Diesel Pressure Sensor Testing Amazon Printed Books https://www.createspace.com/3786463 Amazon Kindle Edition http://www.amazon.com/Diesel-Common-I... Android APPs https://play.google.com/store/apps/de..... Explains how to test the diesel injection fuel pressure sensor. This is 3 wire sensor, with reference, signal and ground. Common rail Diesel fuel injection is now the state of the art in engine injection. The Bosch Piezoelectric (crystal) injector operates using a crystal stack, usually Quartz, that changes size when energized. The piezoelectric effect states that when a crystal such a Quarts is squeezed an electric current is generated. By the same token, when electricity is applied to the crystal is changes shape. This minute change in crystal size is used to trigger a small fuel chamber on and off. In turn, this chamber creates a pressure differential at the top of the injector which make it open and close. See further information here.