2024 Sierra Denali Evap Leak. The code p0442 indicates that the engine computer (pcm) has detected a small leak in the evap system. This is usually a straightforward fix with either the gas cap is bad and.

Symptoms of a p0455 include a lit check engine light as well as the. Code p0455 is typically triggered when your vehicle’s computer detects a large leak in the evap system.