Dodge Nitro. Manual - part 240

OCCUPANT CLASSIFICATION MODULE 

Fig. 46: Occupant Classification Module 
Courtesy of CHRYSLER LLC 

The Occupant Classification Module (OCM) (1) is secured with two screws to a stamped metal bracket on the 
inboard passenger side front seat riser beneath the seat cushion. 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. 

Four mounting tabs (2) and two connector receptacles (3) are integral to the OCM housing. The two mounting 
tabs designed to accept self tapping screws are used to secure the module to the mounting bracket, while the 
remaining two mounting tabs are unused in this application. The connector receptacles contain terminal pins 
that connect the OCM to the vehicle electrical system through dedicated take outs and connectors of the 
passenger side front seat wire harness. 

The OCM and all of the other components of the Occupant Classification System (OCS) including the 
passenger side front seat, the seat weight sensors, 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. 

The OCM cannot be adjusted or repaired and, if damaged or ineffective, it must be replaced. The OCM 
software is flash programmable. A non-calibrated OCM is available for separate service replacement. 

OPERATION 

OCCUPANT CLASSIFICATION MODULE 

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 the diagnostic scan tool using the Controller Area Network (CAN) data 

 

2007 Dodge Nitro R/T 

2007 RESTRAINTS Service Information - Nitro

  

bus. This method of communication is also used for OCS diagnosis and testing through the 16-way data link 
connector located on the driver side lower edge of the instrument panel. 

The OCM provides voltage to the four seat weight sensors located on the corners of the passenger side front 
seat. The OCM then monitors return inputs from each of the sensors on dedicated hard wired data 
communication circuits. The seat weight sensor inputs allow the OCM to determine whether the passenger side 
front seat is occupied and the relative size of the occupant by providing a weight-sensing reference to the load 
on the seat. 

Pre-programmed decision algorithms and OCS calibration allow the OCM microprocessor to determine when 
passenger airbag protection is appropriate based upon the seat load as signaled by the seat weight sensors. When 
the programmed conditions are met, the OCM sends the proper electronic occupant classification messages 
over the CAN data bus to the Occupant Restraint Controller (ORC), and the ORC controls the deployment 
circuits for the passenger side front supplemental restraints. On vehicles so equipped, the ORC also provides a 
control output for the passenger airbag on/off indicator in the instrument panel 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 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 B(+) circuit through a fuse in the Totally Integrated Power 
Module (TIPM) and receives electronic ignition switch status messages indicating the ignition switch position 
over the CAN data bus. The OCM receives ground through a ground circuit and take out of the body wire 
harness. These connections allow the OCM to be operational whenever the ignition switch is in the ON or 
START positions. 

The hard wired inputs and outputs for the OCM 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 OCM or the electronic controls and communication between other 
modules and devices that provide features of the OCS. The most reliable, efficient, and accurate means to 
diagnose the OCM or the electronic controls and communication related to OCM operation requires the use of a 
diagnostic scan tool. Refer to the appropriate diagnostic information. 

REMOVAL 

OCCUPANT CLASSIFICATION MODULE 

WARNING:

To avoid serious or fatal injury on vehicles equipped with airbags, disable 
the Supplemental Restraint System (SRS) before attempting any steering 
wheel, steering column, airbag, Occupant Classification System (OCS), 
seat belt tensioner, impact sensor, or instrument panel component 

 

2007 Dodge Nitro R/T 

2007 RESTRAINTS Service Information - Nitro

  

Fig. 47: Identifying Occupant Classification Module (OCM), Inboard Passenger Side Front Seat Riser, 
Screws & Mounting Bracket 
Courtesy of CHRYSLER LLC 

1. Disconnect and isolate the battery negative cable. Wait two minutes for the system capacitor to discharge 

before further service.  

2. Reach under the front edge of the passenger side front seat cushion to access and disconnect the two seat 

wire harness connectors from the Occupant Classification Module (OCM) (1) connector receptacles 
located on the forward-facing end of the module.  

3. Remove the two screws (3) that secure the OCM to the top of the mounting bracket (4) on the inboard 

passenger side front seat riser (2).  

4. Remove the OCM from under the passenger side front seat cushion.  

INSTALLATION 

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 SRS. 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 replacement. The OCM and all of the other components of the 
Occupant Classification System (OCS) including the passenger side front seat, 
the seat weight sensors, and the passenger 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.

 

2007 Dodge Nitro R/T 

2007 RESTRAINTS Service Information - Nitro

  

OCCUPANT CLASSIFICATION MODULE 

Fig. 48: Identifying Occupant Classification Module (OCM), Inboard Passenger Side Front Seat Riser, 
Screws & Mounting Bracket 
Courtesy of CHRYSLER LLC 

1. Reach under the front edge of the passenger side front seat cushion to carefully position the Occupant 

Classification Module (OCM) (1) to the top of the mounting bracket (4) on the inboard passenger side 
front seat riser (2). When the OCM is correctly positioned, the connector receptacles on the module will 
be pointed forward.  

2. Install and tighten the two screws (3) that secure the OCM to the mounting bracket. Tighten the screws to 

WARNING:

To avoid serious or fatal injury on vehicles equipped with airbags, disable 
the Supplemental Restraint System (SRS) before attempting any steering 
wheel, steering column, airbag, Occupant Classification System (OCS), 
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 SRS. 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 replacement. The OCM and all of the other components of the 
Occupant Classification System (OCS) including the passenger side front seat, 
the seat weight sensors, and the passenger 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.

 

2007 Dodge Nitro R/T 

2007 RESTRAINTS Service Information - Nitro