Part 2

OCCUPANT CLASSIFICATION SYSTEM
A non-calibrated Occupant Classification Module (OCM) is the only component of the Occupant Classification System (OCS) that is available for separate service replacement, as outlined in the procedures that follow. The OCS components of the passenger side front seat cushion including the cushion frame, springs, pad, seat weight bladder and pressure sensor, seat cushion foam and the OCM are a factory-calibrated and assembled unit. Once this unit is connected to a vehicle electrically, the calibration settings are uploaded from the OCM and stored in the memory of the Airbag Control Module (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. If any of the remaining OCS components of the passenger side, front seat cushion require replacement, they are serviced only as a factory calibrated, assembled, and tamper-evident service replacement package. This package includes the assembled frame, springs, pad, seat weight bladder and pressure sensor, foam, wiring and a calibrated OCM. When installing this package, always replace all of the existing components with the new components as a unit. Do not attempt to separate or disconnect any of the new OCS components contained in the service replacement package from each other, and do not attempt to reuse any of the replaced components in this or any other vehicle. Once any of the original factory-installed components except the OCM have been replaced with the service replacement package components, the OCM can only be serviced by replacing the entire passenger side front seat cushion unit with another complete service replacement package.

CAUTION: On vehicles equipped with the Occupant Classification System (OCS), never replace both the Airbag Control Module (ORC) and the Occupant Classification Module (OCM) at the same time. If both require replacement, replace one. Then perform the supplemental restraint verification test before replacing the other. Both the ORC and the OCM store 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.

The OCM is subsystem of the Airbag Control Module (ORC). Therefore the OCM bus message updates the ORC with the front passenger seat information via PCI Bus message. The ORC then controls the Passenger Off indicator and the Airbag Warning Indicator to provide system onboard diagnostic feedback. All OCS wiring repairs are prohibited; when wiring problems are diagnosed a Bladder Repair Kit is the only approved repair.

PASSENGER AIRBAG OFF INDICATOR
Vehicles equipped with the Occupant Classification System (OCS) include a passenger airbag off indicator located in the Switch Bank in the center of the instrument panel. Vehicles without OCS have a blank lens installed in the instrument panel. At ignition on, for a system test, the ORC low side driver grounds a yellow Light Emitting Diode (LED) circuit causing the PASS AIRBAG OFF Indicator text and icon to be illuminated.

SEAT WEIGHT SENSOR
Vehicles equipped with the Occupant Classification System (OCS) have a seat weight bladder and pressure sensor unit that is integral to the passenger front seat cushion. The pressure sensor receives a nominal five volts and a ground through dedicated hardwired circuits from the OCM. The OCM then monitors the pressure sensor output voltage.

SEAT BELT TENSION SENSOR - BTS
The Belt Tension Sensor (BTS) is designed to measure belt tension as an input to a passenger Occupant Classification System (OCS). It is used to detect high cinch loads associated with child seats and compensate for the seat cushion load to correctly classify occupant size. When a load is applied to the seat belt, the belt tension sensor measures the load. As the load changes, the circuitry of the belt tension sensor changes the output voltage of the sensor. The belt tension sensor receives a nominal five volts and a ground through dedicated hardwired circuits from the OCM. The OCM then monitors the belt tension sensor output voltage on a dedicated hardwired data communication circuit. If the vehicle has experienced any impact(s) resulting in deployment of a pyrotechnic device of any kind (airbag, seatbelt tensioner, side curtain, etc.) within the vehicle, the entire passenger seat belt retractor assembly, including the BTS, shall be replaced. Additionally, if the seat belt webbing has become cut, frayed, or worn; or if the stitching has become damaged in any way, the entire passenger seat belt retractor assembly, including the BTS, shall be replaced. The belt tension sensor cannot be repaired and, if faulty or damaged, the entire passenger side front seat belt and retractor unit must be replaced. The OCM Verification Test will also provide a BTS Verification procedure to verify the BTS function. This verification procedure requires the Miller Special Tool #8828.

BLADDER REPAIR KIT
There are only three replaceable components in the OCS, Occupant Classification Module, Bladder Repair Kit and the Passenger Airbag OFF Indicator. The Bladder repair kit contains the OCS bladder, wire harnesses, pressure sensor (SeatWeight Sensor), module, seat cushion and other related structural and sound deadening components. The module and sensor connector must have a Tamper Evident material installed on the service kit module and sensor connectors. This material provides visible evidence that the assembly has been separated after the calibration process was completed. Do not install a Bladder Repair Kit if it appears that any of the components have been disconnected. The OCM can be replaced if the Airbag Control Module has uploaded the seat calibration into memory in a previous ignition cycle and the new OCM has a blank VIN and no calibration data stored in memory.

NOTE:
- An OCM can only be replaced in a passenger front seat if the seat is equipped with the original OCS module, bladder, sensor and wiring.
- Servicing the OCS may create additional active and stored trouble codes that must be resolved before the vehicle can be returned to the owner. The OCS Verification Test will also set active DTCs if the procedure is not completed successfully.

The Miller Special Tool, MRL-9077 and the DRBIII(R) are needed to successfully complete the system Verification Test. The DRBIII(R) may report the following errors and failure messages during the procedure.

NEW DRBIII(R) FEATURES

ORC Menu
The DRBIII(R) ORC System Test screen will display the following:
VIN verification - Original VIN and Current VIN
PCM Monitor - PCM Active On The Bus or PCM
Not Active On The Bus

The DRBIII(R) ORC Input/Outputs screen will display the following:
- OCM Status:
- Seat Class 0 (Empty)
- Seat Class 1 (Rear Facing Infant car Seat or RFIS)
- Seat Class 2 (6 year old or Child)
- Seat Class 3 (greater than or equal to 5th Percentile Female)
- Seat Class 4 (less than 5th Percentile Female)
- Seat Class 5 (Undetermined)

The DRBIII(R) ORC Miscellaneous screen will display the following:
- Configure Airbag On-Off Switch
1. No Airbag On-Off Switch
2. Pass OCM Only

OCS Menu
The DRBIII(R) OCM Input/Output screen will display the following:
- OCS Status --- 90, 919, 929, 939, 949, 959

The DRBIII(R) OCM Sensors screen will display the following:
- Bladder Output --- XXX A/D counts
- Pas BTS Output --- XXX A/D counts

The DRBIII(R) OCM OCS Info Monitor screen will display the following:
- Pass BTS -- Enabled or Disabled

System Verification
The DRBIII(R) OCM System Test screen will display the following
- PCM Monitor - PCM Active On The Bus or PCM Not Active On The Bus
- Clear VIN Mismatch - Clear VIN Mismatch Complete
- VIN Verification - Original VIN and Current VIN Clear VIN Mismatch
- OCS Verification - OCS Verification

Test process errors:
Test In Progress
Mode 33 Not Supported
Subfunction not supported
Test Busy - Repeat Test
Conditions for Test Not Correct
Routine Already Running
Routine was Never Started
Press any key to continue, then restart the verification test.

Test failed conditions:
Test Failed - Active DTCs Present
Test Failed - Seat is Empty
Test Failed - Seat Occupied
Test Failed - Weight Above Threshold
Test Failed - Weight Below Threshold
Test Failed - Temperature Out of Range
Test Failed - Seat Pressure Too High
Test Failed - Seat Pressure Too Low
Test Failed - Seat Pressure Not Stable
Test Failed - Temperature Out of Range
Test Failed - Seat Pressure Too Low
Test Failed - Power Up Time Too Short
Test Failed - Power Up Time Too Long
Test Failed - K Empty Count is 0
Test Failed - No EOL Calibration
Test Failed - K Allow is FF
Allow the vehicle seat and interior temperature to stabilize, check voltage supplies and repair any other active DTCs before restarting the System Verification test.

The OCS has been Verified or The OCS has NOT been Verified

WARNING:
- TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.
- TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION ON, THEN RECONNECT THE BATTERY.
- TO AVOID PERSONAL INJURY OR DEATH ON VEHICLES EQUIPPED WITH THE OCCUPANT CLASSIFICATION SYSTEM (OCS), ONLY THE OCCUPANT CLASSIFICATION MODULE (OCM) AND THE PASSENGER SEAT BLADDER AND CUSHION SERVICE KIT ARE THE ONLY PARTS SERVICED.
- IF THE OCCUPANT CLASSIFICATION MODULE IS DROPPED AT ANY TIME, IT MUST BE REPLACED. FAILURE TO TAKE THE PROPER PRECAUTIONS CAN RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND PERSONAL INJURY OR DEATH. 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 SIDE FRONT SEAT CUSHION ASSEMBLY MUST BE SERVICED ONLY AS A COMPLETE FACTORY-CALIBRATED, ASSEMBLED AND TAMPER-EVIDENT SERVICE REPLACEMENT PACKAGE. THIS PACKAGE INCLUDES THE FRAME, SPRINGS, PAD, BLADDER AND PRESSURE SENSOR, FOAM, WIRING AND A CALIBRATED OCM. WHEN INSTALLING THIS PACKAGE ALWAYS REPLACE ALL OF THE EXISTING COMPONENTS WITH THE NEW COMPONENTS AS A UNIT. DO NOT ATTEMPT TO SEPARATE OR DISCONNECT ANY OF THE NEW OCS COMPONENTS IN THE SERVICE REPLACEMENT PACKAGE FROM EACH OTHER, AND DO NOT ATTEMPT TO REUSE ANY OF THE REPLACED COMPONENTS IN THIS OR ANY OTHER VEHICLE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN FAILURE OF THE PASSENGER AIRBAG TO DEPLOY WHEN REQUIRED, OR IN PASSENGER AIRBAG DEPLOYMENT WHEN NOT REQUIRED.

SPECIAL TOOLS
Some airbag diagnostic tests will require the use of special tools, airbag load tools, 8443 for testing squib circuits and the Occupant Classification Seat Weight Tool 9077. The load tools contain fixed resistive loads, jumpers and adapters. The fixed loads are connected to cables and mounted in a storage case. The cables can be directly connected to some airbag system connectors. Jumpers are used to convert the load tool cable connectors to the other airbag system connectors. The adapters are connected to the module harness connector to open shorting clips and protect the connector terminal during testing. When using the load tool follow all of the safety procedures in the service information for disconnecting airbag system components. Inspect the wiring, connector and terminals for damage or misalignment. Substitute the airbag load tool in place of a Driver or Passenger Airbag, curtain airbag, clockspring, or seat belt tensioner (use a jumper if needed). Then follow all of the safety procedures in the service information for connecting airbag system components. Read the module active DTC's. If the module reports NO ACTIVE DTC's the defective component has been removed from the system and should be replaced. If the DTC is still active, continue this process until all components in the circuit have been tested. Then disconnect the module connector and connect the matching adapter to the module connector. With all airbags disconnected and the adapter installed the squib wiring can be tested for open and shorted conditions.

DIAGNOSTIC TROUBLE CODES
Airbag diagnostic trouble codes consist of active and stored codes. If more than one code exists, diagnostic priority should be given to the active codes. Each diagnostic trouble code is diagnosed by following a specific testing procedure. The diagnostic test procedures contain step-by-step instructions for determining the cause of the trouble codes. It is not necessary to perform all of the tests in this book to diagnose an individual code. Always begin by reading the diagnostic trouble codes with the DRBIII(R). This will direct you to the specific test(s) that must be performed. In certain test procedures within this manual, diagnostic trouble codes are used as a diagnostic tool.

ACTIVE CODES
The code becomes active as soon as the malfunction is detected or key-on, whichever occurs first. An active trouble code indicates an on-going malfunction. This means that the defect is currently there every time the Occupant Restraint Controller checks that circuit or component. It is impossible to erase an active code. Active diagnostic trouble codes for the airbag system are not permanent and will change the moment the reason for the code is corrected. With the exception of the warning lamp trouble codes or malfunctions, when a malfunction is detected, the airbag lamp remains lit for a minimum of 12 seconds or as long as the malfunction is present.

STORED CODES
Airbag codes are automatically stored in the ORC's memory as soon as the malfunction is detected. A stored code indicates there was an active code present at some time. When a trouble code occurs, the Airbag Warning Indicator illuminates for 12 seconds minimum (even if the problem existed for less than 12 seconds). Once the code is no longer active, the time in minutes it was active, and the number of times the ignition has been cycled since the problem was last detected will be displayed. The minimum time shown for any code will be one minute, even if the code was actually present for less than one minute. Thus, the time shown for a code that was present for two minutes 13 seconds, for example, would be three minutes. If a malfunction is detected a diagnostic trouble code is stored and will remain stored. When and if the malfunction ceases to exist, an ignition cycle count will be initiated for that code. If the ignition cycle count reaches 100 without a reoccurrence of the same malfunction, the diagnostic trouble code is erased and that ignition cycle counter is reset to zero. The ignition cycle counter will be reset and diagnostic trouble code will continue to be a stored code, If the malfunction reoccurs before the count reaches 100. If a malfunction is not active while performing a diagnostic test procedure, the active code diagnostic test will not locate the source of the problem. In this case, the stored code can indicate an area to inspect. Maintain a safe distance from all airbags while performing the following inspection. If no obvious problems are found, erase stored codes, and with the ignition on wiggle the wire harness and connectors, rotate the steering wheel from stop to stop. Recheck for codes periodically as you work through the system. This procedure may uncover a malfunction that is difficult to locate.