Additional Wiring
WARNING: This page is about a different car, the 2007 Chrysler PT Cruiser. However, it is still accessible from the selected car via links, so may be relevant.
For complete wiring diagrams, refer to SYSTEM WIRING DIAGRAMS article.
The theory behind the Natural Vacuum Leak Detection (NVLD) is adherence to the Ideal Gas Law. Pressure in a sealed vessel will change linearly as a function of the temperature of the gas in the vessel. Even small leaks will allow the pressure in the vessel to come to equilibrium with the atmospheric pressure. The General EVAP test runs by commanding purge flow during the leak size test and evaluates the NVLD vacuum switch.