Park/Neutral Position (PNP) Switch (A/T Models)
WARNING: This page is about a different car, the 1995 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.
On some models, park/neutral switch delivers an input signal to NSW terminal of Engine Control Module (ECM), indicating gear position. The ECM uses information to control engine idle and fuel injection system.