Vacuum Test at System Powerup

NOTE: This diagnostic test requires approximately 500 ms in order to run to completion. If the ignition switch is turned to the crank position too quickly, the diagnostic may not complete the test.

NOTE: The fuel level input is required because the vacuum sensor is not accurate if it is immersed in a fuel or a high amount of vapor which is generated with low fuel levels.

This test is conducted during a cold start (Engine Coolant Temperature (ECT) = Intake Air Temperature (IAT) ±5°C) with a fuel level that is less than 85% and greater than 15% and an engine that is not cranking. Given the correct conditions at the system powerup, the Control Module commands the vent valve open and the purge valve closed. The Fuel Tank Pressure Sensor should indicate no pressure or vacuum during these conditions. It a pressure or vacuum is indicated, the Evaporative Emissions System (EVAP) diagnostic is completed for that trip and a Diagnostic Trouble Code (DTC) P0446 is stored. If the conditions are not correct this sub-test is skipped for this trip.