I dont know what sensors are on these cars but i install after market parking sensors.
But check the sensors make sure they are sitting in there mounts properly, all flush. as if the centre dot is touching the sides of the housing it with not work and will indicate that something is to close.
Also check there is no mud or dirt on them or in-between them and the mount.
On all the sensors i have worked on the sensor (the center Round bit), clicks into a housing that pushes into the bumper. Some cars with factory sensors only have a sensor and the clicks into the bumper itself so does not have the surround but, but being flush and clean still counts.