DTC P0442, P0455: EVAP Control System Leak Detected: Description

EVAP system includes a fuel pressure sensor and a Canister Vent Solenoid (CVS) valve. The system is capable of detecting holes in the fuel system down to 0.04" (1 mm).

ECM carries out test as follows:

• ECM closes the EVAP purge valve and CVS valve which closes off the fuel vapor storage system. The vent pressure will increase due to the fuel vapor pressure in the fuel tank. If the fuel vapor pressure increase is more than the acceptable limit, the test will abort because a false leak test response will result.
• Next, the purge valve is opened during engine idle allowing the fuel tank pressure to decrease due to purge operation.
• ECM will perform the leak test measurement. The pressure recorded from the tests determines the extent of a possible leak. If leak test measurement is greater than a preset limit on two consecutive tests, the ECM will set the appropriate DTC and illuminate the MIL. The leak test measurement is only carried out during engine idle with the vehicle stationary. When leak test is complete, ECM opens the CVS valve, returning the system to normal purge operation.