Heres the sensor

The tube runs from under it to the front of the passenger side exhaust manifold.

A crowfoot wrench makes it a little easier to get the upper nut off. Once removed from the truck spray with Brakleen or similar stuff. A 3' piece of 0.95 square weedeater line works good as a snake to run throung to pipe. Repeat spraying and reaming with the weedeater line about 4 times and it usually gets it pretty good. Before reinstalling pressurize the tube to check for any small cracks.