Circuit Description

The DTC P0455 Evaporative Emission (EVAP) System Leak Detected diagnostic monitors the operation of the EVAP system. The EVAP control system leak detection diagnostic strategy is based on applying vacuum to the EVAP system, sealing the system, and then monitoring vacuum decay. The Powertrain Control Module (PCM) monitors the vacuum level via the Fuel Tank Pressure (FTP) sensor input. The PCM opens the EVAP canister purge valve and closes the EVAP vent valve, allowing the engine manifold pressure to draw a small vacuum on the entire EVAP system. If the difference between the minimum and maximum FTP sensor pressures are below a specified value, a DTC P0455 sets. The EVAP system used with this powertrain is part of an On-Board Refueling Vapor Recovery (ORVR) fuel system.

The EVAP system as defined by federal regulation includes the following components: fuel tank, EVAP canister vent valve, fuel tank pressure sensor, fuel pipes and hoses, vapor lines, fuel filler cap, fuel tank pressure control valve, EVAP canister, purge lines and EVAP canister purge valve.