System Description

The DTC P0456 Evaporative Emission (EVAP) System Very Small Leak Detected diagnostic detects EVAP system leaks as small as 0.51 mm (0.02 in). The diagnostic strategy for the EVAP system uses a vacuum pump to test for system leaks, after the engine is OFF. A unique fuel tank, EVAP canister, and EVAP vacuum leak pump work together to provide enhanced system diagnosis. The vacuum leak pump, the fuel tank pressure (FTP) sensor, and the EVAP canister vent valve are all integral parts of one assembly. The assembly is attached directly to the EVAP canister, located near the fuel tank.

After the vehicle has sat with the engine OFF for at least 5 hours and the engine coolant temperature is less than 35°C (95°F), a comprehensive diagnostic is enabled. The complete diagnostic test can take up to 15 minutes to run, with leak detection comprising the largest portion of the test. Once the large leak test DTC P0455 passes, the powertrain control module (PCM) will continue to monitor the FTP sensor signal in order to determine if there is small leak. If a specified minimum value is not achieved or the minimum value can not be maintained, a DTC P0456 will set. For more detailed information on the EVAP system components and diagnostic strategy, refer to Evaporative Emission Control System Description .