Nitro 2WD V6-4.0L (2007)
Air Bag Control Module: Description and Operation
Operation
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) (also known as the Cab Compartment Node/CCN) 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 vehicles so equipped, the ORC provides voltage to the seat track position sensors on the inboard passenger and driver side front seat upper seat
tracks. The ORC then monitors return inputs from each of the sensors on dedicated hard wired data communication circuits. The seat track position
sensors provide additional logic inputs to the ORC microprocessor that allow it to determine the position of the front seat passenger and the driver
relative to the front airbags for determining the force level with which to deploy the multistage front airbags.
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
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 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; a fused ignition switch output (run) circuit through a fuse in the Totally Integrated Power Module
(TIPM), and a fused ignition switch output (run-start) circuit through a second fuse in the TIPM. The ORC receives ground through a ground circuit and
take out 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. Refer to the appropriate wiring information for additional details.
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 ends of the front end module 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 and four additional remote impact sensors located on the left and right inner B
and C-pillars 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. A second safing sensor within the ORC provides
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 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. For vehicles equipped with the OCS, the passenger front airbag and seat belt tensioners 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.
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 supplemental restraint system. 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.
