Chrysler Pacifica. Manual — part 534

(3) Install the two retaining screws to the impact

sensor (Fig. 33). Torque screws to 7.3 N·m (65 in.
lbs.).

(4) Install the quarter trim panel for the side of

the vehicle that you are replacing the side impact
sensor (Refer to 23 - BODY/INTERIOR/QUARTER
TRIM PANEL - INSTALLATION).

WARNING: DO NOT CONNECT THE BATTERY NEG-
ATIVE

CABLE.

(Refer

to

8

-

ELECTRICAL/RE-

STRAINTS - DIAGNOSIS AND TESTING - AIRBAG
SYSTEM)

FIRST.

FAILURE

TO

DO

SO

COULD

RESULT IN OCCUPANT PERSONAL INJURY OR
DEATH.

(5) Verify vehicle and system operation.
(6) Close hood.

OCCUPANT CLASSIFICATION
MODULE

DESCRIPTION

The Occupant Classification Module (OCM) (Fig.

34) is secured with two screws to a stamped steel
mounting bracket welded onto the underside of the
passenger front seat cushion frame near the inboard
front corner (Fig. 35). Concealed within a hollow in
the center of the molded plastic OCM housing is a
microprocessor and the other electronic circuitry of
the module. The module housing is sealed to enclose

and protect the internal electronic circuitry. The
OCM software is flash programmable.

A non-calibrated OCM is the only component of the

Occupant Classification System (OCS) that is avail-
able for separate service replacement. The OCS com-
ponents of the passenger side front seat cushion
including the cushion frame, insulator pad, seat
weight bladder and pressure sensor, seat cushion
foam, wiring harness and the OCM are a factory-cal-
ibrated and assembled unit. Once this unit is con-
nected

to

a

vehicle

electrically,

the

calibration

settings are uploaded from the calibrated OCM and
stored in the memory of the Occupant Restraint Con-
troller (ORC). If only the OCM is subsequently
replaced, the new, non-calibrated OCM learns the
proper calibration settings from the ORC after it is
connected to the vehicle electrically.

The OCM cannot be adjusted or repaired and, if

damaged or faulty, it must be replaced. The compo-
nents of the passenger front seat cushion are ser-
viced only as a factory-calibrated, assembled and
tamper-evident unit. Only the OCM and the seat
cushion trim are available for separate service
replacement. Once a service replacement package has
been installed in a vehicle, the OCM can thereafter
be serviced only by replacing the entire passenger

Fig. 34 OCCUPANT CLASSIFICATION MODULE

(OCM) - TYPICAL

1 - OCCUPANT CLASSIFICATION MODULE
2 - CONNECTOR LOCK TOWER
3 - CONNECTOR RECEPTACLE
4 - MOUNTING TAB (2)

Fig. 35 OCM LOCATION

1 - OCCUPANT CLASSIFICATION MODULE (OCM)
2 - LOCK TOWER
3 - LOCK PIN
4 - CONNECTOR
5 - SCREW (2)
6 - BRACKET

CS

RESTRAINTS

8O - 29

IMPACT SENSOR (Continued)

front seat cushion with another complete service
replacement package.

OPERATION

The microprocessor in the Occupant Classification

Module (OCM) contains the Occupant Classification
System (OCS) logic circuits. The OCM uses On-Board
Diagnostics (OBD) and can communicate with other
electronic modules in the vehicle as well as with a
scan tool using the Programmable Communications
Interface (PCI) data bus network. This method of
communication is also used for OCS diagnosis and
testing through the 16-way Data Link Connector
(DLC), located on the driver side lower edge of the
instrument panel.

The OCM provides a nominal five volts to both the

pressure sensor of the seat weight bladder beneath
the passenger front seat cushion and to the belt ten-
sion sensor on the passenger front seat belt lower
anchor. The OCM then monitors the return voltage
from each of the sensors. The bladder pressure sen-
sor input allows the OCM to determine whether the
passenger front seat is occupied and the relative size
of the occupant by providing a weight-sensing refer-
ence to the load on the seat cushion. The belt tension
sensor provides an additional logic input to the OCM
microprocessor that allows it to distinguish between
the lower seat belt cinch loads of a belted occupant
and the higher loads associated with a belted child
seat.

Pre-programmed decision algorithms and OCS cal-

ibration allow the OCM microprocessor to determine
when the seat cushion load as signaled by the blad-
der pressure sensor and the seat belt cinch load as
signaled by the belt tension sensor indicate that pas-
senger airbag protection is appropriate. When the
programmed conditions are met, the OCM sends the
proper electronic occupant classification messages
over the PCI data bus to the Occupant Restraint
Controller (ORC), and the ORC enables or disables
the deployment circuits for the passenger front sup-
plemental restraints. The ORC also provides a con-
trol output for the Passenger Airbag Disabled (PAD)
indicator in the instrument panel center stack, based
upon the electronic occupant classification messages
it receives from the OCM.

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 appro-
priate electronic messages to the ORC over the PCI
data bus. Then the ORC sets a DTC and sends mes-
sages to control the airbag indicator operation
accordingly. An active fault only remains for the
duration of the fault, or in some cases for the dura-

tion 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 DTC’s, 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 for-
ever.

The OCM receives battery current from an IPM

high side driver (Run/Start). The OCM receives
ground through a ground circuit of the body wire
harness, which it shares with the ORC. These con-
nections allow the OCM to be operational whenever
the ignition switch is in the Start or ON positions.

To diagnose and test the OCS, use a scan tool and

the appropriate diagnostic information.

REMOVAL

Once any of the original factory-installed compo-

nents except the Occupant Classification Module
(OCM) have been replaced with the service replace-
ment package components, the OCM can only be ser-
viced by replacing the entire passenger front seat
cushion unit with another complete service replace-
ment package (Refer to 23 - BODY/SEATS/SEAT
CUSHION - FRONT - REMOVAL).

WARNING:

Never

replace

both

the

Occupant

Restraint Controller (ORC) and the Occupant Clas-
sification Module (OCM) at the same time. If both
require replacement, replace one, then perform the
Airbag System test (Refer to 8 - ELECTRICAL/RE-
STRAINTS - DIAGNOSIS AND TESTING - AIRBAG
SYSTEM) before replacing the other. Both the ORC
and the OCM store Occupant Classification System
(OCS) calibration data, which they transfer to one
another when one of them is replaced. If both are
replaced at the same time, an irreversible fault will
be set in both modules and the OCS may malfunc-
tion and result in personal injury or death.

(1) Disconnect and isolate the battery negative

cable.

WARNING: Wait two minutes for the airbag system
reserve capacitor to discharge before beginning
any airbag system or component service. Failure to
do so may result in accidental airbag deployment,
personal injury or death.

(2) Reach under the front edge of the passenger

side front seat cushion to access and remove the lock
pin from the connector lock tower on the Occupant
Classification Module (OCM) (Fig. 36).

(3) Disconnect the passenger front seat wire har-

ness connector for the OCM.

(4) Remove the two screws that secure the OCM to

the OCM bracket.

8O - 30

RESTRAINTS

CS

OCCUPANT CLASSIFICATION MODULE (Continued)

(5) Remove the OCM from under the passenger

front seat.

INSTALLATION

WARNING: To avoid personal injury or death on
vehicles equipped with the Occupant Classification
System (OCS), only the Occupant Classification
Module (OCM) and the seat cushion trim may be
serviced separately. All other components of the
passenger front seat cushion must be serviced only
as a complete factory-calibrated, assembled and
tamper-evident service replacement package.

Once any of the original factory-installed compo-

nents except the OCM have been replaced with the
service replacement package components, the OCM
can only be serviced by replacing the entire passen-
ger side front seat cushion unit with another com-
plete service replacement package. (Refer to 23 -
BODY/SEATS/SEAT

CUSHION

-

FRONT

-

REMOVAL).

WARNING:

Never

replace

both

the

Occupant

Restraint Controller (ORC) and the Occupant Clas-
sification Module (OCM) at the same time. If both
require replacement, replace one, then perform the
Airbag System test (Refer to 8 - ELECTRICAL/RE-

STRAINTS - DIAGNOSIS AND TESTING - AIRBAG
SYSTEM) before replacing the other. Both the ORC
and the OCM store Occupant Classification System
(OCS) calibration data, which they transfer to one
another when one of them is replaced. If both are
replaced at the same time, an irreversible fault will
be set in both modules and the OCS may malfunc-
tion may result in personal injury or death.

(1) Carefully position the Occupant Classification

Module (OCM) to the OCM bracket (Fig. 36). When
the OCM is correctly positioned, the connector on the
module will be pointed to right side of the vehicle.

(2) Install the two screws to the OCM. Torque the

screws to 2 N·m (20 in. lbs.).

(3) Connect the seat wire harness connector for the

OCM. Be certain that the latches on the connector
are each fully engaged.

(4) Install the lock pin into the connector lock

tower on the OCM.

WARNING: Do not connect the battery negative
cable (Refer to 8 - ELECTRICAL/RESTRAINTS -
DIAGNOSIS AND TESTING - AIRBAG SYSTEM). Per-
sonal injury or death may result if the system test
is not performed first.

WARNING: Following successful completion of the
Airbag System test procedure, the Occupant Classi-
fication System Verification Test must be done
using a scan tool and the appropriate diagnostic
information.

(5) Verify vehicle and system operation.
(6) Close hood.

OCCUPANT RESTRAINT
CONTROLLER

DESCRIPTION

The Occupant Restraint Controller (ORC) is also

sometimes referred to as the Airbag Control Module
(ACM) (Fig. 37). The ORC is concealed beneath the
instrument panel center stack, just in front of the
floor console, where it is secured by three screws to a
stamped steel mounting bracket welded onto the top
of the floor tunnel in the passenger compartment of
the vehicle. Concealed within a hollow in the center
of the die cast aluminum ORC housing is the elec-
tronic circuitry of the ORC which includes a micro-
processor, an electronic impact sensor, an electronic
safing sensor, and an energy storage capacitor. A
stamped metal cover plate is secured to the bottom of
the ORC housing with four screws to enclose and
protect the internal electronic circuitry and compo-
nents.

Fig. 36 OCM - REMOVE/INSTALL

1 - OCCUPANT CLASSIFICATION MODULE (OCM)
2 - LOCK TOWER
3 - LOCK PIN
4 - CONNECTOR
5 - SCREW (2)
6 - BRACKET

CS

RESTRAINTS

8O - 31

OCCUPANT CLASSIFICATION MODULE (Continued)

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 right
side of the ORC housing. These two receptacles con-
nect the ORC to the vehicle electrical system through
a dedicated take out and connector of the instrument
panel wire harness, and a dedicated take out and
connector of the airbag overlay wire harness. The
ORC contains a second bi-directional safing sensor
for the curtain airbags.

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, it must be replaced. Refer to the proper Body
Diagnostic Procedures manual for diagnosis and test-
ing.

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

t 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 Instrument
Cluster and for supplemental restraint system diag-
nosis and testing through the 16-way data link con-
nector 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 cluster 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 receives battery current through two cir-

cuits; on a fused ignition switch output (RUN) circuit
through a fuse in the Integrated Power Module
(IPM), and on a fused ignition switch output (START/
RUN) circuit through a second fuse in the IPM. 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 supple-
mental restraint components for up to one second fol-
lowing 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 brackets on the outboard
sides 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 provide
verification of the direction and severity of an
impact. The ORC also monitors inputs from six addi-
tional remote side impact sensors, located in the B
and C-pillars and over the rear wheelhouse, to con-
trol the deployment of the 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. Because of the side
curtain airbags feature, a second safing sensor within

Fig. 37 ORC - LOCATION

1 - OCCUPANT RESTRAINT CONTROLLER (ORC)
2 - INSTRUMENT PANEL/PASSENGER AIRBAG
3 - ORC ELECTRICAL CONNECTORS
4 - GLOVE BOX ASSEMBLY

8O - 32

RESTRAINTS

CS

OCCUPANT RESTRAINT CONTROLLER (Continued)