Fuel Vapor Build Pressure Test
WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
This test is used to determine the vacuum leak size. When the vacuum has decayed to near zero, the PCM subtracts measured slope from the vacuum decay to calculate to predict leak size. If the calculation indicates that a leak is present, the small leak test will fail.