Evaporative Emissions System: Description and Operation

The evaporative emissions system:
- prevents hydro carbon emissions from reaching the atmosphere.
- stores fuel vapors in the Evaporative Emissions canister (EVAP canister).
- returns the stored fuel vapors to the engine during engine operation.

Fuel vapors are routed:
- from the fuel tank through the two evaporative emission valves to the evaporative emissions canister through a vapor line.
- from there, to the engine when the evaporative emission canister purge valve (EVAP canister purge valve) is opened by the Powertrain Control Module (PCM).

The fuel tank pressure sensor:
- monitors the fuel tank pressure.
- Communicates the pressure readings to the powertrain control module during the OBD II leak test.

The fuel tank filler cap:
- relieves system pressure above 14 kPa (2 psi).
- relieves system vacuum below 3.8 kPa (0.53 psi).

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

The evaporative emission service vent valve:
- seals the evaporative emission system for the OBD II leak check.

The evaporative emissions canister:
- is located in front of the rear axle assembly.
- contains activated carbon.
- stores fuel vapors.