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 evaporative emission (EVAP) canister that are generated during vehicle operation or hot soak, or vehicle refueling, 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 evaporative emission test port for test purposes.
The fuel vapors are routed:
- from the fuel tank through the fuel vapor vent valve and fuel vapor valve tube.
- 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 OBDII leak test.
- is located in the fuel tank and is repaired as a separate item.
The evaporative emission canister:
- is located under the rear of the vehicle near the fuel tank.
- contains activated carbon.
- stores fuel vapor.
The fuel tank filler cap:
- relieves system pressure above 14 kPa (56.21 inches H2O) .
- relieves system vacuum below 3.8 kPa (15.26 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 to the evaporative emission canister.
- 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.
The fuel vapor control valve tube assembly:
- consists of the fuel vapor control valve and fuel vapor vent valve.
- prevents suspended liquid fuel from being drawn into the evaporative emission canister along with the fuel vapors.
- returns the liquid to the fuel tank.
- includes a fresh air transfer tube routing fresh air between the canister vent solenoid hose and the fuel tank filler pipe assembly.
- requires two grommets to seal the fuel vapor control valve and fuel vapor vent valve to the fuel tank.
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 outlet tube near the EVAP canister purge valve.
The liquid/vapor fuel discriminator assembly:
- prevents liquid fuel suspended in the fuel vapor from being drawn into the evaporative emission canister along with the fuel vapors.
- returns the liquid to the tank.
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 and positive leak test methods to test and activate the EVAP system.
The EVAP Running Loss System Leak Test:
- utilizes intake manifold vacuum to test the EVAP system and involves several stages.