Knock Sensor: Description
WARNING: This page is about a different car, the 2006 Chrysler Crossfire. However, it is still accessible from the selected car via links, so may be relevant.
Courtesy of DAIMLERCHRYSLER CORP.
The 3.2L engine is equipped with two knock sensors. The knock sensors bolt onto the cylinder block below the intake manifold in the engine valley. They are designed to detect engine vibration that is caused by detonation.