Purge Valve Leak Test

The Purge Valve Leak Test runs only if there was a cold start this ignition and the Weak Vacuum Test - Stage 1 test did not fail. This test monitors the purge valve for leaks. During the test, both the vent and the purge valves close. If a vacuum develops, the purge valve is leaking and a DTC P0440 is reported.

The canister vent solenoid is used to seal the fuel system during the [1][2]EVAP Leak Diagnostic Tests. The fuel tank pressure sensor is used to monitor system pressure (vacuum) during the leak tests.

The PCM conducts several intrusive tests on the Evaporative Emissions System and separates faults into one of the following fault categories:

DTC P0440 - EVAP System: The PCM commands the vent solenoid closed and the purge solenoid to a fixed duty cycle while monitoring the fuel tank pressure sensor. If the system is not capable of creating a calibrated vacuum in the system within a specific amount of time, the PCM logs a pending fault flag and awaits the next test results. A warm test is done if the cold test fails. The warm test can only pass the diagnostic. A Pass will extinguish the Malfunction Indicator Lamp (MIL) immediately. P0440

DTC P0442 - EVAP System Small Leak Detected: After passing the Large Leak Diagnostic, the PCM commands the vent solenoid closed and the purge solenoid to a fixed duty cycle while monitoring the fuel tank pressure sensor. After a calibrated vacuum level is achieved and the system is failing, the PCM then turns off the normally closed purge solenoid, continues to hold the vent solenoid closed and monitors the decay of vacuum in the system. If the decay is greater than a calibrated amount within a specific amount of time, a P0442 will be stored and the Service Engine Soon (MIL) will be illuminated. P0442

DTC P0446 - [1][2]EVAP Vent Solenoid Valve Control System: The PCM commands the vent solenoid closed and the purge solenoid to a fixed duty cycle while monitoring the fuel tank pressure sensor. The PCM then releases the normally open vent solenoid and expects a rapid decay in system pressure. If the pressure decay is less than a calibrated value in a given amount of time, a P0446 will be stored and the Service Engine Soon (MIL) will be illuminated. The P0446 can also be set anytime the vent solenoid is being commanded Off (open) and the vacuum in the tank exceeds a calibrated value. P0446

DTC P1441 - [1][2]EVAP Flow During Non-Purge: The PCM commands the vent solenoid closed and the purge solenoid to a 0% duty cycle (no flow) while monitoring the fuel tank pressure sensor. The PCM expects system pressure to remain constant. However, if system pressure (vacuum) is greater than a calibrated amount within a specific time, a P1441 will be stored and the Service Engine Soon (MIL) will be illuminated. P1441