EVAP System Leak Testing

Some 2021-2022 Encore and Trax models equipped with the 1.4L engine (RPO LE2) may have DTC P0442, (Evaporative Emission [EVAP] System Small Leak Detected) set in the ECM.

The DTC P0442 diagnostic tests the EVAP system for a small leak. When the ignition is turned off and the EVAP system is sealed, a change in the fuel tank vapor temperature occurs, resulting in a corresponding pressure change in the fuel tank vapor space, which is monitored by the control module using the fuel tank pressure (FTP) sensor. If there is a leak in the system, the amount of pressure change will be less than that of a sealed system.

If DTC P0442 is set, complete the diagnostics in the appropriate Service Information and perform the EVAP system leak testing as directed. A leak can occur from a stuck open purge valve or stuck open canister vent valve as well as due to an unsealed EVAP system, so it is important to verify that all purge lines are properly connected.

TIP: Some leaks will only be noticeable under pressure while others will only be noticeable under vacuum. It is recommended to test for leaks both ways. Refer to Bulletin #21-NA-124 for additional information.

If no issues can be isolated, replace the evaporative emission canister (Fig. 2) and verify proper operation.


Fig. 2


TIP: Purge solenoids (Fig. 3) and purge pumps returned for warranty part analysis have been tested with no problems found. Do not replace these parts unless diagnosis confirms a concern with the purge system components.


Fig. 3


– Thanks to Robert Halas


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