Restraints Control Module
The restraints control module (RCM) is installed on the top of the transmission tunnel, in line with the B pillars, and controls operation of the supplemental restraint system (SRS). The main functions of the restraints control module (RCM) include:
- Crash detection and recording.
- Air bag and pretensioner firing.
- Self test and system monitoring, with status indication via the air bag warning indicator and non volatile storage of fault information.
The restraints control module (RCM) determines which elements of the supplemental restraint system (SRS) are to be deployed by using two internal areas:
Crash severity evaluation
This area evaluates crash severity by using data from the restraints control module (RCM) internal accelerometer, the front impact sensor and the safety belt sensors. Based on this data, the restraints control module (RCM) decides which level of air bag module deployment is required and forwards the information to the second area, the deployment handler.
Deployment handler
The status of the seat position sensor and safety belt sensors are examined before a decision is made about which restraints should finally be deployed.
Data from the side impact sensors is used by the restraints control module (RCM) in conjunction with acceleration data from the restraints control module (RCM) internal accelerometer to make a deployment decision. The restraints control module (RCM) processes the acceleration data and subject to an impact being of high enough severity, decides whether the side air bag module should be deployed.
On board testing of the air bag modules, safety belt pretensioner firing circuits, warning indicator circuits and module status (the front and side impact sensors perform basic self-tests) is performed by the restraints control module (RCM) together with the storing of fault codes.
The restraints control module (RCM) drives the supplemental restraint system (SRS) warning indicator on the instrument pack via a controller area network (CAN) signal. If the warning indicator fails, a fault code is recorded and a warning tone is sounded in place of the warning indicator if a further fault occurs. It also provides a temporary back-up power supply to operate the air bag modules in the event that, in crash conditions, the battery supply is lost. In the event of a crash, it records certain data which can be accessed via the diagnostic connector.
A safing sensor in the restraints control module (RCM) provides confirmation of an impact to verify if air bag and pretensioner activation is necessary. A roll over sensor monitors the lateral attitude of the vehicle. Various firing strategies are employed by the restraints control module (RCM) to ensure that during an accident only the appropriate air bags and pretensioners are fired. The firing strategy used also depends on the inputs from the safety belt sensors and the occupant monitoring system.
An energy reserve in the restraints control module (RCM) ensures there is always a minimum of 150 milliseconds of stored energy available if the power supply from the ignition switch is disrupted during a crash. The stored energy is sufficient to produce firing signals for the driver air bag, the passenger air bag and the safety belt pretensioners.
When the ignition is switched on the restraints control module (RCM) performs a self test and then performs cyclical monitoring of the system. If a fault is detected the restraints control module (RCM) stores a related fault code and illuminates the air bag warning indicator. The faults can be retrieved by a Jaguar approved diagnostic system over the high speed controller area network (CAN) bus. If a fault that could cause a false fire signal is detected, the restraints control module (RCM) disables the respective firing circuit, and keeps it disabled during a crash event