Deployment Handler

The deployment handler evaluates the status of the seatbelt buckle switches, driver seat position sensor and, where fitted, the passenger seat position sensor and passenger seat occupant detection or classification system, are examined before a decision is made about which restraints should 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 airbag module and air curtain should be deployed.

On board testing of the airbag modules, front seatbelt pretensioner firing circuits, warning indicator circuits and module status is performed by the RCM together with the storing of Diagnostic Trouble Code (DTC)s. The impact and pressure sensors perform basic self-tests.

The RCM drives the airbag warning indicator on the Instrument Cluster (IC) via a HS CAN powertrain systems bus signal. If the warning indicator fails, a DTC is recorded and a warning tone is sounded in place of the indicator if a further fault occurs. The RCM also provides a temporary back-up power supply to operate the airbag 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 airbag and pretensioner activation is necessary. Various firing strategies are employed by the RCM to ensure that during an accident only the appropriate airbags and pretensioners are fired. The firing strategy used also depends on the inputs from the seatbelt buckle switches 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 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 DTC and illuminates the airbag warning indicator. The faults can be retrieved by Jaguar approved diagnostic equipment over the HS CAN powertrain systems 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.