Description
System Readiness Test (SRT) codes indicate whether self-diagnostic tests for non-continuously monitored components have been completed or are incomplete. Inspection/Maintenance (I/M) tests of the On-Board Diagnostic II (OBD-II) type emission systems may become the legal requirements in some states/areas. All SRT codes must be set, or complete, prior to performing an I/M test. See SETTING SRT CODES .
If diagnostic information is erased or battery is disconnected for a prolonged period of time, vehicle must be driven in the manner prescribed to set all SRT codes. SRT codes are set after component self-diagnosis has been performed one or more times. SRT codes are set whether component diagnosis is good or bad, and whether or not diagnosis is performed in consecutive trips. See SETTING SRT CODES .
Accelerator pedal released position learning is an operation to learn the fully released position of the accelerator pedal by monitoring the accelerator pedal position sensor output signal. It must be performed each time harness connector of accelerator pedal position sensor or ECM is disconnected.
Throttle valve closed position learning is an operation to learn the fully closed position of the throttle valve by monitoring the throttle position sensor output signal. It must be performed each time electronic throttle control actuator harness connector or ECM harness connector is disconnected.
The mechanism hydraulically controls cam phases continuously with the fixed operating angle of the intake valve. The ECM receives signals such as crankshaft position, camshaft position, engine speed, and engine coolant temperature. Then, the ECM sends on/off pulse duty signals to the IVT control solenoid valve depending on driving status. This makes it possible to control the shut/open timing of the intake valve to increase engine torque in low/mid speed range and output in high-speed range.
Intake Valve Timing (IVT) control solenoid valve is activated by on/off pulse duty (ratio) signals from the ECM. The IVT control solenoid valve changes the oil amount and direction of flow through intake valve timing control unit or stops oil flow. The longer pulse width advances valve angle. The shorter pulse width retards valve angle. When on and off pulse widths become equal, the solenoid valve stops oil pressure flow to fix the intake valve angle at the control position.
ECM control of HO2S1 heaters is based on engine speed input. Heaters are off when engine speed is more than 3600 RPM and on when engine speed is less than 3600 RPM.
ECM control of HO2S2 heaters is based on engine speed input. Heaters are off when engine speed is more than 3600 RPM and on when engine speed is less than 3600 RPM.
The Mass Airflow Sensor (MAF) is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature of the hot film as air flow increases. The ECM detects the air flow by means of this current change.
The Mass Airflow (MAF) sensor is placed in the stream of intake air. It measures the intake flow rate by measuring a part of the entire intake flow. It consists of a hot film that is supplied with electric current from the ECM. The temperature of the hot film is controlled by the ECM a certain amount. The heat generated by the hot film is reduced as the intake air flows around it. The more air, the greater the heat loss. Therefore, the ECM must supply more electric current to maintain the temperature of the hot film as air flow increases. The ECM detects the air flow by means of this current change.
The Intake Air Temperature (IAT) sensor is built into Mass Airflow (MAF) sensor. The sensor detects intake air temperature and transmits a signal to the ECM. The temperature sensing unit uses a thermistor which is sensitive to the change in temperature. Electrical resistance of the thermistor decreases in response to the temperature rise.
The Engine Coolant Temperature (ECT) sensor is used to detect the engine coolant temperature. The sensor modifies a voltage signal from the ECM. The modified signal returns to the ECM as the engine coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
Electric Throttle Control Actuator consists of throttle control motor, Accelerator Pedal Position (APP) sensor, Throttle Position (TP) sensor, etc. The TP sensor responds to the throttle valve movement. The TP sensor has 2 sensors. These sensors are a kind of potentiometers which transform the throttle valve position into output voltage, and emit the voltage signal to the ECM. (Scheme 14) In addition, these sensors detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle correct in response to driving condition.
Scheme 14
The Intake Air Temperature (IAT) sensor is built into Mass Airflow (MAF) sensor. The sensor detects intake air temperature and transmits a signal to the ECM. The temperature sensing unit uses a thermistor which is sensitive to the change in temperature. Electrical resistance of the thermistor decreases in response to the temperature rise.
Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough. This is due to a leak in a seal or the thermostat is stuck open.
The front Heated Oxygen Sensors (HO2S) are located in each front exhaust pipe, upstream of catalyst. They detect the amount of oxygen in the exhaust gas compared to the outside air. The front HO2S has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. The front HO2S signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from one volt to zero volts.
To judge the malfunction, the diagnosis checks that the HO2S1 output is not inordinately high.
The front Heated Oxygen Sensors (HO2S) are located in each front exhaust pipe, upstream of catalyst. They detect the amount of oxygen in the exhaust gas compared to the outside air. The front HO2S has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. The front HO2S signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from one volt to zero volts.
To judge the malfunction of HO2S1, this diagnosis measures response time of HO2S1 signal. The time is compensated by engine operating (speed and load), fuel feedback control constant, and HO2S1 temperature index. Judgment is based on whether the compensated time (HO2S1 cycling time index) is inordinately long or not.
The front Heated Oxygen Sensors (HO2S) are located in each front exhaust manifold, upstream of catalyst. They detect the amount of oxygen in the exhaust gas compared to the outside air. The front HO2S has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. The front HO2S signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from one volt to zero volts.
Under the condition in which the front HO2S signal is not input, the ECM circuits will read about .3 volt continuously. Therefore, for this diagnosis, the time that output voltage is 200-400 millivolts is monitored, and the diagnosis checks that this time is not inordinately long.
HO2S2, located after 3-way catalyst, monitors the oxygen level in the exhaust gas on each bank. Even if switching characteristics of HO2S1 are shifted, the air fuel ratio is controlled to stoichiometric, by the signal from HO2S2. This sensor is made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. Under normal conditions, HO2S2 is not used for engine control. HO2S2 has a much longer switching time between rich and lean than HO2S1. The oxygen storage capacity before the 3-way catalyst causes the longer switching time.
To judge the malfunctions of HO2S2, ECM monitors whether the minimum voltage of sensor is sufficiently high during the various driving condition such as fuel-cut.
HO2S2, located after 3-way catalyst, monitors the oxygen level in the exhaust gas on each bank. Even if switching characteristics of HO2S1 are shifted, the air fuel ratio is controlled to stoichiometric, by the signal from HO2S2. This sensor is made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. Under normal conditions, HO2S2 is not used for engine control. HO2S2 has a much longer switching time between rich and lean than HO2S1. The oxygen storage capacity before the 3-way catalyst causes the longer switching time.
To judge the malfunctions of HO2S2, ECM monitors whether the switching response of the sensor's voltage is faster than specified during the various driving condition such as fuel-cut.
With the air/fuel mixture ratio self-learning control, the actual mixture can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the front Heated Oxygen Sensor (HO2S). The ECM calculates the necessary compensation to correct the offset between the actual and theoretical ratios.
When the amount of compensation is extremely large (the actual mixture is too lean), the ECM determines that the fuel injection system is malfunctioning and turns on the MIL (2-trip detection logic).
With the air/fuel mixture ratio self-learning control, the actual mixture can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the front Heated Oxygen Sensor (HO2S). The ECM calculates the necessary compensation to correct the offset between the actual and theoretical ratios.
When the amount of compensation is extremely large (the actual mixture is too rich), the ECM determines that the fuel injection system is malfunctioning and turns on the MIL (2-trip detection logic).
The Fuel Tank Temperature (FTT) sensor is used to detect the fuel temperature inside the fuel tank. The sensor modifies a voltage signal from the ECM. The modified signal returns to the ECM as the fuel temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
When a misfire occurs, engine speed will fluctuate (vary). If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor to vary, ECM can detect a misfire. The misfire detection logic consists of the following 2 conditions.
- One Trip Detection Logic (3-Way Catalyst Damage) On the first trip that a misfire condition occurs that can damage the 3-way catalyst due to overheating, the MIL will blink. When a misfire condition occurs, the ECM monitors the CKP sensor signal every 200 engine revolutions for a change. When the misfire condition decreases to a level that will not damage the catalyst, the MIL will turn off. If another misfire condition occurs that can damage the catalyst on a second trip, the MIL will blink. When the misfire condition decreases to a level that will not damage the catalyst, the MIL will remain on. If another misfire condition occurs that can damage the catalyst, the MIL will begin to blink again.
- Two Trip Detection Logic (Exhaust Quality Deterioration) For misfire conditions that will not cause damage to the catalyst (but will affect vehicle emissions), the MIL will only light when the misfire is detected on a second trip. During this condition, the ECM monitors the CKP sensor signal every 1000 engine revolutions. A misfire malfunction can be detected on any one cylinder or on multiple cylinders.
The knock sensor is attached to the cylinder block. It senses engine knocking using a piezoelectric element. A knocking vibration from the cylinder block is sensed as vibrational pressure. This pressure is converted into a voltage signal and sent to the ECM.
Note. Freeze frame data will not be stored in ECM and MIL will not illuminate for the knock sensor. Knock sensor has one-trip detection logic.
The Crankshaft Position (CKP) Sensor (POS) is located on the cylinder block rear housing facing the gear teeth of the signal plate at the end of the crankshaft. It detects the fluctuation of the engine revolution. The sensor consists of a permanent magnet and hall integrated circuit. When the engine is running, the high and low parts of the teeth cause the gap with the sensor to change. The changing gap causes the magnetic field near the sensor to change. Due to the changing magnetic field, the voltage from the sensor changes. The ECM receives the voltage signal and detects the fluctuation of the engine revolution.
The Camshaft Position (CMP) sensor (PHASE) senses the protrusion with exhaust valve cam sprocket to identify a particular cylinder. The Crankshaft Position (CKP) sensor (POS) senses the piston position. When the CKP sensor (POS) system becomes inoperative, the CMP sensor (PHASE) provides various controls of engine parts instead, utilizing timing of cylinder identification signals.
The sensor consists of a permanent magnet and Hall integrated circuit. When engine is running, the high and low parts of the teeth cause the gap with the sensor to change. The changing gap causes the magnetic field near the sensor to change. Due to the changing magnetic field, the voltage from the sensor changes.
The ECM monitors the switching frequency ratio of Heated Oxygen Sensors (HO2S) 1 (front) and 2 (rear). A 3-way catalyst with high oxygen storage capacity will indicate a low switching frequency of HO2S2 (rear). As oxygen storage capacity decreases, HO2S2 switching frequency will increase. When the frequency ratio of HO2S 1 (front) and 2 (rear) approaches a specified limit value, the 3-way catalyst malfunction is diagnosed.
In this evaporative emission (EVAP) control system, purge flow occurs during non-closed throttle conditions. Purge volume is related to air intake volume. Under normal purge conditions (non-closed throttle), the EVAP canister purge volume control solenoid valve is open to admit purge flow. Purge flow exposes the EVAP control system pressure sensor to intake manifold vacuum. Under normal conditions (non-closed throttle), sensor output voltage indicates if pressure drop and purge flow are adequate. If not, a malfunction is determined.
Note. If DTC P0442, P0455 or P1442 is displayed with P1448, first perform trouble diagnosis for DTC P1448. See DTC P1448: EVAP CANISTER VENT CONTROL VALVE (OPEN) .
For DTC P0442, this diagnosis detects leaks in the EVAP purge line using engine intake manifold vacuum. If pressure does not increase, the ECM will check for leaks in the line between the fuel tank and EVAP canister purge volume control solenoid valve, under the following conditions: The vacuum cut valve by-pass valve is opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP canister vent control valve will then be closed to shut the EVAP purge line off. The EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line using intake manifold vacuum. After this occurs, the EVAP canister purge volume control solenoid valve will be closed.
For DTC P0455, this diagnosis detects a very large leak (fuel filler cap fell off etc.) in EVAP system between the fuel tank and EVAP canister purge volume control solenoid valve.
For DTC 1442, this diagnosis detects leaks in the EVAP purge line using vapor pressure in the fuel tank. The EVAP canister vent control valve is closed to shut the EVAP purge line. The vacuum cut valve by-pass valve will then be opened to clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve. The EVAP control system pressure sensor can now monitor the pressure inside the fuel tank. If pressure increases, the ECM will check for leaks in the line between the vacuum cut valve and EVAP canister purge volume control solenoid valve.
This system controls flow rate of fuel vapor from the EVAP canister. The opening of the vapor by-pass passage in the EVAP canister purge volume control solenoid valve changes to control the flow rate. The EVAP canister purge volume control solenoid valve repeats on/off operation according to the signal sent from the ECM. The opening of the valve varies for optimum engine control. The optimum value stored in the ECM is determined by considering various engine conditions. When the engine is operating, the flow rate of fuel vapor from the EVAP canister is regulated as the air flow changes.
The EVAP canister purge volume control solenoid valve uses a on/off duty to control the flow rate of fuel vapor from the EVAP canister. The EVAP canister purge volume control solenoid valve is moved by on/off pulses from the ECM. The longer the on pulse, the greater the amount of fuel vapor that will flow through the valve.
The EVAP Canister Vent Control Valve (EVAP-CVCV) is located on the EVAP canister and is used to seal the canister vent. This solenoid valve responds to signals from the ECM. When the ECM sends an ON signal, the coil in the solenoid valve is energized. A plunger will then move to seal the canister vent. The ability to seal the vent is necessary for the on board diagnosis of other evaporative emission control system components. This solenoid valve is used only for diagnosis, and usually remains opened. When the vent is closed, under normal purge conditions, the evaporative emission control system is depressurized and allows "EVAP Control System (Small Leak)" diagnosis.
The EVAP control system pressure sensor detects pressure in the purge line. The sensor output voltage to the ECM increases as pressure increases.
The EVAP control system pressure sensor detects pressure in the purge line. The sensor output voltage to the ECM increases as pressure increases.
For DTC P0456, this diagnosis detects very small leaks in the EVAP line between fuel tank and EVAP canister purge volume control solenoid valve, using the intake manifold vacuum in the same way as conventional EVAP small leak diagnosis. If ECM judges a leak which corresponds to a very small leak, DTC P0456 will be detected. If ECM judges a leak equivalent to a small leak, EVAP DTC P0442 will be detected. If ECM judges there are no leaks, the diagnosis will be okay.
For DTC P1456, this diagnosis detects very small leaks in the EVAP line between fuel tank and EVAP canister purge volume control solenoid valve, using vapor pressure in the fuel tank in the same way as conventional EVAP small leak diagnosis. If ECM judges a leak which corresponds to a very small leak, DTC P1456 will be detected. If ECM judges a leak equivalent to a small leak, EVAP DTC P1442 will be detected. If ECM judges there are no leaks, the diagnosis will be okay.
The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is a mechanical float and the other side is a variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.
When the vehicle is parked, naturally the fuel level in the fuel tank is stable. It means that output signal of the fuel level sensor does not change. If ECM senses sloshing signal from the sensor, fuel level sensor malfunction is detected. Malfunction is detected when even though the vehicle is parked, a signal being varied is sent from the fuel level sensor to ECM.
The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is a mechanical float and the other side is a variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.
Driving long distances naturally affects fuel gauge level. This diagnosis detects the fuel gauge malfunction of the gauge not moving even after a long distance has been driven.
The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is a mechanical float and the other side is a variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.
ECM receives 2 signals from the fuel level sensor circuit. One is fuel level sensor power supply circuit, and the other is fuel level sensor ground circuit. This diagnosis is used to detect open or short circuit malfunction.
The vehicle speed signal is sent to the instrument cluster from the VDC/TCS/ABS control unit via the Controller Area Network (CAN) communication line. The instrument cluster then sends a signal to the ECM via the CAN communication line.
The ECM controls the engine idle speed to a specified level through the fine adjustment of the air, which is let into the intake manifold, by operating the electric throttle control actuator. The operating of the throttle valve is varied to allow for optimum control of the engine idling speed. The crankshaft position sensor (POS) detects the actual engine speed and sends a signal to the ECM.
The ECM controls the electric throttle control actuator so that the engine speed coincides with the target value memorized in the ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ECM is determined by taking into consideration various engine conditions, such as during warming up, deceleration, and engine load (air conditioner, power steering and cooling fan operation, etc).
Note. If DTC P0507 is displayed with other DTC, first perform the trouble diagnosis for the other DTC.
The ECM controls the engine idle speed to a specified level through the fine adjustment of the air, which is let into the intake manifold, by operating the electric throttle control actuator. The operating of the throttle valve is varied to allow for optimum control of the engine idling speed. The crankshaft position sensor (POS) detects the actual engine speed and sends a signal to the ECM. The ECM controls the electric throttle control actuator so that the engine speed coincides with the target value memorized in the ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ECM is determined by taking into consideration various engine conditions, such as during warming up, deceleration, and engine load (air conditioner, power steering and cooling fan operation, etc.).
Power Steering Pressure (PSP) sensor is installed to the power steering high-pressure tube and detects a power steering load. This sensor is a potentiometer which transforms the power steering load into output voltage, and emits the voltage signal to the ECM. The ECM controls the ETC actuator and adjusts the throttle valve opening angle to increase the engine speed and adjusts the idle speed for the increased load.
The ECM consists of a microcomputer and connectors for signal input and output and for power supply.
Malfunction Indicator Lamp (MIL) is located on the instrument panel. When the ignition is turned on without engine running, MIL will light up. This is a bulb check. When the engine is started, MIL should go off. If MIL remains on, the on-board diagnostic system has detected an engine system malfunction.
Battery voltage is supplied to the ECM even when the ignition is turned off for the ECM memory function of the DTC memory, the air fuel ratio feedback compensation value memory, the idle air volume learning value memory, etc.
Intake Valve Timing (IVT) control solenoid valve is activated by on/off pulse duty (ratio) signals from the ECM. The IVT control solenoid valve changes the oil amount and direction of flow through IVT control unit or stops oil flow. The longer pulse width advances valve angle. The shorter pulse width retards valve angle. When on and off pulse widths become equal, the solenoid valve stops oil pressure flow to fix the intake valve angle at the control position.
The radiator coolant temperature sensor is installed on the radiator lower tank and is used to detect the radiator coolant temperature. The sensor modifies a voltage signal from the ECM and returns the modified signal to the ECM as the radiator coolant temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increase. The ECM uses this signal to control the cooling fan speed control solenoid valve.
Electric throttle control actuator consists of throttle control motor, acceleration pedal position sensor, throttle position sensor, etc. The throttle control motor is operated by the ECM, and it opens and closes the throttle valve. Accelerator pedal position sensor detects the accelerator pedal position, the opening and closing speed of the accelerator pedal, and feeds the voltage signals to the ECM. The ECM judges the current opening angle of the accelerator pedal from these signals and controls the throttle control motor based on these signals. The throttle position sensor detects the throttle valve position, and the opening and closing speed of the throttle valve, and feeds the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals, and the ECM controls the throttle control motor to make the throttle valve opening angle correct in response to driving condition.
Electric throttle control actuator consists of throttle control motor, acceleration pedal position sensor, throttle position sensor, etc. The throttle control motor is operated by the ECM, and it opens and closes the throttle valve. The current opening angle of the throttle valve is detected by the throttle position sensor and it provides the feedback to the ECM to control the throttle control motor to make the throttle valve opening angle correct in response to driving condition.
Power supply for the throttle control motor is provided to the ECM via throttle control motor relay. The throttle control motor relay is on/off controlled by the ECM. When the ignition switch is turned on, the ECM sends an on signal to throttle control motor relay and battery voltage is provided to the ECM. When the ignition switch is turned off, the ECM sends an off signal to throttle control motor relay and battery voltage is not provided to the ECM.
The throttle control motor is operated by the ECM and it opens and closes the throttle valve. The current opening angle of the throttle valve is detected by the throttle position sensor and it provides feedback to the ECM to control the throttle control motor to make the throttle valve opening angle correct in response to driving condition.
Intake Valve Timing (IVT) control position sensors are located in the front cylinder heads in both bank 1 and bank 2. This sensor uses a Hall integrated circuit (element). The cam position is determined by the intake primary cam sprocket concave (in 4 places). The ECM provides feedback to the IVT control for appropriate target valve open-close timing according to drive conditions based on detected cam position.
The front Heated Oxygen Sensors (HO2S) are located in each exhaust manifold, upstream of catalyst. They detect the amount of oxygen in the exhaust gas compared to the outside air. The front HO2S has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. The front HO2S signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from one volt to zero volts.
To judge the malfunction, the output from HO2S1 is monitored to determine whether the "rich" output is sufficiently high and whether the "lean" output is sufficiently low. When both the outputs are shifting to the lean side, the malfunction will be detected.
The front Heated Oxygen Sensors (HO2S) are located in each exhaust manifold, upstream of catalyst. They detect the amount of oxygen in the exhaust gas compared to the outside air. The front HO2S has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volts in leaner conditions. The front HO2S signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from one volt to zero volts.
To judge the malfunction, the output from HO2S1 is monitored to determine whether the "rich" output is sufficiently high and whether the "lean" output is sufficiently low. When both the outputs are shifting to the rich side, the malfunction will be detected.
The Heated Oxygen Sensor (HO2S2), after 3-way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Even if switching characteristics of the HO2S1 are shifted, the air-fuel ratio is controlled to stoichiometric, by the signal from the HO2S2. This sensor is made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volt in leaner conditions. Under normal conditions the HO2S2 is not used for engine control operation.
The HO2S2 has a much longer switching time between rich and lean than the HO2S1. The oxygen storage capacity before the 3-way catalyst (manifold) causes the longer switching time. To judge the malfunctions of HO2S2, ECM monitors whether the minimum voltage of sensor is sufficiently low during the various driving condition such as fuel-cut.
The Heated Oxygen Sensor (HO2S2), after 3-way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Even if switching characteristics of the HO2S1 are shifted, the air-fuel ratio is controlled to stoichiometric, by the signal from the HO2S2. This sensor is made of ceramic zirconia. The zirconia generates voltage from about one volt in richer conditions to zero volt in leaner conditions. Under normal conditions the HO2S2 is not used for engine control operation.
The HO2S2 has a much longer switching time between rich and lean than the HO2S1. The oxygen storage capacity before the 3-way catalyst (manifold) causes the longer switching time. To judge the malfunctions of HO2S2, ECM monitors whether the minimum voltage of sensor is sufficiently low during the various driving condition such as fuel-cut.
The malfunction information related to TCS control unit is transferred through the CAN communication line from VDC/TCS/ABS control unit to ECM. Be sure to erase the malfunction information such as DTC not only for VDC/TCS/ABS control unit but also for ECM after the TCS related repair.
This CAN communication line is used to control the smooth engine operation during the TCS operation. Pulse signals are exchanged between ECM and VDC/TCS/ABS control unit. Be sure to erase the malfunction information such as DTC not only in VDC/TCS/ABS control unit but also ECM after the TCS related repair.
This system controls the cooling fan operating speed. The opening of cooling fan speed control solenoid valve changes to control oil pressure provided to the cooling fan drive pump. This system consists of the cooling fan pump, cooling fan drive pump, cooling fan speed control solenoid valve, oil cooler, cooling fan fluid reservoir, etc.
The cooling fan pump is operated by the engine with the drive belts and provides oil pressure to the cooling fan drive pump which operates the cooling fan. The cooling fan speed control solenoid valve is installed between the cooling fan pump and cooling fan drive pump. The solenoid valve repeats on/off operation according to the signal sent from the ECM. The opening of the solenoid valve varies for optimum engine control. The optimum value stored in the ECM is determined by considering various engine conditions.
The ECM controls the cooling fan speed corresponding to the engine speed, the radiator coolant temperature, refrigerant pressure, vehicle speed, air conditioner switch signal, etc. The ECM determines the target fan speed based on the basic fan speed considering the radiator coolant temperature and the engine speed. The ECM controls fan speed between zero to 2550 RPM. When the cooling fan speed control solenoid valve is malfunctioning (does not operate), the cooling fan is operated at the maximum speed by engine through the drive belts.
The cooling fan speed control solenoid valve uses a on/off duty to control the pressure of the cooling fan fluid from the cooling fan pump. This solenoid valve is moved by on/off pulse from the ECM. The longer the on pulse is sent to the solenoid valve, the lower speed the cooling fan operates. If the cooling fan or another component in the cooling system malfunctions, engine coolant temperature will rise.
This system controls fuel pump operation. The amount of fuel flow delivered from the fuel pump is altered between 2 flow rates by the Fuel Pump Control Module (FPCM) operation. The FPCM determines the voltage supplied to the fuel pump (and therefore fuel flow).
Battery voltage is supplied to the fuel pump during the following conditions
- During engine cranking.
- When engine coolant temperature is less than 50°F (10°C).
- When engine is running under heavy load and high speed conditions.
About 8 volts is supplied to fuel pump during all other conditions.
The FPCM adjusts the voltage supplied to the fuel pump to control the amount of fuel flow. When the FPCM increases the voltage supplied to the fuel pump, the fuel flow is increased. When the FPCM decreases the voltage, the fuel flow is decreased.
Electric throttle control actuator consists of throttle control motor, acceleration pedal position sensor, throttle position sensor, etc. The throttle position sensor responds to the throttle valve movement. The throttle position sensor has 2 sensors. These sensors are a kind of potentiometer which transform the throttle valve position into output voltage, and emit the voltage signal to the ECM. In addition, these sensors detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle correct in response to driving condition. (Scheme 14)
Electric throttle control actuator consists of throttle control motor, acceleration pedal position sensor, throttle position sensor, etc. The throttle position sensor responds to the throttle valve movement. The throttle position sensor has 2 sensors. These sensors are a kind of potentiometer which transform the throttle valve position into output voltage, and emit the voltage signal to the ECM. In addition, these sensors detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle correct in response to driving condition. (Scheme 14)
When the malfunction is detected, ECM enters fail-safe mode and the MIL lights up. ECM stops the electric throttle control actuator control and throttle valve is maintained at a fixed opening (about 5 degrees) by the return spring.
This system controls flow rate of fuel vapor from the EVAP canister. The opening of the vapor by-pass passage in the EVAP Canister Purge Volume Control Valve (EVAP-CPVCV) changes to control the flow rate. The EVAP-CPVCV repeats ON/OFF operation according to the signal sent from the ECM. The opening of the valve varies for optimum engine control. The optimum value stored in the ECM is determined by considering various engine conditions. When the engine is operating, the flow rate of fuel vapor from the EVAP canister is regulated as the air flow changes.
The EVAP-CPVCV uses an ON/OFF duty to control the flow rate of fuel vapor from the EVAP canister. The EVAP-CPVCV is moved by ON/OFF pulses from the ECM. The longer the ON pulse, the greater the amount of fuel vapor that will flow through the valve.
The EVAP Canister Vent Control Valve (EVAP-CVCV) is located on the EVAP canister and is used to seal the canister vent. This solenoid valve responds to signals from the ECM. When the ECM sends an ON signal, the coil in the solenoid valve is energized. A plunger will then move to seal the canister vent. The ability to seal the vent is necessary for the on board diagnosis of other evaporative emission control system components. This solenoid valve is used only for diagnosis, and usually remains opened. When the vent is closed, under normal purge conditions, the evaporative emission control system is depressurized and allows "EVAP Control System (Small Leak)" diagnosis.
The EVAP Canister Vent Control Valve (EVAP-CVCV) is located on the EVAP canister and is used to seal the canister vent. This solenoid valve responds to signals from the ECM. When the ECM sends an ON signal, the coil in the solenoid valve is energized. A plunger will then move to seal the canister vent. The ability to seal the vent is necessary for the on board diagnosis of other evaporative emission control system components. This solenoid valve is used only for diagnosis, and usually remains opened. When the vent is closed, under normal purge conditions, the evaporative emission control system is depressurized and allows "EVAP Control System (Small Leak)" diagnosis.
The fuel level sensor is mounted in the fuel level sensor unit. The sensor detects a fuel level in the fuel tank and transmits a signal to the ECM. It consists of 2 parts, one is a mechanical float and the other side is a variable resistor. Fuel level sensor output voltage changes depending on the movement of the fuel mechanical float.
ECM receives 2 signals from the fuel level sensor. One is fuel level sensor power supply circuit, and the other is fuel level sensor ground circuit. This diagnosis indicates the latter to detect open circuit malfunction.
This system controls the cooling fan operating speed. The opening of cooling fan speed control solenoid valve changes to control oil pressure provided to the cooling fan drive pump. This system consists of the cooling fan pump, cooling fan drive pump, cooling fan speed control solenoid valve, oil cooler, cooling fan fluid reservoir, etc.
The cooling fan pump is operated by the engine with the drive belts and provides oil pressure to the cooling fan drive pump which operates the cooling fan. The cooling fan speed control solenoid valve is installed between the cooling fan pump and cooling fan drive pump. The solenoid valve repeats on/off operation according to the signal sent from the ECM. The opening of the solenoid valve varies for optimum engine control. The optimum value stored in the ECM is determined by considering various engine conditions.
The ECM controls the cooling fan speed corresponding to the engine speed, the radiator coolant temperature, refrigerant pressure, vehicle speed, air conditioner switch signal, etc. The ECM determines the target fan speed based on the basic fan speed considering the radiator coolant temperature and the engine speed. The ECM controls fan speed between zero to 2550 RPM. When the cooling fan speed control solenoid valve is malfunctioning (does not operate), the cooling fan is operated at the maximum speed by engine through the drive belts.
The cooling fan speed control solenoid valve uses a on/off duty to control the pressure of the cooling fan fluid from the cooling fan pump. This solenoid valve is moved by on/off pulse from the ECM. The longer the on pulse is sent to the solenoid valve, the lower speed the cooling fan operates. If the cooling fan or another component in the cooling system malfunctions, engine coolant temperature will rise.
The vacuum cut valve and vacuum cut valve by-pass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister. The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank. The vacuum cut valve by-pass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis. The vacuum cut valve by-pass valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then by-passed to apply intake manifold vacuum to the fuel tank.
The vacuum cut valve and vacuum cut valve by-pass valve are installed in parallel on the EVAP purge line between the fuel tank and the EVAP canister. The vacuum cut valve prevents the intake manifold vacuum from being applied to the fuel tank. The vacuum cut valve by-pass valve is a solenoid type valve and generally remains closed. It opens only for on board diagnosis. The vacuum cut valve by-pass valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the valve is opened. The vacuum cut valve is then by-passed to apply intake manifold vacuum to the fuel tank.
When the gear position is "P" or "N", Park/Neutral Position (PNP) switch is on. ECM detects position based on circuit continuity.
ECM receives 2 vehicle speed sensor signals via CAN communication line. One is sent from VDC/TCS/ABS control unit, and the other is from Transmission Control Module (TCM). ECM uses these 2 signals for engine control.
ECM receives current gear position signal, next gear position signal, shift change signal and shift pattern signal through CAN communication line from Transmission Control Module (TCM). ECM uses these 4 signals for engine control.
Brake switch signal is applied to the ECM through the stop lamp switch when the brake pedal is depressed. This signal is used mainly to decrease engine speed when vehicle is driving.
Electronic throttle control actuator consists of throttle control motor, Accelerator Pedal Position (APP) sensor, Throttle Position (TP) sensor, etc. APP sensor is connected to the accelerator pedal through the throttle drum and accelerator wire, and detects the accelerator pedal position by the throttle drum rotation angle.
APP sensor has 2 sensors. These sensors are a kind of potentiometers which transform the accelerator pedal position into output voltage, and emit the voltage signal to the ECM. (Scheme 15) In addition, these sensors detect the opening and closing speed of the accelerator pedal and feed the voltage signals to the ECM. The ECM judges the current opening angle of the accelerator pedal from these signals and controls the throttle control motor based on these signals.
Idle position of the accelerator pedal is determined by the ECM receiving the signal from the APP sensor. The ECM uses this signal for engine operation such as fuel cut.
Scheme 15
Controller Area Network (CAN) is a serial communication line for real time application. It is an on-vehicle multiplex communication line with high data communication speed and excellent error detection ability. Many electronic control units are equipped onto a vehicle, and each control unit shares information and links with other control units during operation (not independent). In CAN communication, control units are connected with 2 communication lines (CAN "H" line, CAN "L" line) allowing a high rate of information to be transmitted with less wiring. Each control unit transmits/receives data but selectively reads required data only.