Inertia Fuel Shutoff (IFS) Switch
WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, 2012 Ford F450 Super Duty, and 2012 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The purpose of the IFS switch is to shut off the fuel pump if a collision occurs. It is located in the right hand side of the instrument panel and consists of a steel ball held in place by a magnet. When an impact occurs, the ball breaks loose from the magnet, rolls up a conical ramp and strikes a target plate opening the electrical contacts of the switch and turning off the electric fuel pump in the fuel conditioning module. Once the switch is open, it must be manually reset before restarting the vehicle. To reset the IFS switch, push the button on top of the switch down.