Firing Strategies

The seatbelt pretensioners are fired when the pretensioner impact limit is exceeded. The RCM only fires the pretensioners if the related seatbelt is fastened.

The driver and passenger airbags are only fired in a frontal impact. If an impact exceeds a stage 1 limit, but is less than the corresponding stage 2 limit, only one inflator in each airbag is fired (stage 2 is still fired, for airbag disposal purposes, after a delay of 100 ms). If an impact exceeds the stage 2 limit, the two inflators in each airbag are fired simultaneously. When the driver seat is forward of the seat position sensor switching point, the RCM introduces a time delay between firing the two inflators of the driver airbag.

The stage 2 inflator of the driver airbag is disabled if the driver seat is forward of the switching point of the seat position sensor.

If there is a fault with a seatbelt buckle switch, the RCM assumes the related seatbelt is fastened for the pretensioner firing strategy and unfastened for the driver and passenger airbag firing strategies. If there is a fault with the occupant classification sensor, the RCM disables the passenger airbag. If there is a fault with the passenger airbag deactivation switch, the RCM disables the passenger airbag.

If a side impact limit is exceeded, the RCM fires the side airbag and the side head airbag on that side of the vehicle. If the side impact limit on the front passenger side of the vehicle is exceeded, the RCM also evaluates the input from the occupant classification sensor, and fires the side airbag only if the front passenger seat is occupied by a large person (NAS only).

If multiple impacts occur during a crash event, after responding to the primary impact the RCM will output the appropriate fire signals in response to any further impacts if unfired units are available.

Front and Rear Impact Firing Strategy