Circuit Description

Following components are included in Evaporative (EVAP) system:

• Fuel tank.
• EVAP canister vent solenoid.
• Fuel tank (vapor) pressure sensor.
• Vapor lines.
• Fuel filler cap.
• EVAP emissions canister.
• Purge lines.
• EVAP canister purge solenoid.

EVAP leak detection diagnostic strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. PCM monitors vacuum level via Fuel Vapor Pressure (FVP) sensor input. At an appropriate time, EVAP canister purge valve and EVAP canister vent valve are turned ON, allowing engine vacuum to draw a small vacuum on entire EVAP system. After a desired vacuum level has been reached, EVAP canister purge valve is turned OFF, sealing system. A leak is detected by monitoring for a decrease in vacuum level over a given period of time, all other variables remaining constant. A small leak in system will cause DTC P0456 to set.