Evaporative Emissions System: Description and Operation

The evaporative emission system:
- prevents hydrocarbon emissions from reaching the atmosphere.
- stores fuel vapors in the evaporative emissions canister.
- returns the stored fuel vapors to the engine during engine operation.
- has an evaporative emission test port for test purposes.

The fuel vapors are routed:
- from the fuel tank through the fuel vapor vent valve to the evaporative emissions canister.
- vapors are then routed through the fuel vapor control valve tube assembly to the evaporative emission canister.
- to the engine when the evaporative emission canister purge valve is opened by the Powertrain Control Module (PCM).

The fuel tank pressure sensor:
- monitors the pressure levels in the fuel tank.
- displays the pressure reading to the PCM during the OBDII Test.

The evaporative emissions canister:
- is located near the rear of the vehicle.
- contains activated carbon.
- stores fuel vapors.

The fuel tank filler cap:
- relieves system pressure above 13.7 kPa (2 psi).
- relieves system vacuum at 3.4 kpa (0.55 psi).

The canister vent solenoid:
- seals the evaporative emissions system for the OBDII Leak Test.
- is mounted to the evaporative emissions canister.
- is repaired as a separate item.

The evaporative emission canister purge valve:
- regulates purging of the evaporative emissions canister.
- is controlled by the powertrain control module.

The fuel vapor control valve tube assembly:
- prevents suspended liquid fuel with the fuel vapor from being drawn into the evaporative emission canister along with the fuel vapors.
- returns the liquid to the tank.