Description
As part of an enhanced emissions test for inspection and maintenance, certain states require the status of System Readiness Test (SRT) be used to indicate whether the ECM has completed the self-diagnosis of major emission systems and components. Completion must be verified in order for the emissions inspection to proceed.
If a vehicle is rejected for a state emissions inspection due to one or more SRT items indicating INCMP, use this information to set the SRT to CMPLT.
In most cases the ECM will automatically complete its self-diagnosis cycle during normal usage, and the SRT status will indicate CMPLT for each application system. Once set as CMPLT, the SRT status remains CMPLT until the self-diagnosis memory is erased.
Occasionally, certain potions of the self-diagnostic test may not be completed as a result of the customer's normal driving pattern. The SRT will indicate INCMP for these items.
Accelerator pedal released position learning is an operation to learn the fully released position of the accelerator pedal by monitoring the Accelerator Pedal Position (APP) sensor output signal. It must be performed each time harness connector of APP 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.
Idle air volume learning is an operation to learn the idle air volume that keeps each engine within the specific range. It must be performed under any of the following conditions
- Each time electric throttle control actuator or ECM is replaced.
- Idle speed or ignition timing is out of specification.
Pre-Conditioning
Before proceeding, ensure the following conditions are met
- Battery voltage: more than 12.9 volts at idle.
- Engine coolant temperature: 158-203°F (70-95°C).
- Transmission: Park or Neutral.
- A/C, headlights, rear window defogger: off.
- Headlight switch: 1st position (only on vehicles with daytime running lights).
- Steering wheel: straight-ahead position.
- Vehicle speed: stopped.
- Transmission: warmed up. If using CONSULT-II on A/T-equipped vehicle, confirm FLUID TEMP SE in DATA MONITOR mode of A/T system indicates less than .9 volt. Or, drive vehicle for 10 minutes to warm up transmission.
The Intake Valve Timing (IVT) control system 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 camshaft timing control 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.
On 2.5L, the ECM performs on/off duty control of HO2S1 heaters based on engine speed and engine coolant temperature. The duty percent varies with engine coolant temperature when engine is started. On 3.5L, the ECM performs on/off control of HO2S1 heaters based on engine speed. On all models, HO2S1 heaters are turned off above 3600 RPM.
The ECM controls on/off operation of HO2S2 heaters based on engine speed. When engine speed is more than 3600 RPM, HO2S2 heaters are turned off. When engine speed is less than 3600 RPM after vehicle has been driven for 2 minutes at 43 MPH or more, HO2S2 heaters are turned on.
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 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 Absolute Pressure (AP) sensor is built into ECM. The sensor detects ambient barometric pressure and sends a voltage signal to the microcomputer.
The Intake Air Temperature (IAT) sensor (part of mass airflow 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 temperature increase.
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.
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.
The Intake Air Temperature (IAT) sensor (part of mass airflow 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 temperature increase.
The front Heated Oxygen Sensors (HO2S1) 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.
The front Heated Oxygen Sensors (HO2S1) 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 (HO2S1) 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.
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 voltage of sensor is unusually 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 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 or 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.
The ECM controls the cooling fan corresponding to the vehicle speed, engine coolant temperature, refrigerant pressure and A/C ON signal. The control system has 3-step control (high/low/off). (Scheme 1) The ECM controls cooling fan relays through the CAN communication line.
Scheme 1
Electric Throttle Control Actuator consists of throttle control motor, Throttle Position (TP) sensor, etc. The TP sensor responds to the throttle valve movement. The TP sensor has the 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 2) 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 properly in response to driving condition.
Scheme 2
The Accelerator Pedal Position (APP) sensor is installed on the upper end of the accelerator pedal assembly. The sensor detects the accelerator pedal position and sends a signal to the ECM.
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 3) 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 3
When a misfire occurs, engine speed will fluctuate. If the engine speed fluctuates enough to cause the Crankshaft Position (CKP) sensor (POS) signal to vary, ECM can detect a misfire. The misfire detection logic consists of the following two 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.
The Crankshaft Position (CKP) Sensor (POS) is located on the oil pan 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 retraction with intake valve camshaft 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 IC. 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 HO2S1 and HO2S2. A warm-up 3-way catalyst with high oxygen storage capacity will indicate a low switching frequency of HO2S2. As oxygen storage capacity decreases, HO2S2 switching frequency will increase. When the frequency ratio of HO2S1 and HO2S2 approaches a specified limit value, the warm-up 3-way catalyst malfunction is diagnosed.
In this 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 (EVAP-CPVCSV) is open to admit purge flow. Purge flow exposes the EVAP Control System Pressure Sensor (EVAP-CSPS) to intake manifold vacuum.
Under normal purge conditions (non-closed throttle), sensor output voltage indicates if pressure drop and purge flow are adequate. If not, a fault is determined.
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 (EVAP-CPVCSV), under the following "vacuum test" conditions.
The vacuum cut valve bypass valve is opened to clear the line between the fuel tank and the EVAP-CPVCSV. The EVAP Canister Vent Control Valve (EVAP-CVCV) will then be closed to shut the EVAP purge line off. The EVAP-CPVCSV is opened to depressurize the EVAP purge line using intake manifold vacuum. After this occurs, the EVAP-CPVCSV will be closed.
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 (EVAP-CPVCSV) changes to control the flow rate. The EVAP-CPVCSV 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-CPVCSV uses an ON/OFF duty to control the flow rate of fuel vapor from the EVAP canister. The EVAP-CPVCSV 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 (EVAP-CSPS) detects pressure in the purge line. The sensor output voltage to ECM increases as pressure increases. The EVAP-CSPS is not used for engine control. It is only used for on-board diagnosis.
The EVAP Control System Pressure Sensor (EVAP-CSPS) detects pressure in the purge line. The sensor output voltage to ECM increases as pressure increases. The EVAP-CSPS is not used for engine control. It is only used for on-board diagnosis.
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 (EVAP-CPVCSV).
This diagnosis detects very small leaks in the EVAP purge line between the fuel tank and EVAP Canister Purge Volume Control Solenoid Valve (EVAP-CPVCSV) using engine intake manifold vacuum. If ECM detects a very small leak, DTC P0456 will set. If ECM detects a small leak, DTC P0442 will set.
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 mechanical float and the other side is 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 mechanical float and the other side is 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 mechanical float and the other side is 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 indicates the former, to detect open or short circuit malfunction.
The Vehicle Speed Sensor (VSS) is installed in the transaxle. It contains a pulse generator which provides a vehicle speed signal to the instrument cluster. The instrument cluster then sends a signal to the ECM through 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).
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 connector 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.
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.
Intake Valve Timing Control (IVTC) solenoid valve is activated by on/off pulse duty (ratio) signals from the ECM. The IVTC solenoid valve changes the oil amount and direction of flow through IVTC 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.
Electric throttle control actuator consists of throttle control motor, Throttle Position (TP) sensor, etc. The throttle control motor is operated by the ECM, and it opens and closes the throttle valve. The TP sensor detects the throttle valve position, 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 properly in response to driving condition.
Electric throttle control actuator consists of throttle control motor, 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 properly 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 (TP) sensor, and it provides feedback to the ECM to control the throttle control motor to make the throttle valve opening angle properly in response to driving condition.
The front Heated Oxygen Sensors (HO2S1) 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 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 (HO2S1) 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 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.
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 low 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 maximum voltage of sensor is sufficiently high during the various driving condition such as fuel-cut.
The malfunction information related to ABS or ABS/TCS is transferred through the CAN communication line from ABS actuator and electric unit to ECM. Be sure to erase the malfunction information such as DTC not only for ABS actuator and electric unit but also for ECM after the ABS or ABS/TCS related repair.
This CAN communication line is used to control the smooth engine operation during the ABS or TCS operation. Pulse signals are exchanged between ECM and ABS actuator and electric unit. Be sure to erase the malfunction information such as DTC not only in ABS actuator and electric unit but also ECM after the ABS or ABS/TCS related repair.
The ECM controls the cooling fan corresponding to the vehicle speed, engine coolant temperature, refrigerant pressure and A/C ON signal. The control system has 3-step control (high/low/off). (Scheme 1) The ECM controls cooling fan relays through the CAN communication line.
Electric Throttle Control Actuator consists of throttle control motor, Throttle Position (TP) sensor, etc. The TP sensor responds to the throttle valve movement. The TP sensor has the 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 2) 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 properly in response to driving condition.
Electric Throttle Control Actuator consists of throttle control motor, Throttle Position (TP) sensor, etc. The TP sensor responds to the throttle valve movement. The TP sensor has the 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 2) 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 properly in response to driving condition.
Electric Throttle Control Actuator consists of throttle control motor, Throttle Position (TP) sensor, etc. The TP sensor responds to the throttle valve movement. The TP sensor has the 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 2) 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 properly in response to driving condition.
The Accelerator Pedal Position (APP) sensor is installed on the upper end of the accelerator pedal assembly. The sensor detects the accelerator pedal position and sends a signal to the ECM.
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 3) 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.
This diagnosis detects leaks in the EVAP purge line using vapor pressure in the fuel tank. The EVAP Canister Vent Control Valve (EVAP-CVCV) is closed to shut the EVAP purge line. The vacuum cut valve bypass valve will then be opened to clear the line between the fuel tank and the EVAP Canister Purge Volume Control Solenoid Valve (EVAP-CPVCSV). The EVAP Control System Pressure Sensor (EVAP-CSPS) 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-CPVCSV.
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 (EVAP-CPVCSV) changes to control the flow rate. The EVAP-CPVCSV 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-CPVCSV uses an ON/OFF duty to control the flow rate of fuel vapor from the EVAP canister. The EVAP-CPVCSV 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.
This diagnosis detects very small leaks in the EVAP line between fuel tank and EVAP Canister Purge Volume Control Solenoid Valve (EVAP-CPVCSV), using vapor pressure in the fuel tank. The EVAP Canister Vent Control Valve (EVAP-CVCV) is closed to shut the EVAP purge line. The vacuum cut valve bypass valve will then be opened to clear the line between the fuel tank and the EVAP-CPVCSV. The EVAP Control System Pressure Sensor (EVAP-CSPS) 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-CPVCSV.
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 mechanical float and the other side is 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.
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.
ASCD steering switch has variant values of electrical resistance for each button. ECM reads voltage variation of switch, and determines which button is operated.
When the brake pedal is depressed, ASCD brake switch is turned off and stop lamp switch is turned on. ECM detects the state of the brake pedal by this input.
ECM receives vehicle speed signals via 2 different lines, and detects vehicle speed for ASCD control. Vehicle speed signals are input from instrument cluster and Transmission Control Module (TCM) separately. Signal from TCM is via CAN communication line.
When the gear position is "P" (A/T models only) or "N", Park/Neutral Position (PNP) switch is on. ECM detects the position because the continuity of the line (the "on" signal) exists.
When the engine is running at low or medium speed, the power valve is fully closed. Under this condition, the effective suction port length is equivalent to the total length of the intake manifold collector's suction port including the intake valve. This long suction port provides increased air intake which results in improved suction efficiency and higher torque generation.
The surge tank and one-way valve are provided. When engine is running at high speed, the ECM sends the signal to the Variable Induction Air Control System (VIAS) control solenoid valve. This signal introduces the intake manifold vacuum into the power valve actuator and therefore opens the power valve to two suction passages together in the collector.
Under this condition, the effective port length is equivalent to the length of the suction port provided independently for each cylinder. This shortened port length results in enhanced engine output with reduced suction resistance under high speeds.
The power valve is installed in intake manifold collector and used to control the suction passage of the variable induction air control system. It is set in the fully closed or fully opened position by the power valve actuator operated by the vacuum stored in the surge tank. The vacuum in the surge tank is controlled by the VIAS control solenoid valve.
The VIAS control solenoid valve cuts the intake manifold vacuum signal for power valve control. It responds to on/off signals from the ECM. When the solenoid valve is off, the vacuum signal from the intake manifold is cut. When the ECM sends an on signal, the coil pulls the plunger downward and feeds the vacuum signal to the power valve actuator.
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 the engine speed when the vehicle is driving.
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 transmission with less wiring. Each control unit transmits/receives data but selectively reads required data only.