On an engine with emissions controls, the EVAP system stores fuel vapor from the tank and lets the engine burn it through a purge valve. The Fuel Tank Pressure Correction table lets NSP adjust EVAP control based on the pressure in the vapor line.
It only becomes active when a fuel tank pressure sensor is fitted and reporting on that line. Out of the box, every cell is zero, so it does nothing until you enter values. You can map it in one or two dimensions.
What to check first: that the sensor is set up correctly under EVAP wiring, and that it reads sensibly with the cap on and off. Then build corrections a little at a time, logging lambda during purge.
See the main EVAP article and the coolant temp correction. Need this screen? Ask us and we'll send it over with advice for your build.
