The vapor pressure of a liquid is the point at which equilibrium pressure is reached, in a closed container, between molecules leaving the liquid and going into the gaseous phase and molecules leaving the gaseous phase and entering the liquid phase.n explanation of vapor pressure. Vapor pressure is constant when there is an equilibrium of water molecules moving between the liquid phase and the gaseous phase, in a closed container.
When a potential problem is detected, a dashboard warning light called a malfunction indicator light (MIL) is illuminated to alert the driver. An OBD system detects a problem well before symptoms such as poor performance, high emissions or poor fuel economy are recognized by the driver.
This means OBD2 can be a valuable diagnostic tool even when no trouble code is stored and the Malfunction Indicator Light (MIL) on the instrument panel is not illuminated. Instead of guessing, you can simply do a little driving and let OBD2 complete a âdrive cycle,â sometimes called a âtrip.â.