Electronic Frontal Sensor (EFS)
WARNING: This page is about a different car, the 2002 Pontiac Montana, 2002 Oldsmobile Silhouette, and 2002 Chevrolet Venture. However, it is still accessible from the selected car via links, so may be relevant.
EFS measure velocity changes to detect collisions which are severe enough to warrant air bag module deployment. When a frontal collision occurs, EFS will send signals to Sensing and Diagnostic Module (SDM) to assist in determining severity of collision. EFS is not part of deployment loop.