SENSOR




AIR FLOW SENSOR



Air flow sensor is installed in the air intake hose. Air flow sensor is composed of an extremely small heatsensing resistor. The air flow sensor controls the amount of electric current flowing into the heat sensing resistor to keep the heat sensing resistor at a constant temperature to the intake air temperature. When the air mass flow rate increases, the air flow speed is higher and also the amount of heat transfer from the heat sensing resistor to the air increased. Therefore, the air flow sensor increases the amount of electric current to the heat sensing resistor. Thus, the amount of electric current increases in accordance with the air mass flow rate. The air flow sensor measures the air mass flow rate by detecting the amount of electric current. The air flow sensor amplifies the detected electric current amount and outputs it into the engine-ECU. Engine-ECU uses this output current and engine speed to calculate and decide basic fuel injection time. Sensor properties are as shown in the figure.



INTAKE AIR TEMPERATURE SENSOR



Intake air temperature sensor is built in to the air flow sensor. Intake air temperature sensor detects intake air temperature through thermistor’s resistance change and outputs the voltage according to intake air temperature to engine-ECU. Engine-ECU uses this output voltage to compensate fuel injection control and ignition timing control. Sensor properties are as shown in the figure.



MANIFOLD ABSOLUTE PRESSURE SENSOR



The manifold absolute pressure sensor is installed in the inlet manifold. Manifold absolute pressure sensor uses a piezo resistive semiconductor to output the voltage according to manifold absolute pressure to engine-ECU. Engine-ECU uses this output voltage to compensate fuel injection volume according to manifold absolute pressure. Sensor properties are as shown in the figure.



ENGINE COOLANT TEMPERATURE SENSOR



The engine coolant temperature sensor is installed in the thermostat housing. Engine coolant temperature sensor uses thermistor’s resistance change to detect coolant temperature and output the voltage according to coolant temperature to engine-ECU. Engine-ECU uses this output voltage to appropriately control fuel injection volume, idle speed and ignition timing when the engine is cold. Sensor properties are as shown in the figure.



THROTTLE POSITION SENSOR



The throttle position sensor is installed in the throttle body. Throttle position sensor outputs voltage to engine-ECU based on the throttle shaft rotation angle. Engine-ECU uses this signal to detect the throttle valve opening angle to perform throttle valve control servo feedback control. This throttle position sensor uses Hall IC and is a non-contact type.

STRUCTURE AND SYSTEM


Throttle position sensor is composed of a permanent magnet fixed on the throttle shaft, Hall IC that outputs voltage according to magnetic flux density and a stator that efficiently introduces magnetic flux from the permanent magnet to Hall IC.
Magnetic flux density at Hall IC is proportional to the output voltage.
Throttle position sensor has 2 output systems - throttle position sensor (main) and throttle position sensor (sub), and the output voltage is output to engine-ECU. When throttle valve turns, output voltage of throttle position sensor (main) and throttle position sensor (sub) changes. This allows engine-ECU to detect actual throttle opening angle. Engine-ECU uses this output voltage for throttle valve control servo feedback control. The relationship between throttle opening angle and output voltage of the throttle position sensor (main) and throttle position sensor (sub) is as shown in the figure below.



When abnormality is detected




Engine-ECU compares output voltage of the throttle position sensor (main) and throttle position sensor (sub) to check for abnormality in the throttle position sensor. If the engine-ECU detects the abnormality, the emergency should be prevented by performing the fuel-safe control.

  • When 1-system malfunctions

    • The engine ECU should perform the throttle valve position control by only using the signal having no malfunctions. Depressing the accelerator pedal half way can perform the control. Performing the fuel cut can increase the engine rotation speed.

  • When 2-system malfunctions

    • The engine ECU should cut the energization of the throttle valve control servo. At that time, the spring built in the throttle valve can slightly open the throttle valve. This allows the engine ECU to control the engine output.

ACCELERATOR PEDAL POSITION SENSOR



Accelerator pedal position sensor is integrated with accelerator pedal, and detects accelerator opening angle. Engine-ECU uses the output voltage of this sensor to control appropriate throttle valve opening angle and fuel injection volume. This accelerator pedal position sensor uses Hall IC and is a non-contact type.

STRUCTURE AND SYSTEM



Accelerator pedal position sensor is composed of a permanent magnet fixed on the magnet carrier of the pedal shaft, Hall IC outputs voltage according to magnetic flux density and a stator that efficiently introduces magnetic flux from the permanent magnet to Hall IC.
Magnetic flux density at Hall IC is proportional to the output voltage.
The accelerator pedal position sensor has 2 output systems - accelerator pedal position sensor (main) and accelerator pedal position sensor (sub), and the output voltage is output to engine-ECU. According to depression of the accelerator pedal, output voltage of the accelerator pedal position sensor (main) and accelerator pedal position sensor (sub) changes. This allows engine-ECU to detect the actual accelerator pedal depression amount. Engine-ECU uses accelerator pedal position sensor (main) output voltage for appropriate throttle valve opening angle control and fuel injection volume control. Also, engine-ECU compares output voltage of the accelerator pedal position sensor (main) and accelerator pedal position sensor (sub) to check for abnormality in sensor. The relationship between accelerator opening angle and output voltage of the accelerator pedal position sensor (main) and accelerator pedal position sensor (sub) is as shown in the figure below.



When abnormality is detected




Engine-ECU compares output voltage of the accelerator pedal position sensor (main) and accelerator pedal position sensor (sub) to check for abnormality in sensor. If the engine-ECU detects the abnormality, the emergency should be prevented by performing the fuel-safe control.

  • When 1-system malfunctions

    • The engine-ECU should detect the amount of accelerator pedal depressed by only using the signal having no malfunctions. Depressing the accelerator pedal half way can perform the control. Performing the fuel cut can increase the engine rotation speed.

  • When 2-system malfunctions

    • The engine-ECU should cut the energization of the throttle valve control servo. At that time, the spring built in the throttle valve can slightly open the throttle valve. This allows the engine-ECU to control the engine output.

OXYGEN SENSOR



The oxygen sensor (front) is installed in the exhaust manifold. The oxygen sensor (rear) is installed in the exhaust front pipe.
Oxygen sensor has a built-in heater to help early activation of the sensor. This allows feedback control of air-fuel ratio soon after engine start.

This sensor uses the oxygen concentration cell principle of solid electrolyte (zirconia) and displays the property of sudden change in output voltage near theoretical air-fuel ratio. This property is used to detect oxygen density in exhaust gas. Feedback to engine-ECU allows it to judge whether air-fuel ratio is rich or lean compared to theoretical air-fuel ratio.
This allows engine-ECU precise feedback control to get theoretical air-fuel ratio with best cleaning efficiency of 3-way catalytic converter.



CRANK ANGLE SENSOR



A crank angle sensor is installed on the exhaust side of the cylinder block. The crank angle sensor monitors rotation of crankshaft sensing ring (36 teeth including 3 missing teeth) installed on the crankshaft and converts to voltage (pulse signal) that is output to engine-ECU. Engine-ECU uses crank angle sensor’s output pulse to detect crankshaft position.


The crank angle sensor uses a magnetic resistance element. When the vane of the crankshaft-sensing ring passes the front surface of the magnetic resistance element, the flux from the magnet passes the magnetic resistance element. Thus, resistance of the magnetic resistance element increases. When the vane of the crankshaft-sensing ring does not pass the front surface of the magnetic resistance element, the flux from the magnet does not pass the magnetic resistance element and the resistance decreases. The crank angle sensor converts this change in resistance of the magnetic resistance element to a 5 V pulse signal and outputs it to engine-ECU.



INLET CAMSHAFT POSITION SENSOR



The inlet camshaft position sensor is installed on the inlet side of the cylinder head. The inlet camshaft position sensor monitors shape of the half-moon sensing portion and converts to voltage (pulse signal) that is output to engine-ECU. Upon receiving this output voltage, the engine-ECU effects feedback control to optimize the phase of the inlet camshaft. Also, engine-ECU uses a combination of the camshaft position sensor output pulse signal and crankshaft position sensor output pulse signal to identify cylinders in the compression process.

The inlet camshaft position sensor uses a magnetic resistance element. When the camshaft position sensing portion passes the front surface of the magnetic resistance element, the flux from the magnet passes the magnetic resistance element. Thus, resistance of the magnetic resistance element increases. When the camshaft position sensing portion does not pass the front surface of the magnetic resistance element, the flux from the magnet does not pass the magnetic resistance element and the resistance decreases. The inlet camshaft position sensor converts this change in resistance of the magnetic resistance element to a 5 V pulse signal and outputs it to engine-ECU.



DETONATION SENSOR



A detonation sensor is installed on the inlet side of the cylinder block. Detonation sensor uses the piezoelectric element to convert the vibration of the cylinder block generated when engine is in operation to minute voltage that is output to engine-ECU. Engine-ECU uses the minute output voltage from the detonation sensor filtered through the cylinder block’s natural frequency to detect knocking, and compensates the ignition timing lag according to the strength of the knocking.



BAROMETRIC PRESSURE SENSOR



A barometric pressure sensor is built into engine-ECU. The barometric pressure sensor is a semiconductor diffused pressure element which outputs voltage to engine-ECU according to atmospheric pressure. Engine-ECU uses this output voltage to sense the altitude of the vehicle and compensates fuel injection volume to achieve the appropriate air-fuel ratio for that altitude.

OIL PRESSURE SWITCH



The oil pressure switch is installed on the inlet side of the cylinder block. The oil pressure switch detects whether the oil pressure is high or low using the contact switch. When the oil pressure becomes higher than the specified value after the engine starts, the contact point of the oil pressure switch opens.
This allows the engine-ECU to detect the oil pressure is higher than the specified value. The engine-ECU outputs the OFF signal to the combination meter through the CAN and then turns off the oil pressure warning lamp.



ALTERNATOR FR TERMINAL


Alternator turns ON/OFF the power transistor in the voltage regulator to adjust current flow in the field coil according to alternator output current. In this way alternator output voltage is kept adjusted (to about 14.4 V). The ratio of power transistor ON time (ON duty) is output from alternator FR terminal to engine-ECU. Engine-ECU uses this signal to detect alternator output current and drives throttle valve control servo according to output current (electric load). This prevents change in idle speed due to electric load and helps maintain stable idle speed.



ALTERNATOR L TERMINAL


After turning on the ignition switch, the current is input by the engine-ECU to the alternator L terminal. This allows the voltage regulator to be on and the field coil to be excited. When the alternator rotates in this situation, the voltage is excited in the stator coil and the current is output from B-terminal through the commutation diode. Also the generated voltage is input to the voltage regulator through the commutation diode. After the electric generation begins, the current is supplied to the field coil from this circuit. In addition, the generated voltage is output from the alternator L terminal to the engine-ECU. This allows the engine-ECU to detect that the electric generation begins. The engine-ECU outputs the ON signal to the combination meter through the CAN and then turns off the charge lamp.