EMISSION CONTROL SYSTEM DETAILS


  1. FUNCTION OF MAIN COMPONENTS


    1. The main components of the emission control system are as follows:

      Component Function
      Exhaust Emission System ECM Determines an optimal fuel injection volume based on the signals from various sensors.
      TWC Reduces CO, HC and NOx in the exhaust gas.
      Oxygen Sensor Detects the oxygen concentration in the exhaust emissions by measuring the electromotive force generated in the sensor itself. For details, see the 2TR-FE Engine Control.
      Air Fuel Ratio Sensor*
      Air Injection System* Air Pump Uses a built-in DC motor to supply air to the air switching valve.
      Air Switching Valve Introduces air that is pumped by the air pump into the exhaust manifold.
      Air Injection Control Driver

      • Activated by the ECM, the air injection control driver actuates the electric air pump and the air switching valve.

      • Detects an input-output circuit failure at the air injection control driver and transmits it to the ECM.
      ECM

      • Controls the air injection system in accordance with signals from the crankshaft position sensor, engine coolant temperature sensor and intake mass air flow meter sub-assembly.

      • Receives a failure detection signal from the air injection control driver and stores a corresponding DTC in memory.
      Evaporative Emission Control ECM Sends signals to the VSV (for EVAP) to control the purge flow.
      Charcoal Canister Sub-assembly Contains activated charcoal to absorb the fuel vapor created in the fuel tank.
      VSV (for EVAP) 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 into the intake manifold.

      • *: Models compliant with EURO 4 emission regulations

  2. FUNCTION


    1. Air Injection System


      1. To ensure the proper warm-up performance of the Three-Way Catalytic converters (TWCs) after starting a cold engine, an air injection system is used.

      2. This system consists of an air pump, an air switching valve, and an air injection control driver.

      3. The ECM estimates the amount of air injected to the TWCs based on signals from the intake mass air flow meter sub-assembly in order to regulate the air injection time.

  3. CONSTRUCTION


    1. Three-Way Catalyst (TWC)


      1. 2 TWCs have been provided in the exhaust pipe.

      2. These TWCs improve exhaust emissions by optimizing the cell density and the wall thickness.

        A01J2TRE01
        Text in Illustration
        *1 TWC - -

    2. Air Pump


      1. An air pump consists of a DC motor, an impeller and an air filter.

      2. DC motor operation is controlled by the ECM via an air injection control driver. The motor supplies air into an air switching valve through the impeller.

        A01J2ORE01
        Text in Illustration
        *1 Impeller *2 DC Motor
        *a Air Pump Cross Section - -
        A01J2OA To Air Switching Valve A01J2L7 From Air Inlet

    3. Air Switching Valve


      1. An air switching valve consists of an valve that switches the air flow and a reed valve that restricts the exhaust flow to one direction.

      2. The valve is a solenoid valve that is actuated by the air injection control driver.

      3. When the air switching valve turns on, an air injection pipe, which is provided in the exhaust manifold, directs the air from the air pump to the exhaust port.

        A01J2TAE01
        Text in Illustration
        *1 Air Switching Valve *2 Air Injection Pipe
        *3 Exhaust Manifold *4 Valve
        *5 Reed Valve - -
        *a Air Switching Valve Cross Section - -
        A01J2OA From Air Pump A01J2L7 To Air Injection Pipe

  4. OPERATION


    1. Air Injection Control Driver


      1. The air injection control driver is a non-contact type relay that uses semiconductors. Activated by the ECM, this driver actuates the air pump and the air switching valve.

      2. The air injection control driver also detects failures in the input and output circuits at the air injection control driver and transmits the failure status to the ECM via duty cycle signals.

      3. For details of the control of the air injection control driver, see the following system chart:

        A01J2PAE03
        DI Terminal Output
        Condition AIRP AIRV Output (Duty Cycle Signal)
        Open circuit in line between AIDI and DI terminals. - - A01J2SFE01
        Failure in line between ECM terminals and air injection control driver. - - A01J2SFE01
        Output failure at air injection control driver. (Failure in air pump actuation circuit) - - A01J2U7E01
        Output failure at air injection control driver. (Failure in air switching valve actuation circuit) - - A01J2UWE01
        Overheat failure of air injection control driver. - - A01J2OJE01
        Normal On On A01J2RCE01
        Off Off A01J2V9E01
        On Off
        Off On

    2. Evaporative Emission Control System


      1. Based on the signals from various sensors, the ECM opens and closes the VSV (for EVAP). Thus, it controls the purge flow of evaporative emissions (HC) in the charcoal canister sub-assembly in accordance with the engine conditions.