The knock sensor is located under the intake manifold. If your truck does not have supercharge, the time guide calls for 4.2hrs to complete the job. If it is supercharged, 3.0hrs. This may not be a job you want to tackle at home if you're not mechanically inclined. Its very in depth.
Service and repair of the knock sensor requires removal of the intake manifold.
Here's the procedure to getting to the knock sensor:
Drain coolant by removing drain plugs from both sides of cylinder block.
Separate ASCD and accelerator control wire from intake manifold collector (VG33E only).
Remove intake manifold collector from engine (VG33E only).
Remove intake manifold from engine. The following parts should be disconnected to remove intake manifold.
You will need an Intake Manifold Gasket kit to complete the job correctly