Hi sir
First test the sensor, very easy, use the Camera of his cell, since the Sensor are I.R you can NOT see it , with his eyes.
The camera cell, is building for to detect , this kind of Ligh I.R if you see in his camera, some Blue light ON, the sensor is ok, otherwise is faulty. and replace. However clean it, with special electronic spray. and see if the cables of sensor is o.k , and NOT oil, grease, is there.
If everything is o.k, measure the voltage ( power supply , according with his schematic electrical diagrams) to the sensor .