System Operation: SRS

WARNING: This page is about a different car, the 2017 Lincoln Navigator and 2017 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.

The SRS is controlled by the RCM, which continually monitors various inputs. When these inputs indicate a frontal or side crash, the RCM may deploy some components, based upon the severity of the crash and the sensor inputs. Refer to the System Diagram - SRS to view the SRS inputs and outputs.

Although some deployable devices may not have activated for all occupants during a crash, it does not mean that something is wrong with the SRS.

The RCM performs a self-test of the complete SRS during each startup. During normal operation, the IPC illuminates the airbag warning indicator continuously for 6 seconds. If the SRS is free of faults, the airbag warning indicator turns off and remains off. If a SRS fault exists, the airbag warning indicator illuminates and remains illuminated for the rest of the ignition cycle. The RCM communicates to the IPC via the HS-CAN. The IPC illuminates the airbag warning indicator based on messaging from the RCM or if there is no communication between the RCM and IPC. In addition to the self-test at start up, the RCM continuously monitors all of its SRS components and circuitry for correct operation.

Airbag Second Stage Deployment Check

The driver and passenger front airbags each have 2 deployment stages. After an airbag deployment, it is possible that stage 1 has deployed and stage 2 has not. If a front airbag has deployed, the front airbag must be remotely deployed using the appropriate airbag disposal procedure. For information on driver airbag and/or passenger airbag remote deployment, refer to Pyrotechnic Device Disposal .

Air Bag Warning Indicator

The airbag warning indicator:

is located in the IPC and proves out by lighting for 6 seconds and then turning off.
flashes and/or illuminates based on the message the IPC receives from the RCM.
illuminates if the IPC does not receive a message from the RCM.

Event Notification Signal

The event notification feature provides other vehicle subsystems with information pertaining to restraint system deployment or fuel cutoff status. Signal communication between the RCM and FPDM allows the FPDM to initiate fuel cut-off to disable the fuel system in the event of a crash.

After the fuel system is disabled, the vehicle can be re-started after carrying out the following steps:

Turn the ignition OFF.
Turn the ignition ON.
Turn the ignition OFF.
Turn the ignition ON.

Secondary Air Bag Warning (Chime)

The secondary airbag warning chime is an audible chime located in and controlled by the IPC. If a fault is detected with the airbag warning indicator, a DTC is stored in memory of the IPC. Upon receiving the message from the RCM that a SRS fault has been detected, the IPC sounds the secondary airbag warning chime in a repeating series of 5 beeps.

SOS Post-Crash Alert System™

The SOS Post-Crash Alert System™ is a system that is controlled by the BCM but initiated by the RCM. When a deployment event occurs, the RCM sends a message on the HS-CAN to the BCM. The BCM flashes the turn signal lamps and intermittently sounds the horn until the feature is turned off. For additional information about the SOS Post-Crash Alert System™, refer to Multifunction Electronic Modules .