EVAP
The Evaporative Emissions Control (EVAP) function allows for control of a purge control solenoid, so that a controlled amount of vapour from the fuel tank can be supplied to the engine intake instead of venting harmful emissions into the atmosphere. The solenoid is controlled by a PMW duty signal.
Frequency - This sets the frequency of the signal to the EVAP Solenoid. Typically a very low frequency is used for EVAP solenoids, typically 2 to 20Hz, to allow fine control between closed and small flow amounts.