Note. For circuit reference, see the appropriate WIRING DIAGRAMS article. For connector and terminal identification, see CONNECTOR IDENTIFICATION .
Circuit Description
Evaporative (EVAP) emission system includes the following components, fuel tank, EVAP vent solenoid, fuel tank pressure sensor, fuel pipes and hoses, fuel cap, EVAP lines, EVAP canister and EVAP purge solenoid.
A restricted or blocked EVAP vent path is detected by monitoring fuel tank pressure during normal operation (EVAP vent solenoid open, EVAP purge solenoid normal). With the EVAP vent solenoid open, vacuum level in the system should be very low, unless the vent path is blocked.
A blockage can caused by the following conditions
- Faulty EVAP vent solenoid (stuck closed).
- Plugged, kinked or pinched vent hose.
- Shorted EVAP vent solenoid driver circuit.
- Plugged evaporative canister.
An incorrect fuel tank pressure sensor signal is detected by monitoring fuel tank pressure when ignition is first turned on during a cold start. If fuel tank pressure signal is out of range, EVAP diagnostic will not be able to detect leaks. If any of the conditions described are present, DTC P0446 will set.