3UR-FE ENGINE

The configuration of the engine control system is as shown in the following chart.

Crank Position Sensor, Cam Position Sensor and VVT Sensor

1. General

   
   

   • Magnetic Resistance Element (MRE) sensors are used for the crank position, cam position, and VVT sensors.

   • The timing rotor for the crank position sensor is installed on the back end of the crankshaft. The timing rotor has 34 teeth, with 2 teeth missing, at 10° intervals. Based on these teeth, the crank position sensor transmits crankshaft position signals (NE signal) consisting of 33 high/low output pulses every 10° per revolution of the crankshaft, and 1 high/low output pulse every 30°. The ECM uses the NE signal for detecting the crankshaft position as well as for detecting the engine speed. It uses the missing teeth signal for determining the top-dead-center.

   • The cam position sensor uses a timing rotor that is installed on the front end of the intake camshaft sprocket of the left bank. Based on the timing rotor, the sensor outputs camshaft position signals (G2 signal) consisting of 3 (3 high output, 3 low output) pulses for every 2 revolutions of the crankshaft. The ECM compares the G2 and NE signals to detect the camshaft position and identify the cylinder.

   • The VVT sensors (intake and exhaust) use timing rotors that are installed on the intake and exhaust camshafts of each bank. Based on the timing rotors, the sensors output VVT position signals consisting of 3 (3 high output, 3 low output) pulses for every 2 revolutions of the crankshaft. The ECM compares these VVT position signals to the NE signal to detect the actual valve timing.

     

     *1	Cam Position Sensor	*2	Timing Rotor
     *3	VVT Sensor (Intake)	*4	VVT Sensor (Exhaust)
     *5	Crank Position Sensor	-	-
     *a	Bank 1	-	-

     Figure 1. Wiring Diagram (Crank Position Sensor Circuit)

     

     *1	Crank Position Sensor
     *2	Timing Rotor

     Figure 2. Sensor Output Waveforms

     

2. MRE Type Sensor

   
   

   • The MRE type sensor consists of an MRE, a magnet and a sensor.

   • The direction of the magnetic field changes due to the profile (protruding and non-protruding portions) of the timing rotor, which passes by the sensor. As a result, the resistance of the MRE changes, and the output voltage to the ECM changes to high or low. The ECM detects the crankshaft and camshaft position based on this output voltage.

   • The differences between the MRE type sensor and the pick-up coil type sensor used on a conventional model are as follows.

   
   

   • An MRE type sensor outputs a constant level of high/low digital signals regardless of the engine speed. Therefore, an MRE type sensor can detect the positions of the crankshaft and camshaft at an early stage of cranking.

   • A pickup coil type sensor outputs analog signals with levels that change with the engine speed.

     Figure 3. MRE Type and Pick-up Coil Type Output Waveform Image Comparison

     

Accelerator Pedal Sensor Assembly

1. The no-contact type accelerator pedal sensor assembly uses a Hall IC, which is mounted on the accelerator pedal arm.

2. 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 that occur in the magnetic flux into electrical signals, and outputs them in the form of accelerator pedal position signals to the ECM.

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

   

   *1	Hall IC	*2	Magnetic Yoke
   *3	Accelerator Pedal Arm	-	-

   

Throttle Position Sensor

1. The no-contact type throttle position sensor uses a Hall IC, which is mounted on the throttle body.

2. 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.

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

   

   *1	Magnet	*2	Hall IC
   *a	Cross Section	-	-

   

Knock Control Sensor (Flat Type)

1. General

   
   

   • In the conventional type knock control sensor (resonant type), a vibration plate, which has the same resonance point as the knocking frequency of the engine, is built in and can detect the vibration in this frequency band.

   • On the other hand, a flat type knock control sensor (non-resonant type) has the ability to detect vibration in a wider frequency band from approximately 6 kHz to 15 kHz, and has the following features:

   
   

   • The engine knocking frequency will change slightly depending on the engine speed. The flat type knock control sensor can detect vibration even when the engine knocking frequency is changed. Thus the vibration detection ability is increased compared to the conventional type knock control sensor, and a more precise ignition timing control is possible.

     Figure 4. Characteristic of Knock Control Sensor

     

2. Construction

   
   

   • The flat type knock control sensor is installed on the engine through the stud bolt installed on the cylinder block. For this reason, a hole for the stud bolt runs through the center of the sensor.

   • Inside of the sensor, a steel weight is located on the upper portion and a piezoelectric element is located under the weight through the insulator.

   • The open/short circuit detection resistor is integrated.

     

     *A	Flat Type Knock Control Sensor (Non-resonant Type)	*B	Conventional Type Knock Control Sensor (Resonant Type)
     *1	Steel Weight	*2	Insulator
     *3	Piezoelectric Element	*4	Open/Short Circuit Detection Resistor
     *5	Vibration Plate	-	-

3. Operation

   
   

   • The knocking vibration is transmitted to the steel weight and its inertia applies pressure to the piezoelectric element. This action generates electromotive force (voltage).

     

     *1	Steel Weight	*2	Piezoelectric Element
     *a	Inertia	-	-

4. Open/Short Circuit Detection Resistor

   
   

   • While the engine switch is on (IG), the open/short circuit detection resistor in the knock control sensor and the resistor in the ECM keep the voltage at the terminal KNK1 of engine constant.

   • An Integrated Circuit (IC) in the ECM constantly monitors the voltage of the terminal KNK1. If the open/short circuit occurs between the knock control sensor and the ECM, the voltage of the terminal KNK1 changes and the ECM detects the open/short circuit and stores a DTC (Diagnostic Trouble Code).

     

     *1	Piezoelectric Element
     *2	Knock Control Sensor (Bank 1, Sensor 1)
     *3	Open/Short Circuit Detection Resistor

   Tech Tips

   These knock control sensors are mounted in specific directions at specific angles. To prevent the right and left bank wiring connectors from being interchanged, make sure to install each sensor in its prescribed direction. For details, refer to the Repair Manual.

Air Fuel Ratio Sensor and Oxygen Sensor

1. General

   
   

   • The oxygen sensor and the air fuel ratio sensor differ in output characteristics.

   • The output voltage of the oxygen sensor changes in accordance with the oxygen concentration in the exhaust gas. The ECM uses this output voltage to determine whether the present air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio.

   • Approximately 0.4 V is constantly applied to the air fuel ratio sensor, which outputs an amperage that varies in accordance with the oxygen concentration in the exhaust gas. The ECM converts the changes in the output amperage into voltage in order to linearly detect the present air-fuel ratio.

     

2. Construction

   
   

   • 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, in accordance with the different types of heater construction that are used.

   • The cup type sensor contains a sensor element that surrounds a heater.

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

     

     *A	Air Fuel Ratio Sensor (Planar Type)	*B	Oxygen Sensor (Cup Type)
     *1	Dilation Layer	*2	Alumina
     *3	Platinum Electrode	*4	Sensor Element (Zirconia)
     *5	Heater	*6	Atmosphere

     The illustrations above are intended to show the differences in the basic construction between the cup type sensor and the planner type sensor, so the illustrated sensor shapes may differ from the actual ones.

Control

1. General

   
   

   • The ETCS-i consists of the following functions:

   
   

   • Normal Throttle Control (non-linear control)

   • Idle Speed Control (ISC)

   • Active Traction Control (A-TRC)

   • Vehicle Stability Control (VSC) Coordination Control

   • Crawl Control (CRAWL) Coordination Control

   • Cruise Control

   • Dynamic Radar Cruise Control*

   
   

   • *: Models with dynamic radar cruise control system

2. Normal Throttle Control (Non-linear Control)

   
   

   1. General

   
   

   • Controls the throttle to an optimal throttle valve angle that is appropriate for the driving conditions such as the amount of the accelerator pedal effort and the engine speed in order to achieve excellent throttle control and comfort in all operating ranges.

     Figure 6. Conceptual Diagrams of Engine Control During Acceleration and Deceleration

     

   2. 2nd Start Control

   
   

   • In situations in which low-μ (low friction) road surface conditions can be anticipated, such as when the vehicle is driving in the snow, the rate of throttle valve opening can be controlled to ensure vehicle stability while the vehicle is driving on a slippery surface. This is accomplished by turning on 2nd start control. Pressing the 2nd side of the pattern select switch activates this control. This control modifies the relationship and reaction of the throttle to the accelerator pedal, and assists the driver by reducing the engine output from that of a normal level.

3. Idle Speed Control

   
   

   • The ECM controls the throttle valve in order to constantly maintain an ideal idle speed.

4. A-TRC

   
   

   • As part of the A-TRC, the throttle valve opening is reduced by a demand signal sent from the skid control ECU to the ECM. This demand signal will be sent if an excessive amount of slippage occurs at a drive wheel, thus ensuring vehicle stability and applying the appropriate amount of power to the road.

5. VSC Coordination Control

   
   

   • In order to bring the effectiveness of the VSC into full play, the throttle valve angle is regulated through a coordination control with the skid control ECU.

6. CRAWL Coordination Control

   
   

   • While the CRAWL is operating, the throttle valve is regulated through a coordination control with the skid control ECU.

7. Cruise Control

   
   

   • The ECM directly actuates the throttle valve for operation of the cruise control.

8. Dynamic Radar Cruise Control*

   
   

   • The dynamic radar cruise control uses a millimeter wave radar sensor and the distance control ECU to determine the distance, direction, and relative speed to a vehicle ahead. Thus, the system can effect deceleration control, follow-up control, constant speed control, and acceleration control. To make these controls possible, the ECM controls the throttle valve.

   
   

   • *: Models with dynamic radar cruise control system

Operation

1. Advance

   
   

   • When the camshaft timing oil control valve 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.

     Figure 9. Intake Side

     

     *1	Vane	*2	ECM
     *a	Rotation Direction	*b	Oil Pressure
     *c	In	*d	Drain

     Figure 10. Exhaust Side

     

     *1	Vane	*2	ECM
     *a	Rotation Direction	*b	Oil Pressure
     *c	In	*d	Drain

2. Retard

   
   

   • When the camshaft timing oil control valve 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.

     Figure 11. Intake Side

     

     *1	Vane	*2	ECM
     *a	Rotation Direction	*b	Drain
     *c	In	*d	Oil Pressure

     Figure 12. Exhaust Side

     

     *1	Vane	*2	ECM
     *a	Rotation Direction	*b	Drain
     *c	In	*d	Oil Pressure

3. Hold

   
   

   • After reaching the target timing, the engine valve timing is maintained by keeping the camshaft timing oil control valve 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 oil control valve.

Intake Air Control Valve and ACIS Actuator

1. The intake air control valve and ACIS actuator are integrated with the intake manifold. This valve opens and closes to change the effective length of the intake manifold in two stages.

   

   *1	Intake Air Control Valve	*2	ACIS Actuator
   *a	Front	-	-

Operation

1. When the Intake Control Valve Closes (VSV On)

   
   

   • The ECM activates the VSV so that the negative pressure acts on the diaphragm chamber of the actuator. This closes the control valve to match the longer pulsation cycle. As a result, the effective length of the intake manifold is lengthened and the intake efficiency in the low-to-medium engine speed range under heavy load is improved due to the dynamic effect of the intake air, thereby increasing the power output.

     

2. When the Intake Control Valve Opens (VSV Off)

   
   

   • The ECM deactivates the VSV so that atmospheric air is led into the diaphragm chamber of the actuator. This opens the control valve to match the shorter pulsation cycle. When the control valve is open, the effective length of the intake manifold is shortened and peak intake efficiency is shifted. This benefits the low, medium and high engine speed ranges at low loads and the high engine speed range under heavy load, thus providing greater output at high engine speeds.

     

Construction and Operation

1. Air Pump

   
   

   • Each air pump consists of a DC motor, an impeller and an air filter.

   
   

   • The air pump supplies air into an air injection control valve using its impeller.

   • The air filter is maintenance-free.

   • The structure and function of the air pumps for the bank 1 and bank 2 are basically the same.

   

   *1	Air Pump (Bank 2)	*2	Air Pump (Bank 1)
   *3	Impeller	*4	DC Motor
   *5	Air Filter	-	-
   *a	Air In	*b	Air Out
   *c	Cross Section	-	-

2. Air Switching Valve

   
   

   • The air switching valve is operated by a solenoid coil to control air injection and prevent back-flow of exhaust gas. Opening timing of the valve is synchronized with the operation timing of the air pump.

   • An air pressure sensor is built into the corresponding air switching valve.

   • The structure and function of the air switching valves for the bank 1 and bank 2 are basically the same.

     

     *1	Air Switching Valve (Bank 2)	*2	Air Switching Valve (Bank 1)
     *3	Valve	*4	Solenoid Coil
     *a	Air Out	*b	Air In
     *c	Cross Section (for Bank 1)	-	-

3. Air Pressure Sensor

   
   

   • The air pressure sensor consists of a semiconductor, which has a silicon chip that changes its electrical resistance when pressure is applied to it. The sensor converts the pressure into an electrical signal, and sends it to the ECM in an amplified form.

   • The structure and function of the air pressure sensors for the bank 1 and bank 2 are basically the same.

     

   • The ECM detects operation of the air injection system based on signals from the air pressure sensor as follows:

   
   

   1. When the air pump is on and the air switching valve is closed, the pressure is stable.

   2. When the air pump is on and the air switching valve is open, the pressure drops slightly and becomes unstable because of exhaust pulses.

   3. When the air pump is off and the air switching valve is closed, the pressure remains at atmospheric pressure.

   4. When the air pump is off and air switching valve is open, the pressure drops below atmospheric pressure and becomes unstable because of exhaust pulses.

      

4. Air Injection Control Driver

   
   

   • A semiconductor type air injection control driver is used. Activated by the ECM, this driver actuates the air pump and the air switching valve.

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

   • The basic functions of the air injection control drivers for the bank 1 and bank 2 are the same. The following system chart shows the bank 1 (left bank).

     

     DI Terminal Output

     Condition	AIRP	AIRV	Output (Duty Cycle Signal)
     Open circuit in line between AIDI and DI terminals.	-	-
     Failure in line between ECM terminals and air injection control driver.	-	-
     Output failure at air injection control driver. (Failure in air pump actuation circuit)	-	-	*1 200 ms
     Output failure at air injection control driver. (Failure in air switching valve actuation circuit)	-	-
     Overheat failure of air injection control driver.	-	-
     Normal	On	On
     	Off	Off
     	On	Off
     	Off	On

Operation

1. As indicated in the timing chart below, when the ECM detects an STSW signal (start signal) from the main body ECU, the ECM outputs a STAR signal (starter relay drive signal) through the starter cut relay to the starter relay and actuates the starter. The ECM also outputs an ACCR signal (ACC cut request signal) to the main body ECU. Thus, the main body ECU will not energize the ACC relay.

2. After the starter operates and the engine speed becomes higher than approximately 500 rpm, the ECM determines that the engine has started and stops the output of the STAR signal to the starter relay and the output of the ACCR signal to the main body ECU. Thus, the starter operation stops and the main body ECU energizes the ACC relay.

3. If the engine has any failure and does not start, the starter operates as long as its maximum continuous operation time and stops automatically. The maximum continuous operation time is approximately 2 seconds through 25 seconds depending on the engine coolant temperature condition. When the engine coolant temperature is extremely low, it is approximately 25 seconds and when the engine is warmed up sufficiently, it is approximately 2 seconds.

4. This system cuts off the current that powers the accessories while the engine is cranking to prevent the accessory illumination from operating intermittently due to the unstable voltage that is associated with the cranking of the engine.

5. This system has the following protection features:

   
   

   • While the engine is running normally, the starter does not operate.

   • Even if the driver keeps pressing the engine switch, the ECM stops the output of the STAR and ACCR signals when the engine speed becomes higher than 1200 rpm. Thus, the starter operation stops and the main body ECU energizes the ACC relay.

   • In case the driver keeps pressing the engine switch and the engine does not start, the ECM stops the output of the STAR and ACCR signals after 30 seconds have elapsed. Thus, the starter operation stops and the main body ECU energizes the ACC relay.

   • In case the ECM cannot detect an engine speed signal while the starter is operating, the ECM will immediately stop the output of the STAR and ACCR signals. Thus, the starter operation stops and the main body ECU energizes the ACC relay.

     Figure 17. Timing Chart