Commander 2WD V6-3.7L (2009)
Air Bag Control Module: Description and Operation
Occupant Restraint Controller - Operation
OPERATION
The microprocessor in 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
ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) 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 microprocessor 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 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 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 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 near the center of the instrument
panel structural 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 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 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.
For the driver side front airbag, additional programming and a logic input from the seat track position sensor aid the ORC in determining the force level
with which to deploy the driver airbag. The ORC also monitors inputs from an internal rollover sensor and up to six additional remote side impact
sensors located on the left and right inner B-pillars, C-pillars and, if the vehicle is equipped with an optional third row seat, on the D-pillars to control
deployment of the side curtain airbag units.
The impact sensors within the ORC are electronic accelerometer sensors that provide additional logic inputs to the ORC microprocessor. These sensors
are used to verify the need for a SRS deployment by also 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 microprocessor 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 microprocessor 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 and either side curtain airbag unit.
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 or
communication between other modules and devices that provide features of the SRS. The most reliable, efficient, and accurate means 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.
