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 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 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 RCM together with the storing of fault codes.

The RCM drives the SRS warning indicator on the instrument pack via a CAN (controller area network) 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 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 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 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 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 air bag warning indicator. The faults can be retrieved by a Jaguar approved diagnostic system over the high speed CAN bus. 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 crash event