Circuit Description

The Evaporative Emissions (EVAP) system, as defined by federal regulation, includes the following components: fuel tank, EVAP vent solenoid, 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. EVAP system leak detection diagnostic strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. PCM monitors vacuum level using fuel tank pressure sensor input. At an appropriate time, EVAP canister purge valve and EVAP vent solenoid are turned on, allowing engine vacuum to draw a small vacuum on entire EVAP system.

DTC will set when fuel tank pressure change indicates EVAP system purge accumulation time is greater than 360 seconds. Diagnostic may take up to 20 minutes to run.