Dodge ZB 2005 Service Manual page 346

ZB
OCCUPANT RESTRAINT CONTROLLER (Continued)
of the ORC housing with four screws to enclose and
protect the internal electronic circuitry and compo-
nents. This is not to be removed for any reason and
service to the ORC is not to be attempted.
An arrow printed on the 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. Two molded
plastic electrical connector receptacles exit the for-
ward side of the ORC housing. These two receptacles
connect the ORC to the vehicle electrical system.
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. The ORC
cannot be repaired or adjusted and, if damaged or
faulty, must be replaced.
OPERATION
The microprocessor in the Occupant Restraint Con-
troller (ORC) contains the supplemental restraint
system logic circuits and controls all of the supple-
mental 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 DRBIII scan tool using the Programma-
ble Communications Interface (PCI) data bus net-
work. This method of communication is used for
control of the airbag indicator in the ElectroMechani-
cal 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 cir-
cuits 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 PCI data
bus to turn on the airbag indicator. An active fault
only remains for the duration of the fault or in some
cases 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 for-
ever.
The ORC also monitors a Hall effect-type seat belt
switch located in the buckle of each front seat belt to
determine whether the seat belts are buckled, and
provides an input to the EMIC over the PCI data bus
to control the seat belt indicator operation based
upon the status of the driver side front seat belt
switch.
The ORC receives battery current through two cir-
cuits; a fused ignition switch output (RUN) circuit
through a fuse in the Power Distribution Center
(PDC), and a fused ignition switch output (START/
RUN) circuit through a second fuse in the PDC. The
ORC is grounded through a ground circuit and take
out of the instrument panel floor wire harness. These
connections allow the ORC to be operational when-
ever the ignition switch is in the START or ON posi-
tions.
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 airbags
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
electronic impact sensors are accelerometers that
sense the rate of vehicle deceleration, which provide
verification of the direction and severity of an
impact. The safing sensor is an electronic accelerom-
eter sensor within the ORC that provides an addi-
tional logic input to the ORC microprocessor. The
safing sensor is used to verify the need for a supple-
mental restraint deployment by detecting impact
energy of a lesser magnitude than that of the pri-
mary electronic impact sensors, and must exceed a
safing threshold in order for the airbags to deploy.
Pre-programmed decision algorithms in the ORC
microprocessor determine when the deceleration rate
as signaled by the impact sensor and the safing sen-
sors indicate an impact that is severe enough to
require supplemental restraint system protection
and, based upon the status of the seat belt switch
inputs and 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 multi-
stage front airbags at the programmed force levels.
To properly diagnose the ORC, a DRBIII scan tool
and the appropriate Body Diagnostic Procedures
manual must be used.
REMOVAL
(1) Open deck lid.
(2) Remove four bolts to battery compartment
cover and remove cover.
(3) Disconnect and isolate the battery negative
cable.
(4) Wait two minutes for the airbag system reserve
capacitor to discharge before beginning any airbag
system or instrument panel component service.
(5) Remove six allen screws to shifter bezel.
RESTRAINTS 8O - 7