General
The engine control system consists of the following:
- 1. Various sensors, which detect the state of engine and driving conditions.
- 2. The engine control module (ECM), which controls various devices according to the signals from the sensors.
- 3. Various controlled devices.
Functionally, the engine control system is divided into the sub systems as follows:
• Fuel injection control system.
• Ignition control system.
• Throttle valve module system.
• Fuel pump control system.
• Radiator cooling fan control system.
• Evaporative emission control system.
• Exhaust gas recirculation (EGR) system (K10B and K12B up to MY 2010).
• A/F sensor heater control system.
• Oxygen sensor heater control system.
• A/C control system.
• Camshaft position control system (K12B as of MY 2011).
• Alternator control system (K12B as of MY 2011).
• Immobilizer control system.
• Controller (computer) communication system.
Throttle Valve Module Control System
The throttle valve module control system consists of the following:
• Throttle body assembly incorporating the throttle valve, throttle motor and throttle position (TP) sensors (main and sub).
• Accelerator pedal assembly incorporated with accelerator pedal position (APP) sensors (main and sub).
• Throttle motor control relay.
• ECM.
The ECM (5) detects the opening (depressed extent) of the accelerator pedal based on the signal voltage of the APP sensor (1). Using that data and the engine operation condition, the ECM calculates the optimum throttle valve opening. The ECM also detects the throttle valve opening based on the signal voltage of the TP sensor (3) and compares the opening with the calculated optimum throttle valve opening. When there is a difference, the ECM controls the duty ratio (100% – 0%) of the throttle motor control to drive the throttle motor (4). When there is no difference, the ECM controls the duty ratio of the throttle motor control to about 15% to maintain the throttle valve opening. In this way, the throttle valve (17) is opened and closed to achieve the optimum throttle valve opening.
The TP sensor and the APP sensor have two sensors (main and sub) each. When the ECM detects an abnormality in the system, the ECM turns off the throttle motor control relay (8) to stop controlling the throttle motor. When the throttle motor control relay is turned off, the throttle valve is fixed at a default opening from the completely closed position by the force of the return spring and open spring included in the throttle body. The default opening for K12B up to MY 2010 and K10B is 9°. The default opening for K12B as of MY 2011 is 7°.
The idle speed control is operated by the throttle motor, which opens and closes the throttle valve.
- 1. APP sensor
- 2. Throttle valve module assembly
- 3. TP sensor
- 4. Throttle motor
- 5. ECM
- 6. CPU
- 7. Drive circuit for throttle motor
- 8. Throttle motor control relay
- 9. From THR MOT fuse
- 10. From main relay
- 11. APP main signal
- 12. APP sub signal
- 13. TP main signal
- 14. TP sub signal
- 15. Drive signal to throttle motor
- 16. Power supply to throttle motor
- 17. Throttle valve
- 18. Control signal to throttle motor control relay
Throttle Valve Module System Calibration
The ECM calculates the throttle valve position on the basis of the completely closed throttle valve position data and the completely opened throttle valve position data. The completely closed and opened throttle valve position (signal voltage from TP sensor) differ one from the other due to the individual differences of the throttle valve, the TP sensor and the APP sensor. As such, individual differences must be taken into account for controlling the throttle valve; the ECM must be calibrated to the completely closed and opened throttle valve position data in the ECM.
Mixture Control Oxygen Sensor
The mixture control oxygen sensor is located at the cluster of the exhaust manifold (in front of the three way catalytic converter) and contains a sensor heater, a sensor element and an adjusting resistor.
The sensor element is a laminated construction, consisting of an IP cell, a detection chamber, a VS cell and a reference oxygen chamber. The IP cell and the VS cell each consists of a zirconia element. The ECM detects the oxygen concentration (air fuel ratio) of the exhaust emission from lean to rich in proportion by using the zirconia characteristic.
The sensor heater maintains the sensor element temperature at approximately 780 °C (1,436 °F) by the duty control signal so that the sensor element only activates at the specified temperature.
The adjusting resistor, installed in the sensor connector, compensates the individual difference in the output characteristic of the sensor element.
The VS cell generates the electromotive force depending on the oxygen concentration difference between the detection chamber and the oxygen reference chamber.
The ECM controls the intensity and the direction of the pump current to the IP cell so as to maintain the certain voltage between both electrodes of VS cell (between LFUN and LFVM terminals), therefore, the ECM maintains the oxygen concentration to a specified value in the detection chamber.
The ECM calculates the air and fuel ratio in the exhaust emission by the intensity and the direction of the pump current.
- 1. Mixture control oxygen sensor
- 2. Sensor heater
- 3. Sensor element
- 4. IP cell
- 5. Detection chamber
- 6. VS cell
- 7. Oxygen reference chamber
- 8. Adjusting resistor
- 9. Connector
- 10. ECM
- 11. Mixture control oxygen sensor signal processing circuit
- 12. CPU
- 13. Exhaust emission
- 14. Electrode