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Dodge Dakota (ND). Manual - part 462

airbag on/off indicator in the instrument panel based upon the electronic occupant classification messages it
receives from the OCM.

The OCM also sends electronic driver and passenger seat track position messages to the ORC over the CAN data
bus. The ORC uses the seat track position data as an additional logic input for determining the force level with
which to deploy the multistage front airbags.

The OCM microprocessor continuously monitors all of the OCS electrical circuits and components to determine the
system readiness. If the OCM detects a monitored system fault, it sets an active and stored Diagnostic Trouble
Code (DTC) and sends the appropriate electronic messages to the ORC over the CAN data bus. Then the ORC
sets a DTC and sends messages to control the airbag indicator operation accordingly. 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 OCM and the ORC. For some DTCs, if a fault does not recur for a
number of ignition cycles, the OCM will automatically erase the stored DTC. For other internal faults, the stored
DTC is latched forever.

The OCM receives battery current on a fused ignition switch output (run-start) circuit through a fuse in the Junction
Block (JB). The OCM receives ground through a ground circuit and take out of the body wire harness. These con-
nections allow the OCM to be operational whenever the ignition switch is in the Start or On positions.

The hard wired inputs and outputs for the OCM may be diagnosed and tested using conventional diagnostic tools
and procedures. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the OCM,
the CAN data bus, or the electronic message inputs to and outputs from the OCM. The most reliable, efficient, and
accurate means to diagnose the OCM, the CAN data bus network, and the electronic message inputs to and out-
puts from the OCM requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.

REMOVAL

WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental
restraint system before attempting any steering wheel, steering column, airbag, occupant classification sys-
tem, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect
and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge
before performing further diagnosis or service. This is the only sure way to disable the supplemental
restraint system. Failure to take the proper precautions could result in accidental airbag deployment.

NOTE: A non-calibrated Occupant Classification Module (OCM) is available for separate service replace-
ment. The OCM and all of the other components of the Occupant Classification System (OCS) including the
passenger side front seat, the seat weight sensors, the passenger or driver seat track position sensor and
the seat adjusters, cushion, back, frame, foam, springs, and wiring harness are a factory-calibrated and
assembled unit. Any time any one of these components is removed or replaced for any reason, the OCM
must be re-calibrated using a diagnostic scan tool, the Occupant Classification Seat Weight special tool,
and the Occupant Classification System Verification Test. Refer to the appropriate diagnostic procedures.

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RESTRAINTS - SERVICE INFORMATION

1. Disconnect and isolate the battery negative cable.

Wait two minutes for the system capacitor to dis-
charge before further service.

2. Reach under the front edge of the passenger side

front seat cushion to access and disconnect the
body wire harness and seat wire harness connec-
tors

from

the

Occupant

Classification

Module

(OCM) connector receptacles (4) located on the
forward facing end of the module.

3. Remove the two screws (2) that secure the OCM

to the OCM bracket (1) on the underside of the
passenger side front seat cushion frame.

4. Remove the OCM (3) from under the passenger

side front seat.

INSTALLATION

1. Carefully position the Occupant Classification Mod-

ule (OCM) (3) to the OCM bracket (1) on the
underside of the passenger side front seat cushion
frame. When the OCM is correctly positioned, the
connector receptacles on the module will be
pointed forward in the vehicle.

2. Install and tighten the two screws (2) that secure

the OCM to the OCM bracket. Tighten the screws
to 2 N·m (15 in. lbs.).

3. Reconnect the body wire harness and seat wire

harness connectors to the OCM connector recepta-
cles (4) located on the forward facing end of the
module. Be certain that the latches and locks on
both connectors are each fully engaged.

4. Do not reconnect the battery negative cable at this

time. The supplemental restraint system verification
test procedure should be performed following ser-
vice of any supplemental restraint system compo-
nent. (Refer to 8 - ELECTRICAL/RESTRAINTS -
STANDARD PROCEDURE - VERIFICATION TEST).

RESTRAINTS - SERVICE INFORMATION

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5. Following successful completion of the supplemental restraint system verification test procedure, perform the

Occupant Classification System Verification Test using a diagnostic scan tool. Refer to the appropriate diagnostic
procedures.

MODULE-OCCUPANT RESTRAINT CONTROLLER

DESCRIPTION

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 instru-
ment 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 sen-
sor, an electronic safing sensor, and an energy stor-
age 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 ori-
entation 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 ser-
viced 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. (Refer
to 8 - ELECTRICAL/INSTRUMENT CLUSTER/AIRBAG INDICATOR - OPERATION).

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 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

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RESTRAINTS - SERVICE INFORMATION

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 sta-
tus 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 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 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, effi-
cient, 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.

REMOVAL

RESTRAINTS - SERVICE INFORMATION

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