Side impact airbag system for a vehicle includes a side airbag arranged to deploy along a left or right side of the vehicle and an electronic crash sensor. The electronic crash sensor includes a housing, a mass arranged within the housing to be movable in a lateral direction relative to the housing in response to lateral accelerations of the housing, and a control mechanism for controlling deployment of the side airbag and which is responsive to the motion of the mass only in the lateral direction. The housing is mounted in such a position and a direction as to sense an impact into a side of the vehicle resulting in lateral acceleration of the housing. The electronic crash sensor may generate a signal representative of the movement of the mass.