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Home >> BMW >> 1996 >> 318is Automatic >> Repair and Diagnosis >> Restraints >> Restraints Control Systems >> Passive Safety Systems - Overview >> Passive Safety Systems >> Multiple Restraint System (MRS & MRS II) >> Components >> Side Impact Sensors

Side Impact Sensors

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.

Fig 1: Identifying Side Impact Sensors
G03403428Courtesy of BMW OF NORTH AMERICA, INC.

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.

Fig 2: Identifying Internal Crash Sensor Circuit Diagram
G03403429Courtesy of BMW OF NORTH AMERICA, INC.