Side Impact Sensors
WARNING: This page does not describe the selected car, but rather 151 other vehicles, including the 2006 BMW X5, 2006 BMW M3, 2006 BMW 330Ci, 2006 BMW 325Ci, and 2005 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Electronic (piezoelectric) sensors are used for side impact detection. They are mounted at the left and right footwell cross members in front of the driver's and passenger's front seats. The sensors produce a pulse width modulated input signal to the MRS control module for side impact detection. The pulse width of the signal decreases in proportion to the severity of the impact.
The control module uses the internal crash sensor as a plausibility check for deployment of the side impact and ITS airbags. Both sensors must detect that the trigger threshold has been exceeded before the bags will deploy.