Circuit/System Description

This DTC tests for proper intake manifold vacuum flow to the evaporative emission (EVAP) system. The engine control module (ECM) opens the EVAP canister purge solenoid valve and closes the EVAP canister vent solenoid valve. The control module then monitors the fuel tank pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is less than a predetermined value within a predetermined time, this DTC sets.

The diagnostic is executed, once per trip, when the engine is running with purge enabled. There is a time delay after purge is enabled before this diagnostic can start. The time delay depends on whether the FTP sensor indicates pressure or vacuum. The initial state of the vent solenoid will be closed if there is still pressure in the tank after the time delay. The initial state of the vent solenoid will be open if there is vacuum in the tank.

When the commanded purge duty cycle is above a threshold, the EVAP leak detection pump switching valve transitions from vent to not venting position to prepare to create a vacuum. The EVAP leak detection pump pressure sensor, absolute, is monitored and compared to the initial value after the EVAP leak detection pump switching valve transitions from vent to not venting position and the vent solenoid is opened. The EVAP leak detection pump pressure sensor, absolute, must have a vacuum increase within a time period to indicate purge flow and pass the DTC P0497. Otherwise, P0497 fails.

After the diagnostic reports a decision, there is a time period to allow the vacuum in the fuel tank to bleed down before completing the diagnostic. This is to prevent the fuel tank protection logic from executing.