The ORC microprocessor continuously monitors all of the supplemental restraint system electrical circuits to deter-
mine 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/CCN over the CAN data bus to turn ON the air-
bag 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
DTC’s, 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 vehicles 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 front seat is unoccupied or that it is occu-
pied by a load that is inappropriate for an airbag deployment. The ORC also provides a control output to the pas-
senger 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 ineffective OCS component
or circuit, then the ORC sets a DTC and controls the airbag indicator operation accordingly.
The ORC receives battery current through two circuits; an ignition switch output (run) circuit and an ignition switch
output (run-start) circuit. The ORC receives ground through a ground circuit of the instrument panel wire harness.
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 compo-
nents 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 mon-
itors 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 airbags, the ORC also monitors inputs from an internal rollover sensor and four additional remote
impact sensors located on the left and right inner B-pillars and C-pillars to control deployment of the side 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 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 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) at the time of the impact.
To diagnose the ORC or the electronic controls and communication related to ORC operation requires the use of a
diagnostic scan tool. Refer to the appropriate diagnostic information.
PM
RESTRAINTS - SERVICE INFORMATION
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