stand at the front of your truck...look between the a/c compressor and the Alternator. YOu will see a a gray boxy thing right between them thats it. It has a sensor with one wire coming out of it...this is oil pressure for your guage and a small hex plug...you can take that plug out and see where the oil level is. don't look to hard its right there...it is part of the timing gear cover and like i said it comes up between the a/c compressor and alternator...just make sure you take the black turbodiesel cover off the engine before you start looking...it will help you see things better
