SFI SYSTEM DETAILS


  1. FUNCTION OF MAIN COMPONENTS


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

      Component Outline Quantity Function
      ECM 32-bit CPU 1 The ECM optimally controls the SFI, ESA and ETCS-i to suit the operating conditions of the engine in accordance with the signals provided by the sensors.
      Intake Mass Air Flow Meter Sub-assembly Mass Air Flow Meter Hot-wire Type 1 This sensor has a built-in hot-wire to directly detect the intake air mass.
      Intake Air Temperature Sensor Thermistor Type 1 This sensor detects the intake air temperature by means of an internal thermistor (built into the intake mass air flow meter sub-assembly).
      E. F. I. Engine Coolant Temperature Sensor Thermistor Type 1 This sensor detects the engine coolant temperature by means of an internal thermistor.
      Crank Position Sensor [No. of Rotor Teeth] Pick-up Coil Type [36 - 2] 1 This sensor detects the engine speed and the crank angle.
      Camshaft Position Sensor [No. of Rotor Teeth] Pick-up Coil Type [3] 1 This sensor performs cylinder identification and detects the VVT angle.
      Accelerator Pedal Sensor Assembly Linear (Non-contact) Type 1 This sensor detects the amount of pedal effort applied to the accelerator pedal.
      Throttle Body with Motor Assembly Throttle Position Sensor Linear (Non-contact) Type 1 This sensor detects the throttle valve opening angle.
      Knock Control Sensor (Bank 1, Sensor 1) Built-in Piezoelectric Type (Non-resonant Type/Flat Type) 1 This sensor detects engine knocking indirectly from the vibration of the cylinder block caused by engine knocking.
      Air Fuel Ratio Sensor (Bank 1, Sensor 1) Heated Type (Planar Type) 1 As with the oxygen sensor, this sensor detects the oxygen concentration in the exhaust gas. However, it detects the oxygen concentration in the exhaust gas linearly.
      Oxygen Sensor Heated Type (Cup Type) 1 This sensor detects the oxygen concentration in the exhaust gas by measuring the electromotive force which is generated in the sensor itself.
      Fuel Injector Assembly 12-hole Type 4 The injector is an electromagnetically-operated nozzle which injects fuel in accordance with signals from the ECM.

  2. SYSTEM CONTROL


    1. The engine control system of the 1AZ-FE engine has the following features.

      System Outline
      Sequential Multiport Fuel Injection (SFI)

      • This is an L-type SFI system. It directly detects the intake air mass with a hot-wire type intake mass air flow meter sub-assembly.

      • The fuel injection system is a sequential multiport fuel injection system.

      • Fuel injection takes 2 forms:


        • Synchronous injection, which always takes place with the same timing in accordance with the basic injection duration and an additional correction based on the signals provided by the sensors.


        • Non-synchronous injection, which takes place at the time an injection request based on the signals provided by the sensors is detected, regardless of the crankshaft position.

      • Synchronous injection is further divided into grouped injection during a cold start, and independent injection after the engine is started.
      Electronic Spark Advance (ESA)

      • Ignition timing is determined by the ECM based on signals from various sensors. The ECM corrects ignition timing in response to engine knocking.

      • This system selects the optimal ignition timing in accordance with the signals received from the sensors and sends ignition (IGT) signals to the igniters.
      Electronic Throttle Control System-intelligent (ETCS-i) Optimally controls the opening angle of the throttle valve in accordance with the accelerator pedal input and the engine and vehicle operating conditions.
      Variable Valve Timing-intelligent (VVT-i) Controls the intake camshaft to the optimal valve timing in accordance with the engine operating conditions.
      Fuel Pump Control

      • Fuel pump operation is controlled by signals from the ECM.

      • The fuel pump is stopped when an SRS airbag is deployed in a frontal, side, or rear side collision.
      Air Conditioning Cut-off Control By controlling the compressor with pulley assembly in accordance with the engine operating conditions, drivability is maintained.
      Cooling Fan Control Radiator cooling fan operation is controlled by signals from the ECM based on the E. F. I. engine coolant temperature sensor signal and the operating condition of the air conditioning.
      Air Fuel Ratio Sensor and Oxygen Sensor Heater Control Maintains the temperature of the air fuel ratio sensor or oxygen sensor at an appropriate level to increase the ability of the sensor to accurately detect the concentration of oxygen.
      Evaporative Emission Control The ECM controls the purge flow of evaporative emissions (HC) from the canister in accordance with engine operating conditions.
      Engine Immobiliser Prohibits fuel delivery and ignition if an attempt is made to start the engine with an invalid key.
      Fail-safe When the ECM detects a malfunction, the ECM stops or controls the engine according to the data stored in memory.
      Diagnosis When the ECM detects a malfunction, the ECM records the malfunction and information that relates to the fault.
      Brake Override System Restricts the driving torque when both the accelerator and brake pedals are depressed. (For the Activation Conditions and Inspection Method, refer to the Repair Manual.)

  3. FUNCTION


    1. VVT-i System


      1. The Variable Valve Timing-intelligent (VVT-i) system is designed to control the intake camshaft within a range of 40° (of crankshaft angle) to provide valve timing that is optimally suited to the engine operating conditions. This improves torque in all the speed ranges as well as increasing fuel economy, and reducing exhaust emissions.

        A01FD0FE02
        Text in Illustration
        *1 Camshaft Timing Oil Control Valve Assembly *2 Camshaft Position Sensor
        *3 E. F. I. Engine Coolant Temperature Sensor *4 ECM
        *5 Crank Position Sensor *6 Intake Mass Air Flow Meter Sub-assembly
        *7 Throttle Position Sensor *8

        Combination Meter Assembly

        - Vehicle Speed Signal

      2. The VVT-i system delivers excellent benefits in the different operating conditions as shown in the table below.

        Operation State Objective Effect

        - During Idling

        - At Light Load

        		 A01FCVHE04 Eliminating overlap reduces blow back to the intake side.

        - Stabilized idling rpm

        - Better fuel economy
        At Medium Load A01FCTTE02 Increasing overlap increases internal EGR to reduce pumping losses.

        - Better fuel economy

        - Improved emission control
        In Low to Medium Speed Range with Heavy Load A01FD34E02 Advancing the intake valve closing timing allows for volumetric efficiency improvement. Improved torque in low to medium speed range
        In High Speed Range with Heavy Load A01FCVHE03 Retarding the intake valve closing timing allows for volumetric efficiency improvement. Improved output
        At Low Temperatures A01FCVHE04 Eliminating overlap prevents blow back to the intake side and stabilizes the idle speed at fast idle.

        - Stabilized fast idle speed

        - Better fuel economy

        - Starting the Engine

        - Stopping the Engine

        		 A01FCVHE04 Eliminating overlap reduces blow back to the intake side. Improved startability

    2. Fuel Pump Control


      1. The fuel pump is controlled by the ECM. Fuel pump control has a fuel cut control function. Fuel cut control stops the fuel pump when any of the SRS airbags has deployed.

    3. Cooling Fan Control System


      1. The cooling fan control system achieves an optimal fan speed in accordance with the engine coolant temperature, vehicle speed, engine speed, and air conditioning operating conditions.

  4. CONSTRUCTION


    1. Air Fuel Ratio Sensor and Oxygen Sensor


      1. A planar type air fuel ratio sensor and a cup type oxygen sensor are used. The basic construction of the oxygen sensor and the air fuel ratio sensor is the same. However, they are divided into the cup type and the planar type, according to the different types of heater construction used.

      2. The planar type air fuel ratio sensor uses alumina, which excels in heat conductivity and electrical insulation, to integrate a sensor element with a heater, thus improving the warm-up performance of the sensor.

      3. The cup type oxygen sensor contains a sensor element that surrounds a heater.

        A01FCMSE01
        Text in Illustration
        *1 Air Fuel Ratio Sensor (Planar Type) *2 Oxygen Sensor (Cup Type)
        *3 Platinum Electrode *4 Alumina
        *5 Sensor Element (Zirconia) *6 Atmosphere
        *7 Heater *8 Diffusion Resistance Layer

      4. As illustrated below, the conventional oxygen sensor is characterized by a sudden change in its output voltage at the threshold of the stoichiometric air fuel ratio (14.7:1). In contrast, the air fuel ratio sensor data is approximately proportionate to the existing air fuel ratio. The air fuel ratio sensor converts the oxygen density to current and sends it to the ECM. As a result, the detection precision of the air fuel ratio has been improved. The air fuel ratio sensor data can be viewed using the intelligent tester.

        A01FCSJE23

    2. Intake Mass Air Flow Meter Sub-assembly


      1. The intake mass air flow meter sub-assembly, which is a plug-in type, allows a portion of the intake air to flow through the detection area. By directly measuring the mass and the flow rate of the intake air, the detection precision is improved and the intake air resistance is reduced.

      2. This intake mass air flow meter sub-assembly has a built-in intake air temperature sensor.

        A01FCFPE01
        Text in Illustration
        *1 Platinum Hot-wire Element *2 Temperature Sensing Element
        *3 Intake Air Temperature Sensor - -

    3. Crank Position Sensor


      1. The No. 1 crankshaft position sensor plate (timing rotor) of the crankshaft consists of 34 teeth with 2 teeth missing. The crankshaft position sensor outputs a crankshaft rotation signal every 10°, and the change of the signal due to the missing teeth is used to determine top-dead-center.

        A01FD57E03

    4. Camshaft Position Sensor


      1. To detect the camshaft position, a timing rotor on the intake camshaft is used to generate 3 pulses for every 2 revolutions of the crankshaft.

        A01FD6BE01

    5. Knock Control Sensor (Flat Type)


      1. In a conventional knock control sensor (resonant type), a vibration plate is built into the sensor. This plate has the same resonance point as the knocking* frequency of the engine block. This sensor can only detect vibrations in this frequency band.

        *: The term "Knock" or "Knocking" is used in this case to describe either preignition or detonation of the air fuel mixture in the combustion chamber. This preignition or detonation refers to the air fuel mixture being ignited earlier than is advantageous. This use of "Knock" or "Knocking" is not primarily used to refer to a loud mechanical noise that may be produced by an engine. A flat type knock control sensor (non-resonant type) has the ability to detect vibration in a wider frequency band (from about 5 kHz to 15 kHz). It has the following features:


        • A flat type knock control sensor is installed to an engine by placing it over the stud bolt installed on the cylinder block sub-assembly. For this reason, a hole for the stud bolt exists in the center of the sensor.

        • In the sensor, a steel weight is located in the upper portion. An insulator is located between the weight and a piezoelectric element.

        • An open/short circuit detection resistor is integrated in the sensor.

      2. The engine knocking frequency will vary slightly depending on the engine speed. The flat type knock control sensor can detect vibration even when the engine knocking frequency changes. Due to the use of the flat type knock control sensor, the vibration detection ability is increased compared to a conventional type knock control sensor, and more precise ignition timing control is possible.

        A01FCP5E11

      3. An open/short circuit detection resistor is integrated in the sensor. When the ignition is ON, the open circuit detection resistor in the knock control sensor and the resistor in the ECM keep the voltage at terminal KNK1 constant. An Integrated Circuit (IC) in the ECM constantly monitors the voltage of terminal KNK1. If an open or short circuit occurs between the knock control sensor and the ECM, the voltage of terminal KNK1 will change and the ECM will detect this and store a Diagnostic Trouble Code (DTC).

        A01FCX4E20

      4. Vibrations caused by knocking are transmitted to the steel weight. The inertia of this weight applies pressure to the piezoelectric element. This action generates electromotive force.

        A01FCN5E01
        Text in Illustration
        *1 Steel Weight *2 Inertia
        *3 Piezoelectric Element - -

        Tech Tips

        To prevent water accumulation in the connector, make sure to install the flat type knock control sensor in the position as shown in the following illustration.

        A01FD78E01
        Text in Illustration
        *1 Knock Control Sensor - -

    6. Throttle Position Sensor


      1. This non-contact type throttle position sensor uses a Hall IC, which is mounted on the throttle body with motor assembly.


        • The Hall IC is surrounded by a magnetic yoke. The Hall IC converts the changes that occur in the magnetic flux into electrical signals, and outputs them in the form of throttle valve position signals to the ECM.

        • The Hall IC contains circuits for the main and sub signals. It converts the throttle valve opening angle into electric signals that have differing characteristics, and outputs them to the ECM.

          A01FCIYE01

          Tech Tips

          The inspection method differs from a contact type throttle position sensor because this non-contact type throttle position sensor uses a Hall IC. For details, refer to the Repair Manual.

    7. Accelerator Pedal Sensor Assembly


      1. This non-contact type accelerator pedal sensor assembly uses a Hall IC, which is mounted on the accelerator pedal arm.


        • A magnetic yoke is mounted at the base of the accelerator pedal arm. This yoke rotates around the Hall IC in accordance with the amount of effort that is applied to the accelerator pedal. The Hall IC converts the changes in the magnetic flux that occur into electrical signals, and outputs them in the form of accelerator pedal sensor signals to the ECM.

        • The Hall IC contains 2 circuits, 1 for the main signal, and 1 for the sub signal. It converts the accelerator pedal position (angle) into electric signals that have differing characteristics and outputs them to the ECM.

          A01FCO3E01

          Tech Tips

          The inspection method differs from a contact type accelerator pedal sensor assembly because this non-contact type accelerator pedal sensor assembly uses a Hall IC. For details, refer to the Repair Manual.

    8. Camshaft Timing Oil Control Valve Assembly


      1. The camshaft timing oil control valve assembly controls its spool valve using duty-cycle control from the ECM. This allows hydraulic pressure to be applied to the camshaft timing gear assembly advance or retard side. When the engine is stopped, the camshaft timing oil control valve assembly will move to the retard position.

        A01FCJSE02
        Text in Illustration
        *1 Spool Valve *2 Sleeve
        *3 Spring *4 Plunger
        *5 Coil - -
        *a To Camshaft Timing Gear Assembly (Advance Side) *b To Camshaft Timing Gear Assembly (Retard Side)
        *c Drain *d Oil Pressure

    9. Ignition Coil Assembly


      1. The Direct Ignition System (DIS) provides 4 ignition coil assemblies, 1 for each cylinder. The spark plug caps, which provide contact to the spark plugs, are integrated with the ignition coil assembly. Also, an igniter is enclosed to simplify the system.

        A01FCVCE01
        Text in Illustration
        *1 Igniter *2 Primary Coil
        *3 Iron Core *4 Secondary Coil
        *5 Plug Cap - -

    10. Spark Plug


      1. Iridium-tipped spark plugs are used to achieve a 100000 km (60000 miles) maintenance interval. By making the center electrode of iridium, it is possible to achieve superior ignition performance and durability when compared to platinum-tipped spark plugs.

        A01FCQ3E02
        Text in Illustration
        *1 Iridium Tip *2 Platinum Tip

  5. OPERATION


    1. VVT-i System


      1. Based on engine speed, intake air volume, throttle position and engine coolant temperature, the ECM calculates optimal valve timing for all driving conditions. The ECM also controls the camshaft timing oil control valve assembly. In addition, the ECM uses signals from the camshaft position sensor and the crank position sensor to detect the actual valve timing, thus providing feedback control to achieve the target valve timing.

        A01FD0QE01

      2. When the camshaft timing oil control valve assembly is positioned as illustrated below by the advance signals from the ECM, the resultant oil pressure is applied to the timing advance side vane chamber to rotate the camshaft in the timing advance direction.

        A01FD25E02
        Text in Illustration
        *1 Vane *2 ECM
        *a Rotation Direction *b Oil Pressure
        *c In *d Drain

      3. When the camshaft timing oil control valve assembly is positioned as illustrated below by the retard signals from the ECM, the resultant oil pressure is applied to the timing retard side vane chamber to rotate the camshaft in the timing retard direction.

        A01FCYKE01
        Text in Illustration
        *1 Vane *2 ECM
        *a Rotation Direction *b Oil Pressure
        *c Drain *d In

      4. After reaching the target timing, the engine valve timing is maintained by keeping the camshaft timing oil control valve assembly in the neutral position unless the engine operating conditions change. This maintains the engine valve timing at the desired target position by preventing the engine oil from running out of the camshaft timing oil control valve assembly.

    2. Fuel Pump Control


      1. The fuel pump is controlled by the ECM. Fuel pump control has a fuel cut control function. Fuel cut control stops the fuel pump when any of the SRS airbags has deployed.


        • When the ECM detects the airbag deployment signal from the airbag sensor assembly, the ECM will turn the circuit opening relay off. After fuel cut control has been activated, turning the ignition switch from off to ON cancels fuel cut control, and the engine can be restarted.

          A01FCWXE05

    3. Cooling Fan Control System


      1. For the cooling fan control system, the ECM controls the cooling fan speed in accordance with the engine coolant temperature and the air conditioning operating conditions.


        • The ECM controls the cooling fan speed based on air conditioning pressure sensor signals and engine coolant temperature sensor signals. The air conditioning pressure sensor signals are sent from the air conditioning amplifier to the ECM. This control is accomplished by operating the 2 fan motors in 2 stages, at low speed (series connection) and high speed (parallel connection).

        A01FCTZE01
        A01FCKOE01

  6. FAIL-SAFE


    1. When a malfunction of any of the sensors is detected, there is a possibility of an engine or other malfunction occurring if the ECM were to continue normal control. To prevent such a problem, the fail-safe function of the ECM either relies on the data stored in memory to allow the engine control system to continue operating, or stops the engine if a hazard is anticipated. For details, refer to the Repair Manual.

  7. DIAGNOSIS


    1. When the ECM detects a malfunction, the ECM records information related to the fault. Furthermore, the Malfunction Indicator Lamp (MIL) in the combination meter assembly illuminates to inform the driver.

    2. The ECM also stores Diagnostic Trouble Codes (DTCs) for malfunctions it has detected. The DTCs can be accessed by using an intelligent tester.

    3. For details, refer to the Repair Manual.