Part 2
PRINCIPLES OF OPERATIONSelf Test/On-Demand
The on-demand Self Test option is used to verify that no electrical concerns exist with the air bag supplemental restraint system (SRS). Upon entering the self-test, the restraints control module (RCM) and the occupant classification sensor (OCS) module will make an electrical check of each electrical component in the system. If a concern is detected, a DTC is displayed on the scan tool with a brief description of the diagnostic trouble code (DTC). The self-test should always be carried out after any repair to verify that the repair was successful.
To run the on-demand Self Test, follow these steps:
1. Connect the scan tool to the data link connector (DLC).
2. Turn the ignition switch to the ON position.
3. Follow the manufacturer's instructions for the scan tool being used.
4. Select RCM or OCSM.
5. Select Self-Test.
6. The module will run the self-test and display on-demand (reflecting hard system concerns) and continuous memory (historic) DTCs on the scan tool.
Self Test/Continuous Memory and Clear DTCs
During vehicle operation, the restraints control module (RCM) and the occupant classification sensor (OCS) module will detect and store on-demand (reflecting hard system concerns) and continuous memory (historic) diagnostic trouble codes (DTCs). The DTC strategy employed by the RCM incorporates a time-out scheme for determining when a concern exists in the system. This requires a concern may exist for up to one minute in the system before the RCM will detect it. For the RCM to determine that a concern no longer exists, the concern must be absent for up to one minute. The actual detection time-outs vary with each DTC. DTCs can be retrieved with a scan tool using the Self Test option. All DTCs stored in the RCM and OCS module will be displayed on the scan tool along with a brief description of the DTC. If no DTCs are present, the scan tool will display a SYSTEM PASSED message. This option can also be used to clear DTCs from the RCM and OCS module memory, as long as the concern no longer exists.
Once 75 hours of operation have been recorded by the RCM/OCS module since the concern was last detected, all continuous memory DTCs will automatically be removed from memory.
To retrieve or clear DTCs, follow these steps:
1. Connect the scan tool to the data link connector (DLC).
2. Turn the ignition switch to the ON position.
3. Follow the manufacturer's instructions for the scan tool being used.
4. Select RCM or OCSM.
5. Select Self Test.
6. NOTE: Before proceeding with the clearing operation, make note of the diagnostic trouble codes (DTCs) displayed. Once cleared, continuous DTCs cannot be retrieved.
All DTCs will be displayed on the screen.
7. Clear the DTCs. After clearing the DTCs, cycle the ignition OFF, then ON.
- Continuous memory DTCs that have been cleared will not reoccur as "continuous memory" in the same key cycle. Only new DTCs which were not present before clearing can occur as "continuous memory" after clearing.
Occupant Classification System (OCS) Zero Seat Weight Test
The Zero Seat Weight Test verifies the OCS system measures zero weight for an empty seat. It is necessary to carry out the Zero Seat Weight Test any time the front passenger seat is serviced or removed from the vehicle or as directed in the procedures. Refer to Zero Seat Weight Test.
Occupant Classification System (OCS) System Reset
The System Reset active command resets the zero point of the occupant classification sensor (OCS) system.
The System Reset active command should only be carried out if a new OCS component is installed or as directed.
DataLogger PID/Data
The DataLogger PID/Data option allows the scan tool operator to read the state of several parameter IDs (PIDs) to aid in diagnosing the system. PIDs are real time measurements of parameters, such as voltages and resistances, calculated by the restraints control module (RCM) or the occupant classification sensor (OCS) module and sent to the scan tool for display. Many of the PIDs supported by the modules are calculated periodically and are, therefore, not true real time readings.
To retrieve PIDs, follow these steps:
1. Connect the scan tool to the data link connector (DLC).
2. Turn the ignition switch to the ON position.
3. Follow the manufacturer's instructions for the scan tool being used.
4. Select RCM or OCSM.
5. Select DataLogger.
Active Commands
System Reset
System Reset active command sets the zero set point or rezeros the occupant classification sensor (OCS) system. Refer to Occupant Classification Sensor (OCS) System Reset. Programming and Relearning
Zero Seat Weight Test
The Zero Seat Weight Test verifies the OCS system measures zero weight for an empty seat. Refer to Occupant Classification Sensor (OCS) System Zero Seat Weight Test. Component Tests and General Diagnostics
Instrument Cluster Module
These commands allow the technician to verify the operation of instrument cluster module components and subsystems.
Lamp Fault Codes
This vehicle supports lamp fault codes (LFCs) only when the restraints control module (RCM) is in plant mode. A new RCM installed to a vehicle will be in plant mode until:
- programmable module installation (PMI) has been carried out.
- the RCM sees a fault-free supplemental restraint system (SRS) (no diagnostic trouble codes (DTCs) present).
If a LFC is present after completing PMI, a fault is present in the SRS and on-demand DTCs must be retrieved and diagnosed.
Diagnosing Customer Concerns With On-Demand Diagnostic Trouble Codes (DTCs)
NOTE: Most supplemental restraint system (SRS) diagnostic procedures will require depowering and repowering of the SRS. Depowering and repowering requires disconnecting of the battery and removal of the restraints control module (RCM) fuse. This reduces the risk of accidental deployment of SRS components while diagnostic procedures are being carried out.
If the air bag warning indicator is reported ON by the customer when the vehicle comes in for service, connect the scan tool and follow the Diagnostic Instruction procedures to identify the concern.
Once the diagnostic trouble code (DTC) is known, read the Normal Operation of the pinpoint test for the DTC involved.
Using the scan tool with the use of PIDs and active command(s) may be of assistance in diagnosing the concern.
- Follow the depowering procedure as directed.
- Determine the location of components involved in creating the DTC.
- Carry out a thorough visual inspection of:
- components.
- connectors.
- splices and wiring harnesses.
- insulation on conductors.
Diagnosing Customer Concerns With Continuous Memory Diagnostic Trouble Codes (DTCs)
If the air bag warning indicator was reported ON by the customer but is not present when the vehicle comes in for service, follow the Diagnostic Instruction procedures to identify the intermittent diagnostic trouble code (DTC).
Once the DTC is known, read the Normal Operation of the pinpoint test for the DTC involved.
- Follow the depowering procedure as directed.
- Determine the location of components involved in creating the DTC.
- Carry out a thorough visual inspection of:
- components.
- connectors.
- splices and wiring harnesses.
- insulation on conductors.
Refer to the Possible Causes of the pinpoint test for the DTC involved, which lists the common concerns that relate to the DTC. Concerns are listed according to priority. Pinpoint Tests
Bit-Mapped Diagnostic Trouble Codes (DTCs)
Many of the continuous memory and on-demand diagnostic trouble codes (DTCs) that can be present in the restraints control module (RCM)/ occupant classification sensor (OCS) module provide general fault information and require accessing the associated bit-mapped parameter identification (PIDs) (fault PIDs) to identify the specific concern. DTCs that use fault PIDs are conceptually different from conventional DTCs.
Conventional DTCs identify a specific concern for a given component and point to a particular diagnostic path. In the diagnostic path, PIDs are sometimes used to determine the root cause.
DTCs that use fault PIDs do not identify the specific concern. The DTC identifies the component(s) or type of components in which the concern exists. The next level, fault PIDs, identifies the specific device and fault condition. Fault PIDs are available for both on-demand (active) and continuous memory (historic) DTCs. Those associated PIDs are an extension of the information provided by the DTC and are identified by the same DTC number. Using both DTC and the fault PID is necessary to define the specific fault present (in the same manner as normal DTCs do).
A scan tool must be used to view DTCs and their fault PIDs. Once a scan tool has retrieved a DTC, use the scan tool to view the fault PIDs. Viewing the fault PIDs must be carried out to identify the specific concern that is present. When the viewing of fault PIDs has been carried out, the scan tool can display the PIDs associated with that DTC, including the status or state that exists (on-demand DTC) or existed (continuous memory DTC). Refer to the manufacturer's instructions for the scan tool being used on how to view fault PIDs.
Prove Out Procedure
Turn the ignition switch from the OFF to the ON position and visually monitor the air bag warning indicator with all supplemental restraint system (SRS) components connected. The air bag warning indicator will light continuously for approximately 6 seconds and then turn off. If an SRS fault is present, the air bag warning indicator will:
- fail to light.
- remain lit continuously.
- flash.
The air bag warning indicator may not illuminate until approximately 30 seconds after the ignition switch has been turned from the OFF to the ON position. This is the time required for the restraints control module (RCM) to complete the testing of the SRS. If the air bag warning indicator is inoperative and an SRS fault exists, a chime will sound in a pattern of 5 sets of 5 beeps. If this occurs, the air bag warning indicator will need to be repaired before diagnosis can continue.
Air Bag Reconnect Checklist
The checklist below should be completed following diagnosis or repair of any air bag system concern:
- All in-seat harness connectors connected?
- All air bag modules connected?
- Occupant classification sensor (OCS) module connected?
- All OCS weight sensor bolts connected?
- Safety canopy modules connected?
- Safety belt pretensioner connectors connected?
- All sensors (front and side impact sensors) connected?
- Restraints control module (RCM) connected?
- RCM fuse installed?
- Battery connected?
Air Bag Module Second Stage Deployment Check
Because the driver and passenger front air bags each have 2 deployment stages, it is possible that Stage 1 has deployed and Stage 2 has not.
If a front air bag module has deployed, it is mandatory that the front air bag module be remotely deployed using the appropriate air bag disposal procedure to make sure the second stage has been deployed.
- For information on driver or passenger air bag module remote deployment, refer to Pyrotechnic Device Disposal. Service and Repair
Glossary
Disconnect the Component
Disconnect the component means to disconnect the component vehicle harness connector, not to remove the component. Do not reconnect a disconnected component unless instructed to do so.
Deactivate the System
Deactivate the system means to carry out a deactivation procedure.
Depower the System
Depower the system means to disconnect the battery and remove the restraints control module (RCM) fuse.
Deployment Loop
The deployment loop is made up of the RCM, deployable device, air bag(s), safety belt pretensioners (safety canopies, deployable steering columns, load limiting retractor, adaptive tether, adaptive vent, if equipped) and associated circuits.
Install a New Component
Install a new component means to remove the existing component and install a new authorized part obtained from Ford Customer Service Division.
Prove Out the System
Prove out the system means to turn the ignition switch from the OFF to the ON position and visually monitor the air bag warning indicator with all SRS components connected. The air bag warning indicator will light continuously for approximately 6 seconds and then turn off. If an SRS fault is present, the air bag warning indicator will either fail to light or remain lit continuously. The air bag warning indicator may not illuminate until approximately 30 seconds after the ignition switch has been turned from the OFF to the ON position. This is the time required for the RCM to complete the testing of the SRS. If the air bag warning indicator is inoperative and an SRS fault exists, a chime will sound in a pattern of 5 sets of 5 beeps. If this occurs, the air bag warning indicator will need to be repaired before diagnosis can continue.
Reactivate the System
Reactivate the system means to carry out the reactivation procedure.
Reconnect the System
Reconnect the system means to reconnect all system components. Refer to Air Bag System Reconnect Checklist.
Repower the System
Repower the system means, turn the ignition ON, install the RCM fuse and connect the battery ground cable.
Secondary Air Bag Warning
The secondary air bag warning is an audible fault format that consists of 5 sets of 5 tone bursts, with each set of 5 tone bursts separated by a 5-second quiet period. One tone burst cycle will consist of one-second ON and one-second OFF. This series of 5 activations is repeated every 30 minutes.
Squib
A squib (igniter) is a device designed to convert electrical energy to the heat energy necessary to deploy a pyrotechnic restraints system device.
Verify the System
Verify the system means to prove out the system with restraint system components in place.