Conditions For Setting the DTC

WARNING: This page is about a different car, the 2007 Isuzu i-370, 2007 GMC Canyon, and 2007 Chevrolet Colorado. 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 vacuum during the diagnostic test.
The DTC P0455 diagnostic runs up to 17 minutes from start-up.