accordingly. The ORC also uses electronic messaging to control the seat belt indicator in the IPC 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 and, based upon the severity of the monitored impact, determines the level of airbag deployment force required for each seating position. When the programmed conditions are met, the ORC sends the proper electrical signals to deploy the dual multistage airbags at the programmed force levels as well as the seat belt tensioners.

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.