Restraints Control Module
The Restraints Control Module (RCM) is installed on top of the floor tunnel, under the floor console, and controls operation of the Supplementary Restraint System (SRS).
The main functions of the RCM include:
- Impact detection and recording.
- Airbags, pedestrian protection system and seatbelt pretensioners firing.
- Self test and system monitoring, with status indication via the airbag warning indicator, and non volatile storage of fault information.
- Supply of yaw rate and lateral acceleration data for the Anti-lock Brake System (ABS) control module.
The RCM determines which elements of the SRS are to be deployed by using 2 internal areas:
- Impact severity evaluation.
- Deployment handler.
Impact severity evaluation uses data from the RCM internal accelerometer, the front impact sensors and the seatbelt buckle switches. Based on this data, the RCM decides which level of airbag deployment is required and forwards the information to the second area, the deployment handler.
The deployment handler first evaluates the status of the seat position sensor(s), seatbelt buckle switches and, on North American Specification (NAS) vehicles, the occupant classification sensor system. The deployment handler makes the final decision about which restraints should be deployed.
Data from the side impact and impact pressure sensors is used by the RCM in conjunction with acceleration data from the RCM internal accelerometer to make a deployment decision. The RCM processes the acceleration data and, subject to an impact being of high enough severity, decides whether the side airbag and side air curtain should be deployed.
Yaw rate and lateral acceleration data for the ABS control module is derived from the internal accelerometer. The data is transmitted on the High Speed (HS) Controller Area Network (CAN) chassis systems bus.
The RCM performs an on board testing of the airbags, pedestrian protection system and pretensioner firing circuits, the warning indicator circuits and the RCM status. The RCM also stores the fault codes. The impact and pressure sensors perform basic self tests controlled by the RCM.
The RCM drives the airbag warning indicator via a HS CAN signal. If the warning indicator fails, a fault code is recorded and a warning tone is sounded in place of the indicator if a further fault occurs. In the event of an impact, the RCM records certain collision data which can be accessed via the diagnostic connector.
An acceleration sensor in the RCM provides confirmation of an impact to evaluate the activation of airbags and pretensioners, pedestrian protection system. A lateral acceleration sensor monitors the lateral attitude of the vehicle. Various firing strategies are employed by the RCM to make sure that during an accident only the appropriate airbags, pedestrian protection system and pretensioners are deployed. The deployment strategy also depends on the inputs from the seatbelt buckle switches and, dependent on market specifications, on occupant position detection.
An energy reserve in the RCM makes sure there is always a certain amount of electric energy available. The electric energy is available for the total time of 150 milliseconds if the power supply from the ignition circuit is disrupted during an impact. The stored energy is sufficient to produce deployment signals for the driver airbag, the passenger airbag and the seatbelt pretensioners.
When the ignition is switched on the RCM performs a self test and then performs cyclical monitoring of the system. If a fault is detected the RCM stores a related fault code and illuminates the airbag warning indicator. The faults can be retrieved by Jaguar Land Rover approved diagnostic equipment. If a fault that could cause a false fire signal is detected, the RCM disables the respective firing circuit, and keeps it disabled during a impact event.