EMISSION CONTROL SYSTEM DETAILS


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components of the 2GR-FE emission control system are as follows:

      Component Function
      TWC Oxidizes CO and HC in the exhaust gas and deoxidizes NOx at the same time, to purify them into CO2, H2O and N2.
      Air Fuel Ratio Sensor

      Is used to determine the concentration of oxygen remaining in the exhaust gas. Has a characteristic where its output is proportional to the engine air fuel ratio. Located upstream of the catalytic converter. For details Click here.
      Oxygen Sensor

      The signal of the air fuel ratio sensor changes abruptly between lean and rich at the stoichiometric air fuel ratio. Located downstream of the catalytic converter. For details Click here.
      ECM

      • Controls the volume of fuel consumed based primarily on the signal from the air fuel ratio sensor, with minor corrections based on the signal from the oxygen sensor. This control optimizes the exhaust emissions.

      • Controls the canister pump module and the purge VSV in accordance with the signals from various sensors, in order to achieve a purge volume that suits the driving conditions. In addition, the ECM monitors the system for any leak and stores a DTC if a malfunction is found.
      Charcoal Canister Assembly Contains activated charcoal to absorb the fuel vapor that is created in the fuel tank assembly.
      Fresh Air Line Fresh air goes into the charcoal canister assembly and the cleaned drain air goes out into the atmosphere.
      Canister Pump Module Vent Valve Opens and closes the fresh air line in accordance with signals from the ECM.
      Leak Detection Pump Applies vacuum to the evaporative emission system in accordance with signals from the ECM.
      Canister Pressure Sensor Detects the pressure in the evaporative emission system and sends the signals to the ECM.
      Purge VSV Opens in accordance with the signals from the ECM when the system is purging, in order to send the fuel vapor that was absorbed by the charcoal canister assembly into the intake manifold. In system monitoring mode, this valve controls the introduction of vacuum into the fuel tank assembly.
      Canister Filter Prevents dust and debris in the fresh air from entering the system.

  2. OPERATING CONDITION


    1. The following are the typical conditions necessary to enable an evaporative emission leak check:

      Typical Enabling Conditions

      • 5 hours have elapsed after the engine has been turned OFF*.

      • Altitude: Below 2400 m (8000 feet)

      • Battery Voltage: 10.5 V or more

      • Engine Switch: Off

      • Engine Coolant Temperature: 4.4 to 35°C (40 to 95°F)

      • Intake Air Temperature: 4.4 to 35°C (40 to 95°F)

      • *: If engine coolant temperature does not drop below 35°C (95°F), this time is extended to 7 hours. Even after that, if the temperature is not less than 35°C (95°F), the time is extended to 9.5 hours.

        Tech Tips

        The canister pump module performs a fuel evaporative emission leak check. This check is done approximately 5 hours after the engine is turned off. Sound may be heard coming from underneath the luggage compartment for several minutes. This does not indicate a malfunction. Pinpoint pressure test procedure is adopted by pressurizing the fresh air line that runs from the canister pump module to the air filler neck. For details, refer to the Repair Manual.

  3. SYSTEM CONTROL


    1. Purge Flow Control


      1. When the engine has reached a predetermined state (closed loop, engine coolant temperature above 80°C (176°F), etc.), stored fuel vapor is purged from the charcoal canister assembly whenever the purge VSV is opened by the ECM.

      2. The ECM will change the duty ratio cycle of the purge VSV, thus controlling purge flow volume. Purge flow volume is determined by intake manifold pressure and the duty ratio cycle of the purge VSV. Atmospheric pressure is allowed into the charcoal canister assembly to ensure that purge flow is constantly maintained whenever purge vacuum is applied to the charcoal canister assembly.

        A01HLTJE01

    2. Onboard Refueling Vapor Recovery (ORVR)


      1. When the internal pressure of the fuel tank assembly increases during refueling, the fuel vapor enters the charcoal canister assembly. The air that has had the fuel vapor removed from it will be discharged through the fresh air line. The vent valve is used to open and close the fresh air line, and it is always open (even when the engine is stopped) except when the vehicle is in monitoring mode (the valve will remain open as long as the vehicle is not in monitoring mode). If the vehicle is refueled in system monitoring mode, the ECM will recognize the refueling by way of the pressure sensor, which will detect the sudden pressure increase in the fuel tank assembly, and the ECM will open the vent valve.

        A01HLRXE01

    3. EVAP Leak Check


      1. The EVAP leak check operates in accordance with the following timing chart:

        A01HM8CE04
        Order Operation Description Time
        1) Atmospheric Pressure Measurement The ECM turns the vent valve off (vent) and measures EVAP system pressure to determine the atmospheric pressure. -
        2) 0.02 in. Leak Pressure Measurement The leak detection pump creates negative pressure (vacuum), limited by a 0.02 in. orifice and the pressure is measured. The ECM determines this as the 0.02 in. leak pressure (reference pressure). 20 sec.
        3) EVAP Leak Check The leak detection pump creates negative pressure (vacuum) in the EVAP system and the EVAP system pressure is measured. If the stabilized pressure is larger than the 0.02 in. leak pressure, ECM determines that the EVAP system has a leak. If the EVAP pressure does not stabilize within 15 minutes, the ECM cancels the EVAP monitor. Within 15 min.
        4) Purge VSV Monitor The ECM opens the purge VSV and measures the EVAP pressure increase. If the increase is large, the ECM interprets this as normal. 10 sec.
        5) Repeat 0.02 in. Leak Pressure Measurement The leak detection pump creates negative pressure (vacuum) limited by a 0.02 in. orifice and the pressure is measured. The ECM determines this as the 0.02 in. leak pressure. 20 sec.
        6) Final Check The ECM measures the atmospheric pressure and records the monitor result. -

  4. CONSTRUCTION


    1. Three-Way Catalytic Converter (TWC)


      1. TWCs are provided in the exhaust manifold sub-assembly of each bank and also in the front exhaust pipe assembly.

      2. An exhaust manifold with an integrated TWC is used for warm-up of the TWC in the front exhaust pipe assembly.

      3. An ultra thin-wall, high-cell density, ceramic type TWC is used for each exhaust manifold sub-assembly and a thin-wall, ceramic type TWC is used for the front exhaust pipe assembly.

      4. These TWCs enable improved exhaust emissions by optimizing the cell density and the wall thickness.

        A01HM0OE01
        Text in Illustration
        *1 Exhaust Manifold Sub-assembly RH (for Bank 1) *2 Exhaust Manifold Sub-assembly LH (for Bank 2)
        *3 TWC *4 Ultra Thin-wall
        *5 Front Exhaust Pipe Assembly - -

    2. Fuel Inlet (Fresh Air Inlet)


      1. The fresh air line inlet is located near the fuel inlet pipe opening. The fresh air from the atmosphere and drain air cleaned by the charcoal canister assembly will go in or out of the system through the passages shown below.

        A01HLXZE01
        Text in Illustration
        *1 Fuel Tank Cap *2 Fuel Inlet Pipe
        *3 Canister Filter *4 Cleaned Drain Air
        *a to Charcoal Canister Assembly - -
        A01HM7O Fresh Air

    3. Canister Pump Module


      1. The canister pump module consists of the vent valve, reference orifice, canister pressure sensor, leak detection pump, and pump motor.

      2. The vent valve switches the passages in accordance with the signals received from the ECM.

      3. A DC type brushless motor is used for the pump motor.

      4. A vane type leak detection pump is used.

        A01HM6YE05

    4. Fuel Tank Cap Assembly


      1. ID mark A is printed on the fuel tank cap assembly.

        A01HM2GE01
        Text in Illustration
        *a ID Mark - -

        CAUTION:

        Make sure to use a fuel tank cap assembly that has the same ID mark, or a malfunction may occur in the fuel system.

  5. OPERATION


    1. Atmospheric Pressure Measurement


      1. When the engine switch is turned off, the purge VSV and the vent valve are turned off. Therefore, atmospheric pressure is introduced into the charcoal canister assembly.

      2. The ECM measures the atmospheric pressure using the canister pressure sensor.

      3. If the measured atmospheric pressure is out of range, the ECM actuates the leak detection pump in order to monitor the changes in the pressure.

        A01HLW3E02

    2. 0.02 in. Leak Pressure Measurement


      1. The vent valve remains off, and the ECM introduces atmospheric pressure into the canister and actuates the leak detection pump in order to create a negative pressure.

      2. At this time, the pressure will not decrease beyond a 0.02 in. pressure due to the atmospheric pressure that enters through a 0.02 in. diameter reference orifice.

      3. The ECM compares the logic value and this pressure, and stores it as a 0.02 in. leak pressure in its memory.

      4. If the measurement value is below the standard, the ECM will determine that the reference orifice is clogged and store Diagnostic Trouble Code (DTC) P043E in its memory.

      5. If the measurement value is above the standard, the ECM will determine that a high flow rate pressure is passing through the reference orifice and store Diagnostic Trouble Code (DTC) P043F, P2401 and P2402 in its memory.

        A01HLPME02

    3. EVAP Leak Check


      1. While actuating the leak detection pump, the ECM turns the vent valve on in order to introduce a vacuum into the charcoal canister assembly.

      2. When the pressure in the system stabilizes, the ECM compares this pressure and the 0.02 in. pressure in order to check for a leakage.

      3. If the detection value is below the 0.02 in. pressure, the ECM determines that there is no leakage.

      4. If the detection value is above the 0.02 in. pressure and near atmospheric pressure, the ECM determines that there is a gross leakage (large hole).

      5. If the detection value is above the 0.02 in. pressure, the ECM determines that there is a small leakage.

        A01HLQJE02

    4. Purge VSV Monitor


      1. After completing an EVAP leak check, the ECM turns ON (open) the purge VSV with the leak detection pump actuated, and introduces the atmospheric pressure from the intake manifold to the charcoal canister assembly.

      2. If the pressure change at this time is within the normal range, the ECM determines the condition to be normal.

      3. If the pressure is out of the normal range, the ECM will stop the purge VSV monitor and store DTC P0441 in its memory.

        A01HLSSE02

    5. Repeat 0.02 in. Leak Pressure Measurement


      1. While the ECM operates the leak detection pump, the purge VSV and vent valve turns off and a repeat 0.02 in. leak pressure measurement is performed.

      2. The ECM compares the measured pressure with the pressure during EVAP leak check.

      3. If the pressure during the EVAP leak check is below the measured value, the ECM determines that there is no leakage.

      4. If the pressure during the EVAP leak check is above the 0.02 in. pressure and near atmospheric pressure, the ECM determines that there is a gross leakage (large hole) and stores DTC P0455 in its memory.

      5. If the pressure during the EVAP leak check is above the 0.02 in. pressure, the ECM determines that there is a small leakage and stores DTC P0456 in its memory.

        A01HLZIE03