Module-Occupant Restraint Controller
MODULE-OCCUPANT RESTRAINT CONTROLLERDESCRIPTION
The Occupant Restraint Controller (ORC) (1) is located below the instrument panel center stack in the passenger compartment of the vehicle, where it is secured by three nuts to three studs on a stamped steel mounting bracket welded onto the top of the floor panel transmission tunnel just forward of the instrument panel center support bracket. Concealed within a hollow in the center of the die cast aluminum ORC housing is the electronic circuitry of the ORC which includes a microprocessor, an electronic impact sensor, an electronic safing sensor, and an energy storage capacitor. 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 (2) 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 ORC housing has
three integral flanges with mounting holes. Two are on the corners oriented towards the rear of the vehicle, and one is near the center of the side facing the front of the vehicle. A molded plastic electrical connector (3) with two receptacles, each containing up to thirty-two terminal pins, exits the left facing side of the ORC housing. These terminal pins connect the ORC to the vehicle electrical system through two dedicated take outs and connectors, one each from the instrument panel and the body wire harnesses.
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. In addition, there are unique versions of the ORC for vehicles with or without the optional side curtain airbags. The ORC cannot be repaired or adjusted and, if damaged or faulty, it must be replaced.
OPERATION
The microprocessor in the Occupant Restraint Controller (ORC) contains the supplemental restraint system logic circuits and controls all of the supplemental restraint system 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 ElectroMechanical Instrument Cluster (EMIC) and for supplemental restraint system diagnosis and testing through the 16-way data link connector located on the driver side lower edge of the instrument panel.
The ORC microprocessor continuously monitors all of the supplemental restraint system 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 EMIC 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 switch 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.
On models equipped with the Occupant Classification System (OCS), the ORC communicates with the Occupant Classification Module (OCM) over the CAN data bus. The ORC will internally disable the passenger airbag and seat belt tensioner deployment circuits if the OCM detects that the passenger side front seat is unoccupied or that it is occupied by a load that is inappropriate for an airbag deployment. The ORC also provides a control output to the passenger airbag on/off indicator through the passenger airbag 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 faulty OCS component or circuit, then the ORC sets a DTC and controls the airbag indicator operation accordingly.
In club cab models, the ORC also monitors a resistor multiplexed input from the passenger airbag on/off switch. If the passenger airbag on/off switch is set to the Off position, the ORC turns on the passenger airbag on/off indicator and will internally disable the passenger airbag and seat belt tensioner from being deployed, regardless of the status of the input from the OCS.
The ORC receives battery current through two circuits; a fused ignition switch output (run) circuit through a fuse in the Junction Block (JB), and a fused ignition switch output (run-start) circuit through a second fuse in the JB. The ORC receives ground through a ground circuit and take out of the instrument panel wire harness. This take out has a single eyelet terminal connector that is secured by a ground screw to the left side of the floor panel transmission tunnel near the center of the instrument panel center support. These connections allow the ORC to be operational whenever the ignition switch is in the Start or On positions.
The ORC also contains an energy-storage capacitor. When the ignition switch is in the Start or On positions, this capacitor is continually being charged with enough electrical energy to deploy the supplemental restraint components for up to one second following a battery disconnect or failure. The purpose of the capacitor is to provide backup supplemental restraint system protection in case there is a loss of battery current supply to the ORC during an impact.
Two sensors are contained within the ORC, an electronic impact sensor and a safing sensor. The ORC also monitors inputs from two remote front impact sensors located on the back of the right and left vertical members of the radiator support 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. On vehicles equipped with optional side curtain airbags the ORC also monitors inputs from two additional remote impact sensors located on the floor panel just behind the front seat crossmember beneath the outboard side of the left and right front seats to control deployment of the side curtain airbag units.
The safing sensor is an electronic accelerometer sensor within the ORC that provides an additional logic input to the ORC microprocessor. The safing sensor is used to verify the need for a supplemental restraint 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 airbags to deploy. Vehicles equipped with optional side curtain airbags, feature a second safing sensor within the ORC to provide confirmation to the ORC microprocessor of side impact forces. This second safing sensor is a bi-directional unit that detects impact forces from either side of the vehicle.
Pre-programmed decision algorithms in the ORC microprocessor determine when the deceleration rate as signaled by the impact sensors and the safing sensors indicate an impact that is severe enough to require supplemental restraint system protection and, based upon the severity of the monitored impact, determines the level of front air-bag 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 and, if the vehicle is so equipped, either side curtain airbag unit. For vehicles equipped with the OCS, the passenger front airbag and seat belt tensioner will be deployed by the ORC only if enabled by the OCM messages (passenger airbag on/off indicator Off) and, on club cab models, the passenger airbag on/off switch at the time of the impact.
The hard wired inputs and outputs for the ORC may be diagnosed and tested using conventional diagnostic tools and procedures. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the ORC, the CAN data bus network, or the electronic message inputs to and outputs from the ORC. The most reliable, efficient, and accurate means to diagnose the ORC, the CAN data bus, and the electronic message inputs to and outputs from the ORC requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.