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Air flow sensor is installed in the air intake hose. Air flow sensor is composed of an
extremely small heat sensing 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 is 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.
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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.
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Manifold absolute pressure sensor is installed in inlet manifold plenum. 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.
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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. Sensor
properties are as shown in the figure.
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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 of non-contact type.
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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.
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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. Also, 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. 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.
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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 of non-contact type.
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Accelerator pedal position sensor is composed of a permanent magnet fixed on the magnet
carrier of the pedal 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.
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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.
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Oxygen sensors are installed in 2 positions (front, rear) on both the right bank catalytic
converter and left bank catalytic converter. Oxygen sensor has a built-in heater to help early activation
of the sensor. This allows feedback control of air-fuel ratio soon after start.
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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.
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This allows engine-ECU precise feedback control to get theoretical air-fuel ratio with
best cleaning efficiency of 3-way catalytic converter.
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A crank angle sensor is installed to the right bank side on the cylinder block. The crank
angle sensor monitors rotation of crankshaft sensing blade (36 teeth including 4 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 crank angle.
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The crank angle sensor uses a magnetic resistance element. When the vane of the crankshaft-sensing
blade 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 blade 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.
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A camshaft position sensor is installed on the camshaft position sensor support on left
bank side. The camshaft position sensor monitors rotation of the camshaft position-sensing cylinder
(7 teeth) and converts to voltage (pulse signal) that is output to engine-ECU. Engine-ECU uses
a combination of the camshaft position sensor output pulse signal and crank angle sensor output
pulse signal to identify cylinders in the compression process.
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The camshaft position sensor uses a magnetic resistance element. When the vane of the
camshaft position-sensing cylinder passes the front surface of the magnetic resistance element,
the flux from the magnet passes the magnetic resistance element. Thus, the resistance of the
magnetic resistance element increases. When the vane of the camshaft position-sensing cylinder
does not pass the front surface of the magnetic resistance element, the flux from the magnet
does not pass to magnetic resistance element and resistance decreases. The camshaft position
sensor converts this change in resistance of the magnetic resistance element to a 5 V pulse signal
and outputs the signal to engine-ECU.
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A detonation sensor is installed on the cylinder block (both right bank side and left
bank side). Detonation sensor uses the piezo electric 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.
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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 get the appropriate air-fuel ratio for that altitude.
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The engine oil pressure switch (for warning lamp) is installed to the cylinder block at
the left side.
The engine oil pressure switch (for warning lamp) 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 engine oil pressure switch (for warning
lamp) 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.
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An engine oil pressure switch (for MIVEC) is installed on the oil feeder control valve
housing. The engine oil pressure switch (for MIVEC) uses contact switch to detect High/Low of
oil pressure. When the oil feeder control valve functions and oil pressure in the oil path rises
above a prescribed value the contact point of the engine oil pressure switch (for MIVEC) opens.
Thus, engine-ECU detects that oil pressure is above the prescribed value and checks that MIVEC
is functioning.
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A power steering fluid pressure switch is installed on the power steering oil pump. The
power steering fluid pressure switch uses a contact switch to detect the power steering fluid pressure.
When power steering oil pressure rises due to operation of the steering wheel, the power steering
load switch outputs an ON signal to engine-ECU. Engine-ECU performs idle-up according to the
voltage and prevents reduction in engine speed due to power steering load and so maintains stable
idle speed.
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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’s
output voltage is kept adjusted (to about 14.7 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’s 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.
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After turning on the ignition switch, the current is input by the engine-ECU to the alternator
L terminal. This allows the IC 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.
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