Evaporative Emissions

The evaporative emission (EVAP) system:

• Is equipped with an on-board refueling vapor recovery (ORVR) system.
• Prevents hydrocarbon emissions from reaching the atmosphere.
• Stores fuel vapors in the EVAP canister that are generated during vehicle refueling, vehicle operation or hot soak until they can be consumed by the engine.
• Routes the stored fuel vapors to the engine during engine operation.
• Is controlled by the powertrain control module (PCM) which uses various sensor inputs to calculate the desired amount of purge flow. The PCM regulates the purge flow, induced by the application of intake manifold vacuum, by varying the duty cycle applied to the EVAP canister purge valve.
• has an EVAP test port for test purposes.

The fuel vapors are routed:

• From the fuel tank through the fuel vapor control valve and fuel vapor vent valve.
• To the EVAP canister through a vapor line.
• To the engine when the EVAP canister purge valve is opened by the PCM.

The fuel tank pressure (FTP) sensor:

• monitors the pressure levels in the fuel tank.
• Communicates the pressure reading to the PCM during the OBD II leak test.
• Is permanently attached to the fuel vapor control valve tube assembly.

The evaporative emission canister assembly:

• Is located above the rear subframe.
• Contains activated carbon.
• Stores fuel vapors.

The fuel tank filler cap:

• Relieves system pressure above 17 kPa (68.24 inches H2O).
• Relieves system vacuum below 5.65 kPa (22.68 inches H2O).

The canister vent solenoid:

• Is normally open.
• Seals the EVAP system for the inspection and maintenance (I/M 240) test and OBDII leak and pressure tests.
• Is mounted on the EVAP canister bracket assembly.
• Is repaired as a separate item.

The evaporative emission (EVAP) canister purge valve:

• Is normally closed.
• Regulates purging of the EVAP canister.
• Is controlled by the PCM.
• Is located in the engine compartment on the LH strut tower.

The fuel vapor vent (FVV) valve:

• Is permanently mounted to the fuel tank.
• Prevents suspended liquid fuel from being drawn into the EVAP canister along with the fuel vapors.

The fuel vapor control valve:

• Is permanently mounted to the fuel tank.
• Controls fuel tank refueling fill level.
• Prevents suspended liquid fuel from being drawn into the EVAP canister along with the fuel vapors.
• Relieves system pressure above 14 kPa (56.21 inches H2O).

The underbody fuel supply and vapor tube assembly:

• Is located under the LH rocker panel.
• Includes both the fuel supply line and the EVAP canister purge outlet tube.
• Supplies fuel from the fuel pump to the fuel filter.
• Routes fuel vapors from the fuel vapor control valve tube assembly to the engine compartment fuel supply and vapor tube.
• Is repaired as an assembly.

The engine compartment fuel supply and vapor tube assembly:

• Is located on the LH side of the engine compartment.
• Supplies fuel from the fuel filter to the fuel injection supply manifold.
• Routes fuel vapors from the underbody fuel supply and vapor tube assembly to the EVAP canister purge valve.
• Is repaired as an assembly.

The evaporative emission (EVAP) system monitor:

• Is a self-test strategy within the PCM, which tests the integrity of the EVAP system.
• monitors the EVAP system for leaks.
• monitors electronic EVAP components for irrationally high or low voltages.
• monitors for correct EVAP system operation.
• Uses negative leak test method to test and activate the EVAP system.

The evaporative emission (EVAP) test port:

• Is used to connect the Evaporative Emission System Leak Tester to the EVAP system.
• Is located on the EVAP canister purge valve.

The EVAP Running Loss System Leak Test:

• Utilizes intake manifold vacuum to test the EVAP system and involves several stages.