LX FOCUS 2007 Rear Parking Sensors

[Rygor]

Anyone got any tips on troubleshooting the rear parking sensors on a 2007 Focus? When you throw it into reverse, you just get a constant tone like when you are too close to something. The sensors are clean, the connections looked tight to the 4 sensors behind the bumper.
Anyone got any pictures on how to unclip the sensor? Could only see it from looking under the bumper and was trying to avoid having to figure out how to remove the bumper if I could.