Circuit Description
WARNING: This page is about a different car, the 2003 Toyota Camry. However, it is still accessible from the selected car via links, so may be relevant.
The neutral start switch goes on when the shift lever is in the N or P shift position. When it goes on, terminal NSW of the engine control module (ECM) is grounded to the body ground via the starter relay, thus the terminal NSW voltage becomes 0 V. When the shift lever is in the D, 2, L or R position, the park/neutral position switch goes off, so the voltage of the ECM. Terminal NSW becomes battery voltage and the voltage of the ECM internal power source. If the shift lever is moved from the N position to the D position, this signal is used for air-fuel ratio correction and for idle speed control (estimated control), etc.