Canister Vent Restriction Test
WARNING: This page is about a different car, the 2008 Suzuki Swift +, 2008 Pontiac Wave, and 2008 Chevrolet Aveo. However, it is still accessible from the selected car via links, so may be relevant.
After the small leak test has passed, a vacuum is retained in the evaporative emission (EVAP) system. The control module tests for a restricted vent path by commanding the purge valve OFF closed and the vent valve OFF open. The fuel tank pressure (FTP) sensor is monitored for a decrease in EVAP system vacuum. If the vacuum does not decrease to near 0 inch H2O in a calibrated time, a DTC sets.