Conditions for Setting the DTC

WARNING: This page is about a different car, the 2018 Chevrolet Suburban 3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The EVAP system is not able to achieve or maintain a calibrated level of vacuum less than 2.74 kPa (11 in H20) before a calibrated amount of purge volume has passed through the system.
After setting the DTC for the first time, 2 L (0.5 gal) of fuel must be consumed before setting the DTC for the second time.
NOTE: The weak vacuum follow-up test and Driver Information Center message is disabled on capless fuel fill systems.
With a DTC P0455 detected a weak vacuum follow-up test (fuel cap replacement test) will run and passes if tank vacuum is less than 2.74 kPa (11 in H20). This test will run for a maximum of 21 min. This test runs until it passes.