2005 CHRYSLER CARAVAN seat memory

POWER SEAT SYSTEM
TABLE OF CONTENTS
page page
POWER SEAT SYSTEM
DESCRIPTION
POWER SEAT SYSTEM................31
MEMORY SYSTEM....................32
OPERATION
POWER SEAT SYSTEM................32
MEMORY SYSTEM....................33
DIAGNOSIS AND TESTING
POWER SEAT SYSTEM................33
MEMORY SYSTEM....................33
SEAT SWITCH
DESCRIPTION.........................34
OPERATION...........................34
DIAGNOSIS AND TESTING
DRIVER SEAT SWITCH.................34
REMOVAL.............................36INSTALLATION.........................36
MEMORY SWITCH
DESCRIPTION.........................36
OPERATION...........................36
DIAGNOSIS AND TESTING
MEMORY SWITCH....................37
REMOVAL.............................37
INSTALLATION.........................37
POWER SEAT TRACK
DESCRIPTION.........................37
OPERATION...........................38
DIAGNOSIS AND TESTING
POWER SEAT TRACK..................38
REMOVAL.............................38
INSTALLATION.........................39
POWER SEAT SYSTEM
DESCRIPTION
POWER SEAT SYSTEM
The power seat system option allows the driver
and front seat passenger to electrically adjust their
seating positions for optimum control and comfort.
The driver side power front seat can be adjusted in
eight different directions: up, down, front up, front
down, rear up, rear down, forward, rearward and
recliner forward and rearward. The passenger side
power front seat can be adjusted in four different
directions: forward, rearward and recliner forward
and rearward.
The power seat system receives battery current
through a 40 amp fuse in the Integrated Power Mod-
ule (IPM) and a 30 amp circuit breaker under the
seat so that the power seats remain operational,
regardless of the ignition switch position.
WARNING: SOME VEHICLES ARE EQUIPPED WITH
SEATBACK MOUNTED AIRBAGS (Fig. 1). BEFORE
ATTEMPTING TO DIAGNOSE OR SERVICE ANY
SEAT OR POWER SEAT SYSTEM COMPONENT
YOU MUST FIRST DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE CABLE. THEN WAIT TWO MIN-
UTES FOR THE SYSTEM CAPACITOR TO DIS-
CHARGE BEFORE FURTHER SYSTEM SERVICE.
THIS IS THE ONLY SURE WAY TO DISABLE THE
AIRBAG SYSTEM. FAILURE TO DO SO COULDRESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
The eight-way driver side power seat is also avail-
able with the heated seat and/or memory seat sys-
tem. The memory seat system automatically
positions the power seat for two different drivers.
Fig. 1 IDENTIFYING A SIDE AIRBAG EQUIPPED
SEAT
1 - AIRBAG LABEL
RSPOWER SEAT SYSTEM8N-31

(Refer to 8 - ELECTRICAL/HEATED SEATS -
DESCRIPTION) for more information on the heated
seat option. (Refer to 8 - ELECTRICAL/POWER
SEATS - DESCRIPTION - MEMORY SEAT SYS-
TEM) for more information on the memory seat sys-
tem.
The power seat system includes the following com-
ponents:
²Power seat recliners
²Power seat switches
²Power seat tracks
²Circuit breaker
The power seat system with memory and heated
seat options includes the following components:
²Power seat recliner
²Power seat switch
²Power seat track.
²Memory Seat Mirror Module (MSMM)
²Memory set switch
²Heated Seat Module (HSM)
²Heated seat switch
²Electronic Vehicle Information Center (EVIC)
MEMORY SYSTEM
The memory system is able to store and recall the
driver side power seat positions (including the power
recliner position), power adjustable pedal positions
and the driver outside mirror position for two driv-
ers. On vehicles equipped with a factory radio, the
memory system is also able to store and recall radio
station presets for two drivers. The memory system
also will store and recall the last station listened to
for each driver, even if it is not one of the preset sta-
tions.
The memory system will automatically return to
its preset settings when the corresponding numbered
button of the memory switch is depressed, or when
the doors are unlocked using the corresponding
Remote Keyless Entry (RKE) transmitter. A customer
programmable feature of the memory system allows
the RKE recall of memory features to be disabled, if
desired. This programmable feature is internal in the
Electronic Vehicle Information Center (EVIC) mod-
ule, which is located in the overhead console.
A Memory Seat Mirror Module (MSMM) is used to
control and integrate the many electronic functions
and features included in the memory seat and mirror
systems.
The memory system includes the following compo-
nents:
²Memory Seat Mirror Module (MSMM)
²Memory set switch
²Position potentiometers on the driver outside
side view mirror
²Position potentiometers on the power adjustable
pedal motor²Position potentiometers on the driver side power
seat track and power seat recliner motors
²Electronic Vehicle Information Center (EVIC)
²Radio receiver (if PCI data bus capable)
Certain functions of the memory system rely upon
resources shared with other electronic modules in the
vehicle over the Programmable Communications
Interface (PCI) data bus network. Initial diagnosis of
these electronic modules or the PCI data bus network
requires the use of a DRBIIItor equivalent scan tool
and the proper Diagnostic Procedures information. If
this method does not prove conclusive, the proper
wiring schematics and the service manual diagnostic
information are required.
The other electronic modules that may affect mem-
ory system operation are:
²Body Control Module (BCM)- (Refer to 8 -
ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/BODY CONTROL/CENTRAL TIMER MODUL
- DESCRIPTION) for additional information.
²Powertrain Control Module (PCM)- (Refer
to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/POWERTRAIN CONTROL MODULE -
DESCRIPTION) for additional information.
²Transmission Control Module (TCM)- (Refer
to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/TRANSMISSION CONTROL MODULE -
DESCRIPTION) for additional information.
(Refer to 8 - ELECTRICAL/HEATED SEATS -
DESCRIPTION) for additional information on the
heated seat system. (Refer to 8 - ELECTRICAL/
POWER LOCKS - DESCRIPTION) for additional
information on the RKE system.
OPERATION
POWER SEAT SYSTEM
The power seat system receives battery current
through fuse #22 in the Integrated Power Module
(IPM) and a circuit breaker under the front seats,
regardless of the ignition switch position.
When a power seat switch control knob or knobs
are actuated, a battery feed and a ground path are
applied through the switch contacts to the appropri-
ate power seat track adjuster motor. The selected
adjuster motor operates to move the seat track
through its drive unit in the selected direction until
the switch is released, or until the travel limit of the
seat track is reached. When the switch is moved in
the opposite direction, the battery feed and ground
path to the motor are reversed through the switch
contacts. This causes the adjuster motor to run in the
opposite direction.
No power seat switch should be held applied in any
direction after the seat track has reached its travel
limit. The power seat adjuster motor each contain a
8N - 32 POWER SEAT SYSTEMRS
POWER SEAT SYSTEM (Continued)

self-resetting circuit breaker to protect them from
overload. However, consecutive or frequent resetting
of the circuit breaker must not be allowed to con-
tinue, or the motor may be damaged.
MEMORY SYSTEM
The Memory Seat Mirror Module (MSMM) receives
battery current through fuse #22 in the Integrated
Power Module (IPM) and the power seat system cir-
cuit breaker, located under the driver side front seat
near the rear edge of the seat cushion pan. The mem-
ory system does not operate with the Ignition-Off
Draw (IOD) fuse removed. The MSMM will drive a
maximum of 2 motors at a time in a given direction.
If conflicting directions are requested, the priority for
response will be approximately as follows:
²Seat Track Rearward or Forward
²Seat Front Down or Up
²Seat Rear Down or Up
²Recliner Rearward or Forward
The inputs from these switches to the MSMM is a
current limited battery source fed by the MSMM.
This protects the MSMM printed circuit board traces
from acting as fuses. All of these switch contact
inputs to the MSMM are normally closed to ground,
except when actuated.
For diagnosis of the MSMM, the Programmable
Communication Interface (PCI) data bus, or the other
electronic modules on the PCI data bus that provide
inputs and outputs for the memory system, the use of
a DRBIIItor equivalent scan tool and the proper
Diagnostic Procedures information is recommended.
ELECTRONIC VEHICLE INFORMATION CENTER
The Electronic Vehicle Information Center (EVIC)
serves as the user interface for the memory system.
It displays memory system status messages and pro-
vides the user with the means for enabling and dis-
abling the many customer programmable features
available on the vehicle, including those for the mem-
ory system.
(Refer to 8 - ELECTRICAL/OVERHEAD CON-
SOLE/ELECTRONIC VEHICLE INFO CENTER -
DESCRIPTION) for additional information on the
EVIC.
DIAGNOSIS AND TESTING
POWER SEAT SYSTEM
Following are tests that will help to diagnose the
hard wired components and circuits of the power seat
system. However, if the vehicle is also equipped with
the optional memory system, these tests may not
prove conclusive in the diagnosis of the driver side
power seat. In order to obtain conclusive testing ofthe driver side power seat with the memory system
option, the Programmable Communications Interface
(PCI) data bus network and all of the electronic mod-
ules that provide inputs to, or receive outputs from
the memory system components must be checked,
(Refer to 8 - ELECTRICAL/POWER SEATS - DIAG-
NOSIS AND TESTING).
WARNING: SOME VEHICLES ARE EQUIPPED WITH
SEATBACK MOUNTED AIRBAGS. BEFORE
ATTEMPTING TO DIAGNOSE OR SERVICE ANY
SEAT OR POWER SEAT SYSTEM COMPONENT
YOU MUST FIRST DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE CABLE. THEN WAIT TWO MIN-
UTES FOR THE SYSTEM CAPACITOR TO DIS-
CHARGE BEFORE FURTHER SYSTEM SERVICE.
THIS IS THE ONLY SURE WAY TO DISABLE THE
AIRBAG SYSTEM. FAILURE TO DO SO COULD
RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT
AND POSSIBLE PERSONAL INJURY.
(1) If either power seat is completely inoperable,
check the power seat circuit breaker, located under
the trailing edge of the driver side power seat. If the
power seat circuit breaker is OK, continue to the
next step.
(2) Check for proper battery and ground connec-
tions at the power seat switch and/or memory seat
module. Repair any wiring as necessary.
(3) Check the power seat system wire harness con-
nections and pins to ensure proper circuit continuity
and ground paths.
MEMORY SYSTEM
In order to obtain conclusive testing of the memory
system, the Programmable Communications Interface
(PCI) data bus network and all of the electronic mod-
ules that provide inputs to, or receive outputs from
the memory system components must be checked.
The most reliable, efficient, and accurate means to
diagnose the driver side power seat with the memory
system option requires the use of a DRBIIItor
equivalent scan tool and the proper Diagnostic Proce-
dures information. The DRBIIItscan tool can pro-
vide confirmation that the PCI data bus is functional,
that all of the electronic modules are sending and
receiving the proper messages on the PCI data bus,
and that the memory system is receiving the proper
hard wired inputs and relaying the proper hard
wired outputs to perform its driver side power seat
functions.
(1) If the driver power seat exhibits an interrupted
or jerky motion, ensure the wire harness is connected
correctly. To verify the concern, obtain a DRB IIItor
equivalent scan tool and energize each axis one at a
time. If any axis stops in approximately 2 seconds
(without hitting the end of travel), the feedback for
RSPOWER SEAT SYSTEM8N-33
POWER SEAT SYSTEM (Continued)

REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Using a push pin remover or other suitable
wide flat-bladed tool, gently pry the power seat and
power recliner switch knobs off of the switch levers
(Fig. 4).
(3) Remove the screws that secure the outboard
seat cushion side cover to the seat cushion frame,
(Refer to 23 - BODY/SEATS/SEAT CUSHION SIDE
COVERS - REMOVAL).
(4) Pull the outboard seat cushion side cover away
from the seat cushion frame far enough to access the
power seat switch wire harness connector.
(5) Disconnect the power seat wire harness connec-
tor from the power seat switch connector receptacle.
(6) Remove the screws that secure the power seat
switch to the inside of the outboard seat cushion side
cover.
(7) Remove the power seat switch from the out-
board seat cushion side cover.
INSTALLATION
(1) Position the power seat switch onto the out-
board seat cushion side cover.
(2) Install and tighten the screws that secure the
power seat switch to the inside of the outboard seat
cushion side cover. Tighten the screws to 1.5 N´m (14
in. lbs.).
(3) Reconnect the power seat wire harness connec-
tor to the power seat switch connector receptacle.(4) Install the outboard seat cushion side cover,
(Refer to 23 - BODY/SEATS/SEAT CUSHION SIDE
COVERS - INSTALLATION).
(5) Install the power seat and power recliner
switch knobs onto the switch control levers.
(6) Reconnect the battery negative cable.
MEMORY SWITCH
DESCRIPTION
Vehicles equipped with the memory system have a
memory switch mounted to the driver side front door
trim panel (Fig. 5). This switch is used to set and recall
all of the memory system settings for up to two drivers.
The memory switch is a resistor multiplexed unit that
is hard wired to the Body Control Module (BCM). The
BCM sends out the memory system set and recall
requests to the other electronic modules over the Pro-
grammable Communications Interface (PCI) data bus.
The memory switch cannot be adjusted or repaired
and, if faulty or damaged, it must be replaced.
OPERATION
The memory switch has three momentary switch
buttons labeled Set, 1 and 2. When the memory set
switch is depressed, a resistance value is sent to the
Body Control Module (BCM) via hard wired connec-
tions. When the memory system is in ªsetº mode a
chime will be generated by the BCM.
Fig. 4 REMOVING SWITCH CONTROL KNOBS -
TYPICAL
Fig. 5 MEMORY SWITCH LOCATION
1 - MEMORY SWITCH
2 - SWITCH BEZEL
8N - 36 POWER SEAT SYSTEMRS
SEAT SWITCH (Continued)

DIAGNOSIS AND TESTING
MEMORY SWITCH
(1) Remove the memory switch from the drivers
door panel (Refer to 8 - ELECTRICAL/POWER
SEATS/MEMORY SET SWITCH - REMOVAL).
(2) Using an ohmmeter, check the continuity of the
memory select switch MUX circuit between the C2
wire harness connector for the Body Control Module
(BCM) and the wire harness connector for the mem-
ory switch. There should be continuity. If OK, go to
Step 3. If not OK, repair the open or shorted MUX
circuit as required.
(3) Using an ohmmeter, check the continuity of the
memory select switch return circuit between the C2
wire harness connector for the BCM and the wire
harness connector for the memory switch. There
should be continuity. If OK, go to Step 4. If not OK,
repair the open or shorted return circuit as required.
(4) Using an ohmmeter, test the resistances of the
memory switch, refer to the MEMORY SWITCH
TEST TABLE. If OK, (Refer to 8 - ELECTRICAL/
POWER SEATS - DIAGNOSIS AND TESTING -
MEMORY SYSTEM). If not OK, replace the memory
switch, (Refer to 8 - ELECTRICAL/POWER SEATS/
MEMORY SET SWITCH - REMOVAL).
MEMORY SWITCH TEST TABLE
MEMORY
SWITCH
POSITIONRESISTANCE
BETWEEN
PINSRESISTANCE
RANGE
(OHMS)
NEUTRAL 1&2 24650   5%
(24.65 k)
MEMORY 1 1&2 6850   5%
(6.85 k)
MEMORY 2 1&2 2100   5%
(2.10 k)
SET 1&2 4490   5%
(4.49 k)
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the front door trim panel switch bezel
from the driver side front door. Using a thin flat-
bladed pry tool, gently pry the switch bezel away
from the drivers door trim panel.
(3) Disconnect the memory switch wire harness
connector from the memory switch.
(4) Remove the two screws that secure the memory
switch to the back of the driver side front door trim
panel switch bezel.
(5) Remove the memory switch.
INSTALLATION
(1) Position the memory switch and install and
tighten the two screws that secure the memory
switch to the back of the driver side front door trim
panel switch bezel. Tighten the screws to 2.2 N´m (20
in. lbs.).
(2) Reconnect the memory switch wire harness
connector to the memory switch.
(3) Install the trim panel switch bezel onto the
driver side front door.
(4) Reconnect the battery negative cable.
POWER SEAT TRACK
DESCRIPTION
The power seat option includes an electrically oper-
ated power seat track located under the front seat. If
equipped with Memory System, the front power seat
track on the driver side of the vehicle also provides
the mounting location for the Memory Seat/Mirror
Module (MSMM). The power seat circuit breakers are
mounted on the rear of the power seat track, just
behind the seat rear trim panel. The lower half of the
power seat track is secured to the floor panel via four
studs and nuts that must be accessed from the
underside of the vehicle. Four bolts secure the bot-
tom of the seat cushion pan to the upper half of the
power seat track unit. Four additional bolts secure
the seat back frame to the power seat track unit.
The eight-way power seat track unit includes four
reversible electric motors that are secured to the
upper half of the track unit. Each motor moves the
seat adjuster through a combination of worm-drive
gearboxes and screw-type drive units. Each of the
four power seat track motors used on models
equipped with the optional memory system incorpo-
rate a position potentiometer integral to the motor
assembly, which electronically monitors the motor
position. This enables the memory system to function
by referencing the motor positions programmed into
the memory seat/mirror module.
The front and rear of the seat are operated by two
separate vertical adjustment motors. These motors
can be operated independently of each other, tilting
the entire seat assembly forward or rearward. They
can also be operated in unison by selecting the
proper power seat switch functions, which will raise
or lower the entire seat assembly. A third motor is
the horizontal adjustment motor, which moves the
seat track in the forward and aft directions. The
forth motor is the recliner adjustment motor, which
moves the seat back in the forward and rearward
directions.
The four-way power seat track unit includes two
reversible electric motors that are secured to the
RSPOWER SEAT SYSTEM8N-37
MEMORY SWITCH (Continued)

(2) Remove the appropriate seat from the vehicle
and place it on a clean work surface, (Refer to 23 -
BODY/SEATS/SEAT - REMOVAL).
(3) Remove the Memory Seat/Mirror Module
(MSMM) mounting fasteners (if equipped).
(4) Disconnect the MSMM electrical harness con-
nectors and remove the MSMM from the power seat
track (if equipped).
(5) Remove the front seat track rear cover, (Refer
to 23 - BODY/SEATS/SEAT TRACK REAR COVER -
REMOVAL).
(6) Remove the seat side cover and power seat
switch as an assembly (Refer to 23 - BODY/SEATS/
SEAT CUSHION SIDE COVERS - REMOVAL).
(7) Disconnect all electrical connectors connecting
the power seat track to the seat assembly.
(8) Pull the seat back trim cover up slightly to
access and remove the two seat back frame mounting
bolts and also remove two seat back recliner bolts.
(9) Remove four seat track mounting bolts from
the seat cushion pan.
(10) Remove the power seat track from the seat.INSTALLATION
(1) Position the seat cushion on the seat track.
(2) Install the four seat track retaining bolts in the
seat cushion pan. Torque the bolts to 28.5 N´m (21 ft-
lbs.).
(3) Position the seat back and install the two seat
back frame mounting bolts and the two seat back
recliner bolts. Torque the bolts to 55 N´m (40.5
ft-lbs.).
(4) Route and connect the electrical connectors
between the power seat track and the seat assembly.
(5) Install the seat side cover and power seat
switch as an assembly (Refer to 23 - BODY/SEATS/
SEAT CUSHION SIDE COVERS - INSTALLATION).
(6) Install the front seat track rear cover, (Refer to
23 - BODY/SEATS/SEAT TRACK REAR COVER -
INSTALLATION).
(7) Position the Memory Seat/Mirror Module
(MSMM) and connect the MSMM electrical connec-
tors (if equipped).
(8) Install the MSMM mounting fasteners (if
equipped).
(9) Install the seat assembly in the vehicle (Refer
to 23 - BODY/SEATS/SEAT - INSTALLATION).
(10) Connect the battery negative cable.
RSPOWER SEAT SYSTEM8N-39
POWER SEAT TRACK (Continued)

driver and the front seat passenger to the structure
of the instrument panel (Refer to 8 - ELECTRICAL/
RESTRAINTS/KNEE BLOCKER AIRBAG -
DESCRIPTION). The seat belt tensioners remove the
slack from the front seat belts to provide further
assurance that the driver and front seat passenger
are properly positioned and restrained for an airbag
deployment.
When the ORC monitors a problem in any of the
dual front airbag system circuits or components,
including the seat belt tensioners, it stores a Diag-
nostic Trouble Code (DTC) in its memory and sends
an electronic message to the EMIC to turn on the
airbag indicator. Proper testing of the supplemental
restraint system components, the Programmable
Communications Interface (PCI) data bus, the elec-
tronic message inputs to and outputs from the EMIC
or the ORC, as well as the retrieval or erasure of a
DTC from the ORC or the EMIC requires the use of
a scan tool. Refer to the appropriate diagnostic infor-
mation.
OCCUPANT CLASSIFICATION SYSTEM
The Occupant Classification System (OCS) auto-
matically suppresses or enables passenger airbag and
seat belt tensioner operation based upon whether or
not the passenger side front seat is occupied and, if
the seat is occupied, classifies the size of the occu-
pant and whether the seat is occupied by a child
seat.
The OCS has an Occupant Classification Module
(OCM) that monitors inputs from the seat weight
bladder pressure sensor under the passenger side
front seat cushion and from the belt tension sensor
on the passenger side front seat belt lower anchor.
Based upon those inputs the microprocessor within
the OCM classifies the occupant of the passenger
side front seat. The OCM then sends electronic occu-
pant classification messages to the ORC. The micro-
processor and programming of the ORC uses these
occupant classification messages to determine
whether to enable or disable the deployment circuits
for the passenger airbag and seat belt tensioner.
The OCS electrical circuits and components are
continuously monitored by the OCM, and the OCM is
continuously monitored by the ORC. A passenger air-
bag ON/OFF indicator is located in the instrument
panel center stack area. This indicator receives bat-
tery current whenever the ignition switch is in the
ON or START positions, and illuminates only when
the ORC pulls the indicator control circuit to ground.
The indicator illuminates for about seven seconds as
a bulb test each time the ignition switch is turned to
the ON or START positions. Following the bulb test,
the indicator is turned ON or OFF by the ORC based
upon the electronic occupant classification messagesreceived from the OCM. This indicator is illuminated
whenever the passenger airbag and seat belt ten-
sioner operation has been suppressed, and is turned
OFF whenever they are enabled or when the passen-
ger seat is classified as empty.
When the OCM monitors a problem in any of the
OCS circuits or components, it stores a fault code or
DTC in its memory circuit and sends an electronic
message to the ORC. The ORC then sends an elec-
tronic message to the EMIC to turn ON the airbag
indicator. If for any reason the OCM is unable to
classify the occupant it sends an electronic message
to the ORC, and the ORC suppresses passenger air-
bag and seat belt tensioner operation. Proper testing
of the OCS components, the Programmable Commu-
nications Interface (PCI) data bus, the electronic
message inputs to and outputs from the OCM, the
EMIC or the ORC, as well as the retrieval or erasure
of a DTC's, requires the use of a scan tool. Refer to
the appropriate diagnostic information.
WARNING
WARNINGS
Disconnect and isolate the battery negative
cable before beginning any airbag system com-
ponent diagnosis, testing, removal, or installa-
tion procedures. Allow system capacitor to
discharge for two minutes before beginning any
component testing or service. This will disable
the airbag system. Failure to disconnect the
battery negative cable may result in accidental
airbag deployment, personal injury, or death.
Do not place an intact undeployed airbag
face down on a solid surface. The airbag will
propel into the air if accidentally deployed and
may result in personal injury or death.
When carrying or handling an undeployed
airbag, the trim side (face) of the airbag should
be pointing towards the body to minimize pos-
sibility of injury if accidental deployment
occurs. Failure to do this may result in per-
sonal injury or death.
Replace airbag system components with
Mopartreplacement parts. Substitute parts
may appear interchangeable, but internal dif-
ferences may result in inferior occupant protec-
tion. Failure to do so may result in occupant
personal injury or death.
Wear safety glasses, rubber gloves, and long
sleeved clothing when cleaning powder residue
from vehicle after airbag deployment. Sodium
hydroxide powder residue emitted from a
deployed airbag can cause skin irritation.
Flush affected area with cool water if irritation
is experienced. If nasal or throat irritation is
RSRESTRAINTS8O-5
RESTRAINTS (Continued)

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
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
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
RSRESTRAINTS8O-25