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Advanced Diagnostics: Overview Honda Element YH2 рестайлинг

Testing & Diagnostics 1 illustration ~20558 words

Identifying Variable Valve Timing Control (VTC) System Consisting Components With Flow Diagram. Scheme 1

Scheme 1: Identifying Variable Valve Timing Control (VTC) System Consisting Components With Flow Diagram

General Description

The variable valve timing control (VTC) system controls the timing of the intake camshaft. It uses hydraulic pressure to operate the VTC actuator so the valve timing is optimized depending on driving conditions. The engine control module (ECM)/powertrain control module (PCM) monitors the phase control command and the actual timing of the camshaft by using camshaft position (CMP) sensor A. If the phase difference between them is excessive for a certain time period, a malfunction is detected and a DTC is stored.

The mass airflow (MAF) sensor directly measures the amount of intake airflow into the engine, and the engine control module (ECM)/powertrain control module (PCM) controls the fuel injection based on the measured value. The manifold absolute pressure (MAP) sensor measures the intake manifold pressure and the ECM/PCM calculates the amount of intake airflow from the MAP sensor output and the engine revolutions. The ECM/PCM compares the MAF sensor output (amount of intake airflow) and the amount of intake airflow calculated from MAP sensor output. If their difference is too large (in the malfunction area), the ECM/PCM detects a malfunction and a DTC is stored.

The mass airflow (MAF) sensor is attached to the intake air passage, and it measures the amount of intake airflow. The MAF sensor is a hot wire airflow meter. The airflow cools the electrically heated wire that is mounted in the air passage. The engine control module (ECM)/powertrain control module (PCM) determines the amount of intake airflow by detecting the current that is required to keep the hot wire at a constant temperature. The lower limit of the MAF sensor output is specified. If the output is below that limit, the ECM/PCM detects a malfunction and stores a DTC.

The mass airflow (MAF) sensor is attached to the intake air passage, and it measures the amount of intake airflow. The MAF sensor is a hot wire airflow meter. The airflow cools the electrically heated wire that is mounted in the air passage. The engine control module (ECM)/powertrain control module (PCM) determines the amount of intake airflow by detecting the current that is required to keep the hot wire at a constant temperature. The upper limit of the MAF sensor output is specified. If the output is above that limit, the ECM/PCM detects a malfunction and stores a DTC.

If a signal voltage from the MAP sensor is a set value or less, the engine control module (ECM)/powertrain control module (PCM) detects a malfunction and a DTC is stored.

The manifold absolute pressure (MAP) sensor senses manifold absolute pressure (vacuum) and converts it into electrical signals. The MAP sensor outputs low signal voltage at high-vacuum (throttle valve closed) and high signal voltage at low-vacuum (throttle valve wide open). If a signal voltage from the MAP sensor is a set value or more, the engine control module (ECM)/powertrain control module (PCM) detects a malfunction and a DTC is stored.

Two engine coolant temperature sensors and one intake air temperature sensor are used by the engine control module (ECM)/powertrain control module (PCM).

When the engine is stopped and enough time has passed, the temperature of the engine will equal the ambient temperature. When an inappropriate temperature is detected after comparing the temperature readings of each sensor, a malfunction in the corresponding sensor is detected and a DTC is stored.

The intake air temperature (IAT) sensor is a thermistor that detects intake air temperature, and it is used for A/F feedback control to compensate for the atmospheric density fluctuations that accompany changes in intake air temperature.

The IAT sensor resistance varies depending on temperature. The output voltage and the sensor resistance increase as the intake air temperature decreases. Conversely, the output voltage and the sensor resistance decrease as the intake air temperature increases. If the IAT sensor output voltage is excessively low, the engine control module (ECM)/powertrain control module (PCM) detects a malfunction and a DTC is stored.

The IAT sensor resistance varies depending on temperature. The output voltage and the sensor resistance increase as the intake air temperature decreases. Conversely, the output voltage and the sensor resistance decrease as the intake air temperature increases. If the IAT sensor output voltage is excessively high, the engine control module (ECM)/powertrain control module (PCM) detects a malfunction and a DTC is stored.

The engine control module (ECM)/powertrain control module (PCM) supplies voltage to the engine coolant temperature (ECT) signal circuit (about 5 V) through a pull-up resistor. As the engine coolant cools, ECT sensor 1 resistance increases, and the ECM/PCM detects a high signal voltage. As the engine coolant warms, ECT sensor 1 resistance decreases, and the ECM/PCM detects a low signal voltage.

If the ECT sensor 1 output voltage after driving a set time after starting the engine does not reach a set temperature, or when the difference between the ECT sensor 1 output voltage when driving and the output voltage of the ECT sensor 1 after the engine is stopped a set time does not change a certain amount, a malfunction is detected and a DTC is stored.

Engine coolant temperature (ECT) sensor 1 is used for air/fuel ratio feedback control, ignition timing control, idle speed control, and other functions. The ECT sensor 1 resistance varies depending on the engine coolant temperature. As the engine coolant cools, the ECT sensor 1 resistance increases, and the engine control module (ECM)/powertrain control module (PCM) detects a high signal voltage. As the engine coolant warms, the ECT sensor 1 resistance decreases, and the ECM/PCM detects a low signal voltage. If the ECT sensor 1 output voltage is less than a set value when the engine coolant temperature is high, the ECM/PCM detects a malfunction and a DTC is stored.

Engine coolant temperature (ECT) sensor 1 is used for air/fuel ratio feedback control, ignition timing control, idle speed control, and other functions. The ECT sensor 1 resistance varies depending on the engine coolant temperature. As the engine coolant cools, the ECT sensor 1 resistance increases, and the engine control module (ECM)/powertrain control module (PCM) detects a high signal voltage. As the engine coolant warms, the ECT sensor 1 resistance decreases, and the ECM/PCM detects a low signal voltage. If the ECT sensor 1 output voltage is more than a set value when the engine coolant temperature is low, the ECM/PCM detects a malfunction and a DTC is stored.

Throttle position (TP) sensor A is a semiconductor type, and it is attached to the throttle body and shaft to determine throttle valve position.

The throttle valve position signal from TP sensor A is transmitted to the throttle actuator control module for target position feedback control, then to the engine control module (ECM)/powertrain control module (PCM) as an actual throttle valve position signal.

If the signal from TP sensor A is a fixed value or less for a set time, the throttle actuator control module detects a malfunction and sends the malfunction data to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a TP sensor A malfunction and stores a DTC.

Throttle position (TP) sensor A is a semiconductor type, and it is attached to the throttle body and shaft to determine throttle valve position.

If the signal from TP sensor A is a fixed value or more for a set time, the throttle actuator control module detects a malfunction and sends the malfunction data to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a TP sensor A malfunction and stores a DTC.

The engine control module (ECM)/powertrain control module (PCM) supplies voltage to the engine coolant temperature (ECT) signal circuit (about 5 V) through a pull-up resistor. As the engine coolant cools, the ECT sensor 1 resistance increases, and the ECM/PCM detects a high signal voltage. As the engine coolant warms, the ECT sensor 1 resistance decreases, and the ECM/PCM detects a low signal voltage.

If the ECT sensor 1 output voltage does not reach a specified temperature at which closed-loop control for stoichiometric air/fuel ratio starts within a set time, depending on the initial coolant temperature after starting the engine, the ECM/PCM detects a malfunction and a DTC is stored.

The thermostat is closed when the engine coolant temperature is low, and it stops the circulation of engine coolant to speed engine warm up. When the engine coolant temperature increases, the thermostat opens and circulates engine coolant to control its temperature. When the engine coolant temperature decreases, the opening area of the thermostat is reduced to regulate the engine coolant temperature. If the thermostat sticks open, engine warm up is delayed, and exhaust emissions are adversely affected. The engine control module (ECM)/powertrain control module (PCM) measures the rise in the coolant temperature after the engine starts at the engine block and at the radiator, and it estimates the characteristics of the engine coolant temperature by calculations based on those two temperatures and the driving conditions. When ECT 2 immediately increases from the starting value, it is defined as the thermostat stuck open. When ECT 2 does not increase to the specified value, it is defined as a thermostat malfunction.

The air/fuel ratio (A/F) sensor has a linear signal output in relation to the oxygen concentration. The engine control module (ECM)/powertrain control module (PCM) computes the air/fuel ratio from the A/F sensor output voltage and uses fuel feedback control to improve exhaust emissions. The ECM/PCM measures the response characteristics against the A/F sensor output, and if the average inversion cycle time is less than the specified value, it detects a deteriorated response and stores a DTC.

The air/fuel ratio (A/F) sensor is activated by warming the element with a heater to maintain it at a steady high temperature for accurate air/fuel (A/F) ratio calculation. The A/F sensor does not become active when the element is not properly heated due to a heater malfunction, and the exhaust emissions deteriorate. The engine control module (ECM)/powertrain control module (PCM) monitors the A/F sensor condition by monitoring the A/F sensor internal resistance.

When the A/F sensor does not activate in a set time after the A/F sensor heater is turned on (with high A/F sensor internal resistance), a malfunction of the A/F sensor heater is detected, and a DTC is stored.
The A/F sensor heater cycles ON and OFF within a set time. The heater's state is detected by monitoring the internal resistance of the A/F sensor. If the resistance remains high when the heater is ON, a malfunction in the A/F sensor heater is detected, and a DTC is stored. Because the degree of effect on engine control differs according to the A/F sensor internal resistance, there are two malfunction detection threshold levels. When either one is reached, a malfunction is detected.

A heater for the sensor element is embedded in the air/fuel ratio (A/F) sensor (sensor 1), and it is controlled by the engine control module (ECM)/powertrain control module (PCM). It is activated and heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature is cold.

If the A/F sensor (sensor 1) heater current is not a set value, or the heater is overheated, a malfunction is detected and a DTC is stored.

The secondary heated oxygen sensor (HO2S) (sensor 2) detects the oxygen content in the exhaust gas downstream of the three way catalytic converter (TWC) during stoichiometric air/fuel ratio feedback control based on the air/fuel ratio (A/F) sensor (sensor 1) output voltage. The secondary HO2S controls the air/fuel ratio from the A/F sensor output voltage so that the

TWC efficiency is optimized.

After current is applied to the secondary HO2S heater, if the secondary HO2S output continues low (lean) during feedback control, a malfunction is detected and a DTC is stored.

After current is applied to the secondary HO2S heater, if the secondary HO2S output continues high (rich) exceeding the upper limit used during feedback control, a malfunction is detected and a DTC is stored.

The secondary heated oxygen sensor (HO2S) (sensor 2) detects the oxygen content in the exhaust gas downstream of the three way catalytic converter (TWC) during stoichiometric air/fuel ratio feedback control. The secondary HO2S controls the air/fuel ratio with the A/F sensor output voltage to optimize TWC efficiency.

If the response time of the secondary HO2S becomes longer than the specified time after current to the secondary HO2S heater is applied, a malfunction is detected and a DTC is stored.

A heater for the zirconia element is embedded in the secondary heated oxygen sensor (secondary HO2S), and it is controlled by the engine control module (ECM)/powertrain control module (PCM). When activated, it heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature is cold.

If the secondary HO2S heater draws other than a specified amperage, the ECM/PCM detects a malfunction and a DTC is stored.

Long term fuel trim is computed from short term fuel trim and is used to regulate long term deviation from the stoichiometric air/fuel ratio, which occurs when fuel metering components deteriorate with age or system failures occur. In addition, long term fuel trim is stored in the ECM/PCM memory and is used to determine when fuel metering components malfunction.

When long term fuel trim is higher than normal, which is about 1.0 (0 %), the amount of injected fuel must be increased, and when lower than normal, it must be decreased. If long term fuel trim is higher than normal (too lean), a malfunction in the fuel metering components is detected and a DTC is stored.

The engine control module (ECM)/powertrain control module (PCM) detects the oxygen content in the exhaust gas from the air/fuel ratio (A/F) sensor (sensor 1) signal voltage, and it uses fuel feedback control to maintain the optimal air/fuel ratio. The air/fuel ratio coefficient for correcting the amount of injected fuel is the short term fuel trim. The ECM/PCM varies short term fuel trim continuously to keep the air/fuel ratio close to the stoichiometric ratio for all driving conditions. Long term fuel trim is computed from short term fuel trim and is used to regulate long term deviation from the stoichiometric air/fuel ratio, which occurs when fuel metering components deteriorate with age or system failures occur. In addition, long term fuel trim is stored in the ECM/PCM memory and is used to determine when fuel metering components malfunction. When long term fuel trim is higher than normal, which is about 1.0 (0 %), the amount of injected fuel must be increased, and when lower than normal, it must be decreased. If long term fuel trim is lower than normal (too rich), a malfunction in the fuel metering components is detected and a DTC is stored.

Throttle position (TP) sensor B is a semiconductor type, and it is attached to the throttle body and shaft to determine throttle valve position.

The throttle valve position signal from TP sensor B is transmitted to the throttle actuator control module for target position feedback control, then to the engine control module (ECM)/powertrain control module (PCM) as an actual throttle valve position signal.

If the signal from TP sensor B is a fixed value or less for a set time, the throttle actuator control module detects a malfunction and sends the malfunction data to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a TP sensor B malfunction and stores a DTC.

Throttle position (TP) sensor B is a semiconductor type, and it is attached to the throttle body and shaft to determine throttle valve position.

If the signal from TP sensor B is a fixed value or more for a set time, the throttle actuator control module detects a malfunction and sends the malfunction data to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a TP sensor B malfunction and stores a DTC.

The crankshaft vibrates slightly when each cylinder fires. If a misfire occurs, the crankshaft rotation speed changes rapidly. The engine control module (ECM)/powertrain control module (PCM) monitors the crankshaft rotation speed based on the output pulses from the crankshaft position (CKP) sensor. By monitoring changes in the crankshaft rotation speed, the ECM/PCM counts the number of misfires and determines which cylinder is misfiring. If more than one DTC from P0301 through P0304 has been stored while misfires in multiple cylinders are detected, a malfunction is detected and a DTC is stored.

There are two types of misfire detection.

Type 1 (1 drive cycle): When the number of misfires per 200 engine revolutions reaches the level that damages the three way catalyst (TWC), a DTC is stored and the MIL blinks. When the misfire ceases, the MIL remains on steady instead of blinking.

Type 2 (2 drive cycles): When the number of misfires per 1,000 engine revolutions reaches the level that affects FTP mode exhaust emissions, a DTC is stored and the MIL comes on.

There are two types of misfire detection.

Type 2 (2 drive cycles): When the number of misfires per 1,000 engine revolutions reaches the level that affects FTP mode exhaust emissions, a DTC is stored and the MIL comes on.

The knock sensor is mounted on the engine block and detects engine knocking. The vibrations caused by the knocking are converted into electrical signals through the piezo ceramic element. The engine control module (ECM)/powertrain control module (PCM) controls the ignition timing based on the electrical signals. If the signals from the knock sensor do not vary for a set time, the ECM/PCM detects a malfunction and stores a DTC.

The crankshaft position (CKP) sensor consists of a rotor and a semiconductor that detects rotor position. When the engine starts, the rotor turns and the magnetic flux in the semiconductor device changes. The changes of magnetic flux are converted into pulsing signals to the engine control module (ECM)/powertrain control module (PCM). The CKP sensor detects injection/ignition timing for each cylinder and engine speed.

If no pulsing signals from the CKP sensor are detected, a malfunction is detected and a DTC is stored.

If an abnormal amount of pulsing signals from the CKP sensor are detected, a malfunction is detected and a DTC is stored.

Camshaft position (CMP) sensor A detects the intake camshaft timing and sends pulsing signals to the engine control module (ECM)/powertrain control module (PCM). The ECM/PCM determines the advance or the retard of the camshaft timing according to the signals from the crankshaft position (CKP) sensor and CMP sensor A. If the pulse deviates from a set range over a specified time period while the variable valve timing control (VTC) is not activated, or the timing of the camshaft deviates from a set range over a specified time period while the engine is running with the VTC activated, a malfunction is detected and a DTC is stored.

Camshaft position (CMP) sensor A detects the intake camshaft timing and sends pulsing signals to the engine control module (ECM)/powertrain control module (PCM). The ECM/PCM determines the advance or the retard of the camshaft timing according to the signals from the crankshaft position (CKP) sensor and CMP sensor A. If the number of pulsing signals from CMP sensor A during intervals between the CKP standard pulses is more or less than the proper number, a malfunction is detected and a DTC is stored.

The camshaft position (CMP) sensor B consists of a rotor and a semiconductor that detects rotor position. When the rotor turns after starting the engine, the changes of magnetic flux in the semiconductor are converted into pulsing signals to the engine control module (ECM)/powertrain control module (PCM). The CMP sensor B detects the top dead center of each cylinder for fuel injection timing.

If CMP sensor B pulsing signals are detected an abnormal number of times due to noise, a malfunction is detected and a DTC is stored.

The three way catalytic converter (TWC) converts hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to water vapor, carbon dioxide (CO2), and dinitrogen (N2).

The TWC efficiency does not depend entirely on engine conditions or the deterioration level of the TWC. It can be optimized by stabilizing the secondary HO2S output.

If the TWC deteriorates, the air/fuel ratio downstream of the TWC (the secondary HO2S output) often differs from the target secondary HO2S output, and the status is represented by the parameter (SIGSQRLS).

Therefore, if the SIGSQRLS exceeds a specified value for a set time, a malfunction is detected and a DTC is stored.

The evaporative emission (EVAP) canister purge valve is attached to the vacuum port between the EVAP canister and the intake manifold. The engine control module (ECM)/powertrain control module (PCM) does not turn on the EVAP canister purge valve when the engine coolant temperature is 131 °F (55 °C) or less. The ECM/PCM adjusts the amount of fuel vapor sent to the engine by controlling the EVAP canister purge valve duty cycle.

When the return signal does not change according to the EVAP canister purge valve output for a set time, the ECM/PCM detects a malfunction, and a DTC is stored.

The fuel tank pressure (FTP) sensor is installed on the evaporative emission (EVAP) canister. The FTP sensor is used to detect leaks in the EVAP system. The engine control module (ECM)/powertrain control module (PCM) monitors the FTP sensor output voltage. The FTP sensor output voltage rises as the fuel tank pressure increases. Conversely, the FTP sensor output voltage drops as the fuel tank pressure decreases. Rapid changes in the FTP sensor output voltage due to electrical noise or an intermittent open during the EVAP leak detection may cause incorrect leak detection, so abnormal output is monitored.

If the FTP sensor output voltage changes a specified number of times within a set time, the ECM/PCM detects a malfunction and stores a DTC.

The fuel tank pressure (FTP) sensor is installed on the evaporative emission (EVAP) canister and detects the fuel tank pressure. The FTP sensor is used to detect leaks in the EVAP system.

The engine control module (ECM)/powertrain control module (PCM) monitors the FTP sensor output voltage. The FTP sensor output voltage rises as the fuel tank pressure increases. Conversely, the FTP sensor output voltage drops as the fuel tank pressure decreases. If the FTP sensor output voltage does not reach a target value within a set time after starting the engine in a cold condition, the ECM/PCM detects a malfunction and stores a DTC.

The fuel tank pressure (FTP) sensor is installed on the evaporative emission (EVAP) canister and detects the fuel tank pressure. The FTP sensor is used to detect leaks in the EVAP system.

The engine control module (ECM)/powertrain control module (PCM) monitors the FTP sensor output voltage. The FTP sensor output voltage rises as the fuel tank pressure increases. Conversely, the FTP sensor output voltage drops as the fuel tank pressure decreases. If the FTP sensor output voltage is higher than a target value for a set time after starting the engine in a cold condition, the ECM/PCM detects a malfunction and stores a DTC.

The evaporative emission (EVAP) leak detection system uses an engine off natural vacuum (EONV) method. The EONV method detects leakage from the change in fuel tank pressure via the fuel tank pressure (FTP) sensor with the engine off.

Here is an overview of the malfunction detection for the EONV method

Step 1: Judgement of detection of 0.09 inch leak as normal operation

Step 2: Judgement of detection of 0.02 inch leak as normal operation

Step 3: Detection of 0.02 inch leak

Step 4: Detection of atmospheric air open failure

Step 5: Flickering of the FTP sensor

< Step 1, 2 and 3 proceed simultaneously. Step 4 and 5 proceed simultaneously. >

Step 1

After the engine has stopped, the engine control module (ECM)/powertrain control module (PCM) monitors the variation of the FTP sensor output to detect "no 0.09 inch leak" depending on the variation corresponding to the pressure inside the fuel tank.

If the variation corresponding to the pressure is less than a specified value and continues for a specified duration, it is identified as a malfunction of "0.09 inch leak" and the diagnosis completes.
If the variation corresponding to pressure is more than a specified value before a specified duration has passed, it is defined as "no 0.09 inch leak", judgement of detection of a 0.09 inch leak is completed, and goes to 0.02 inch leak monitor.

Step 2

After the engine has stopped, the ECM/PCM monitors the variation of the FTP sensor output to detect "no 0.02 inch leak" depending on the variation corresponding to the increasing pressure inside the fuel tank.

If "no 0.02 inch leak" is detected, it is identified as normal; the diagnosis is complete.
If the pressure inside the fuel tank does not increase for a specified value or more within a specified duration, goes to step 3.

Step 3

The ECM/PCM continues to monitor the FTP sensor output to detect "no 0.02 inch leak" depending on the variation corresponding to the decreasing pressure inside the fuel tank. until the detection completes.

If a "0.02 inch leak" is detected, it is identified as a malfunction; the diagnosis is complete.
If "no leakage" is detected, it is identified as normal; the diagnosis is complete.
If the pressure is not atmospheric pressure or less when the detection is completed, reserve identification and the diagnosis is complete.

Step 4

After the engine has stopped, the ECM/PCM monitors the variation of the FTP sensor output to detect atmospheric air failure, after keeping the canister vent opened for a specified duration to stabilize the pressure inside the fuel tank.

If the pressure inside the fuel tank after a specified duration has passed deviated exceeding a specified value from the sensor zero point, and if oil is not identified to fuel during EONV is performed, atmospheric air open failure is detected.

Step 5

After the engine has stopped, the ECM/PCM monitors the variation of the FTP sensor output to detect FTP sensor flickering failure, after keeping the canister vent opened for a specified duration to stabilize the pressure inside the fuel tank.

If the deviation of pressure inside the fuel tank and an average value after a specified duration has passed exceeded a specified value for more than a specified duration, failure of FTP sensor flickering is detected.

Here is an overview of the malfunction detection for the EONV method

Step 1: Judgement of detection of 0.09 inch leak as normal operation

Step 2: Judgement of detection of 0.02 inch leak as normal operation

Step 3: Detection of 0.02 inch leak

Step 4: Detection of atmospheric air open failure

Step 5: Flickering of the FTP sensor

< Step 1, 2 and 3 proceed simultaneously. Step 4 and 5 proceed simultaneously. >

Step 1

If the variation corresponding to the pressure is less than a specified value and continues for a specified duration, it is identified as a malfunction of "0.09 inch leak" and the diagnosis completes.
If the variation corresponding to pressure is more than a specified value before a specified duration has passed, it is defined as "no 0.09 inch leak", judgement of detection of a 0.09 inch leak is completed, and goes to 0.02 inch leak monitor.

Step 2

If "no 0.02 inch leak" is detected, it is identified as normal; the diagnosis is complete.
If the pressure inside the fuel tank does not increase for a specified value or more within a specified duration, goes to step 3.

Step 3

If a "0.02 inch leak" is detected, it is identified as a malfunction; the diagnosis is complete.
If "no leakage" is detected, it is identified as normal; the diagnosis is complete.
If the pressure is not atmospheric pressure or less when the detection is completed, reserve identification and the diagnosis is complete.

Step 4

If the pressure inside the fuel tank after a specified duration has passed deviated exceeding a specified value from the sensor zero point, and if oil is not identified to fuel during EONV is performed, atmospheric air open failure is detected.

Step 5

If the deviation of pressure inside the fuel tank and an average value after a specified duration has passed exceeded a specified value for more than a specified duration, failure of FTP sensor flickering is detected.

When the fuel fill cap is installed properly, and the purge flow increases, there is some normal resistance to airflow through the evaporative emission (EVAP) canister, and the fuel tank pressure (FTP) sensor value drops as expected.

If the fuel fill cap is loose, and the purge flow increases, there is less resistance to airflow through the system because air is drawn into the fuel tank from the atmosphere, and the FTP sensor value does not drop as expected.

Based on these characteristics, the engine control module (ECM)/powertrain control module (PCM) looks at the relationship between purge flow and fuel tank pressure, and when the fuel tank pressure decreases very little as the purge flow increases, a loose fuel cap is detected.

< Above failure detection is normally operated during purge >

The fuel level sensor is incorporated with the fuel pump and installed in the fuel tank. Using a built-in potentiometer and float, it converts the movement of the float into electrical signals that correspond to the fuel level, and it indicates the amount of fuel in the fuel tank. If the engine control module (ECM)/powertrain control module (PCM) receives no change in the fuel level sensor output after driving for a specified number of miles, it detects a malfunction and stores a DTC.

The fuel level sensor (fuel gauge sending unit) is incorporated into the fuel pump and installed in the fuel tank. Using a built-in potentiometer and float, it converts the movement of the float to electrical signals as an output that corresponds to fuel level variations in the fuel tank. The fuel level, which is indicated by the gauge control module, is sent to the engine control module (ECM)/powertrain control module (PCM) via the controller area network (CAN). If the ECM/PCM detects a signal from the fuel level sensor (fuel gauge sending unit) below a predetermined value for a set time or more, it detects a malfunction and stores a DTC.

The fuel level sensor (fuel gauge sending unit) is incorporated into the fuel pump and installed in the fuel tank. Using a built-in potentiometer and float, it converts the movement of the float to electrical signals as an output that corresponds to fuel level variations in the fuel tank. The fuel level, which is indicated by the gauge control module, is sent to the engine control module (ECM)/powertrain control module (PCM) via the controller area network (CAN). If the ECM/PCM detects a signal from the fuel level sensor (fuel gauge sending unit) above a predetermined value for a set time or more, it detects a malfunction and stores a DTC.

The fuel (vapor) vaporized in the fuel tank is stored in the canister temporarily and introduced in the engine through the evaporative emission (EVAP) canister purge valve. The engine control module (ECM)/powertrain control module (PCM) controls the vapor amount introduced in the engine by repeating switching the power of the EVAP canister purge valve at a constant frequency according to the condition of the engine.

< STEP 1 >

The EVAP canister purge valve drives normally (EVAP canister purge valve OPEN OK) and detects that the purge flow is normal when the pulse of the EVAP canister purge valve drive cycle is transmitted to fuel tank pressure (FTP) sensor by the purge flow (pulse method).

OK determination: Pulse exists (P145C OK)

P0497 Purge flow OK
P0496 EVAP canister purge valve Open fix OK

NG determination: No pulse (P145C NG)

Either purge flow P0497 abnormality or P0496 EVAP canister purge valve OPEN failure.
In this case, classify the failure part according to < STEP 2 >.

< STEP 2 >

In case there is no pulse, it is determined either no purge flow or EVAP canister purge valve OPEN fix as follows

When the FTP sensor fluctuates from negative pressure condition to atmospheric pressure side after the ignition is turned off: P0496 EVAP canister purge valve OPEN fix

When there is no fluctuation of the FTP sensor: P0497 purge flow NG

< STEP 1 >

OK determination: Pulse exists (P145C OK)

P0497 Purge flow OK
P0496 EVAP canister purge valve Open fix OK

NG determination: No pulse (P145C NG)

Either purge flow P0497 abnormality or P0496 EVAP canister purge valve OPEN failure.
In this case, classify the failure part according to < STEP 2 >.

< STEP 2 >

In case there is no pulse, it is determined either no purge flow or EVAP canister purge valve OPEN fix as follows

When the FTP sensor fluctuates from negative pressure condition to atmospheric pressure side after the ignition is turned off: P0496 EVAP canister purge valve OPEN fix

When there is no fluctuation of the FTP sensor: P0497 purge flow NG

The evaporative emission (EVAP) canister vent shut valve is attached to the EVAP canister to control the venting of the EVAP canister to atmosphere.

The EVAP canister vent shut valve is open (open to atmosphere) when the VSV signal is OFF.

If the return signal is "OFF" when the engine control module (ECM)/powertrain control module (PCM) outputs the "ON" signal to the EVAP canister vent shut valve, the ECM/PCM detects a malfunction and a DTC is stored.

The evaporative emission (EVAP) canister vent shut valve is attached to the EVAP canister to control the venting of the EVAP canister to atmosphere.

The EVAP canister vent shut valve is open (open to atmosphere) when the VSV signal is OFF.

If the return signal is "ON" when the engine control module (ECM)/powertrain control module (PCM) outputs the "OFF" signal to the EVAP canister vent shut valve, the ECM/PCM detects a malfunction and a DTC is stored.

A target idle speed that meets the engine operating conditions (coolant temperature, A/C ON or OFF, etc.) is stored in the engine control module (ECM)/powertrain control module (PCM). The ECM/PCM monitors and controls the idle speed so that the actual idle speed is equal to the target idle speed. If the actual idle speed varies beyond a specified value from the target speed over a certain period of time, the ECM/PCM detects a malfunction in the idle speed control system and a DTC is stored.

The quick warm-up system supplies additional air and retards the ignition timing when the engine is cold to activate the catalytic converter as quickly as possible.

When the actual amount of air is less than the target amount, a malfunction is detected and a DTC is stored.

The quick warm-up system supplies additional air and retards the ignition timing when the engine is cold to activate the catalytic converter as quickly as possible.

When the actual engine speed is a specified value or more, and it continues for a specified time, a malfunction is detected and a DTC is stored.

The alternator is driven by the engine, and it generates electricity to supply the necessary power to the electrical system and to charge the battery. The alternator voltage target values of 14.5 V and 12.5 V are achieved by switching the alternator control mode (controlled by the engine control module (ECM)/powertrain control module (PCM)). The alternator output signal is sent to the ECM/PCM, and it varies according to the battery's state of charge, the electrical load, and engine speed.

When the IGP (power source) terminal voltage is a set value or less for a set time, the ECM/PCM detects a malfunction and a DTC is stored.

If there is a short to ground in the harness between the engine control module (ECM)/powertrain control module (PCM) and the PGM-FI main relay 1, the PGM-FI main relay 1 stays ON even though the ignition switch is OFF, and the ECM/PCM remains active. However, the engine is not running because the power for the gauges, the ignition, and the fuel pump is turned OFF by the ignition switch.

When the ECM/PCM operates for a fixed time or more after the ignition switch is turned OFF, a malfunction is detected and a DTC is stored.

The engine control module (ECM)/powertrain control module (PCM) is equipped with an update program to update its control program. The programs in the CPU of the ECM/PCM are classified as an ECM/PCM program (update-capable program) and a program for the update function (non-updateable program). The program update only updates the ECM/PCM program.

When the ECM/PCM power is turned off during an update, the power for the update function is lost, and the update process stops. When the program update is stopped before it is completed, the ECM/PCM stores a DTC that indicates the update is not finished.

If something is wrong in the engine control module (ECM)/powertrain control module (PCM), and the monitor signal from the digital knock system (DKS) CPU is not received for a set period of time, or a signal communication error remains for a set period time, the ECM/PCM detects a malfunction and a DTC is stored.

The engine control module (ECM)/powertrain control module (PCM) is equipped with a keep-alive memory. The data (control learn data etc) for powertrain control and information (Vehicle Identify Number (VIN) etc) related to the vehicle control is stored in the keep alive memory, so that it can be maintained even when power is not supplied to the ECM/PCM such as when the battery is disconnected. When power is restored to the ECM/PCM, the CPU retrieves the stored information from the keep-alive memory, but when the data retrieval process is not finished normally, a malfunction is detected and a DTC is stored.

The CPU writes data to the keep-alive memory from the CPU: Control related data is written when the ignition is turned on, and vehicle information when commanded from the HDS.

If the data writing process is not completed normally, a malfunction is detected and a DTC is stored.

The engine control module (ECM)/powertrain control module (PCM) stores a vehicle identification number (VIN) in the keep-alive memory and outputs the VIN according to the command from the HDS.

The VIN for each vehicle is registered to the ECM/PCM using the HDS. The registered VIN is read by the CPU from the keep-alive memory after the ignition is turned on or after the Clear command is executed.

If the VIN is not registered in the keep-alive memory when the ignition is turned on or when the Clear command is executed, it is detected as a VIN unregistered condition and a DTC is stored.

After the ignition switch is turned off, the engine control module (ECM)/powertrain control module (PCM) does not shut down immediately. After finishing a predetermined process according to the request of each device and system, the power supply is automatically disconnected (self shut-down function). The ECM/PCM power is disconnected by controlling PGM-FI main relay 1 (FI MAIN).

During a normal ECM/PCM shut down, the shut down process is executed by the CPU, PGM-FI main relay 1 (FI MAIN) is turned off, and the voltage to the ECM/PCM is turned off to shut down the ECM/PCM. When the voltage to the ECM/PCM is turned off and the ECM/PCM shuts down without the normal shut down procedure, a malfunction in the PGM-FI main relay 1 (FI MAIN) control circuit is detected and a DTC is stored.

The transmission range switch is attached to the control shaft. Operating the shift lever makes the control shaft rotate via the shift cable. The A/T gear position indicator indicates which position is selected according to the Low/High signal combinations which vary based on shift lever position. The control shaft changes the position of the transmission range switch, activates the manual valve, and switches hydraulic pressure to shift the transmission through forward/neutral/reverse. The transmission range switch signal is used to determine the shift schedule. The voltage is 12 V (High) at the powertrain control module (PCM) input terminal when each transmission range switch position is open, and it is 0 V (Low) when each switch is closed. If the PCM detects multiple switch inputs instead of the correct switch input for the selected range at that time, it detects a malfunction and stores a DTC.

The transmission range switch is attached to the control shaft. Operating the shift lever makes the control shaft rotate via the shift cable. The A/T gear position indicator indicates which position is selected according to the Low/High signal combinations which vary based on the control shaft rotational angle. The control shaft changes the position of the transmission range switch, activates the manual valve, and switches hydraulic pressure to shift the transmission through forward/neutral/reverse. The transmission range switch signal is used to determine the shift schedule. The voltage is 12 V (High) at the powertrain control module (PCM) input terminal when each transmission range switch position is open, and it is 0 V (Low) when each switch is closed. If the FWD switch stays open while the vehicle repeatedly accelerates to a specified vehicle speed and then stops despite being in the D position, the PCM detects a malfunction in the transmission range switch (open) and stores a DTC.

The ATF temperature sensor is a thermistor type sensor whose resistance changes according to the change in ATF temperature. The powertrain control module (PCM) sends a 5 V reference voltage to the grounded sensor through a pull-up resistor. When the ATF temperature is low, the sensor resistance increases and the PCM detects a high signal voltage. As the ATF temperature rises, the sensor resistance decreases and the PCM detects a low signal voltage.

If the ATF temperature sensor signal does not change, the PCM detects a malfunction and a DTC is stored.

When the ATF temperature sensor signal voltage to the PCM is under the specification, indicating that the temperature is above the specification (a short to ground), a malfunction is detected and a DTC is stored.

When the ATF temperature sensor signal voltage to the PCM is above the specification, indicating that the temperature is under the specification (open), a malfunction is detected and a DTC is stored.

The input shaft (mainshaft) speed sensor is attached to the outside of the transmission housing. The input shaft (mainshaft) speed sensor generates a pulsing signal according to the speed of the input shaft (mainshaft) idler gear on the input shaft (mainshaft). Using that signal, the powertrain control module (PCM) determines the speed of the input shaft (mainshaft). If no pulses occur with the input shaft (mainshaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the velocity ratio measured by the output shaft (countershaft) speed sensor and the input shaft (mainshaft) speed sensor, a malfunction is detected and a DTC is stored.

The input shaft (mainshaft) speed sensor is attached to the outside of the transmission housing. The input shaft (mainshaft) speed sensor generates a pulsing signal according to the speed of the input shaft (mainshaft) idler gear on the input shaft (mainshaft). Using that signal, the powertrain control module (PCM) determines the speed of the input shaft (mainshaft). If no pulses occur with the input shaft (mainshaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the correlation between the vehicle speed measured by the output shaft (countershaft) speed sensor and the input shaft (mainshaft) speed sensor, a malfunction is detected and a DTC is stored.

The input shaft (mainshaft) speed sensor is attached to the outside of the transmission housing. The input shaft (mainshaft) speed sensor generates a pulsing signal according to the speed of the input shaft (mainshaft) idler gear on the input shaft (mainshaft). Using that signal, the powertrain control module (PCM) determines the speed of the input shaft (mainshaft). If no pulses occur with the input shaft (mainshaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the fluctuation of the vehicle speed measured by the input shaft (mainshaft) speed sensor, a malfunction is detected and a DTC is stored.

The output shaft (countershaft) speed sensor is attached to the transmission housing to sense output shaft (countershaft) revolutions. The engine control module (ECM) determines the vehicle speed according to the signal from the output shaft (countershaft) speed sensor to the control units. If no signal from the output shaft (countershaft) speed sensor is received for a set time, the ECM detects a malfunction and a DTC is stored.

The output shaft (countershaft) speed sensor is attached to the outside of the transmission housing. The output shaft (countershaft) speed sensor generates a pulsing signal according to the speed of the park gear on the output shaft (countershaft). Using that signal, the powertrain control module (PCM) determines the speed of the output shaft (countershaft). If pulse dropouts occur with the output shaft (countershaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the velocity ratio measured by the input shaft (mainshaft) speed sensor and the output shaft (countershaft) speed sensor, a malfunction is detected and a DTC is stored.

The output shaft (countershaft) speed sensor is attached to the outside of the transmission housing. The output shaft (countershaft) speed sensor generates a pulsing signal according to the speed of the park gear on the output shaft (countershaft). Using that signal, the powertrain control module (PCM) determines the speed of the output shaft (countershaft). If pulse dropouts occur with the output shaft (countershaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the correlation between the vehicle speed measured by the output shaft (countershaft) speed sensor and the input shaft (mainshaft) speed sensor, a malfunction is detected and a DTC is stored.

The output shaft (countershaft) speed sensor is attached to the outside of the transmission housing. The output shaft (countershaft) speed sensor generates a pulsing signal according to the speed of the park gear on the output shaft (countershaft). Using that signal, the powertrain control module (PCM) determines the speed of the output shaft (countershaft). If pulse dropouts occur with the output shaft (countershaft) rotating, the PCM detects a malfunction that may be caused by an open, a temporary open, or a short to ground. Based on the fluctuation of the vehicle speed measured by the output shaft (countershaft) speed sensor, a malfunction is detected and a DTC is stored.

To engage 1st gear, line pressure is supplied to the 1st clutch piston, engaging the 1st clutch, and the secondary shaft and the secondary shaft 1st gear are connected and revolve together. Hydraulic pressure is supplied to the 1st clutch through the ATF strainer --> the ATF pump --> the regulator valve --> the manual valve --> the shift valves --> the feed pipe --> 1st clutch piston. (A shift valve failure in the supply route above is detected by the malfunction detection of each shift solenoid valve.) The powertrain control module (PCM) computes the ratio of the input shaft (mainshaft) speed to the output shaft (countershaft) speed. When the ratio is not the 1st gear ratio, it is detected as a malfunction of the hydraulic circuit or the 1st clutch, and a DTC is stored.

To engage 2nd gear, line pressure is supplied to the 2nd clutch piston, engaging the 2nd clutch, and the secondary shaft and the secondary shaft 2nd gear are connected and revolve together. Hydraulic pressure is supplied to the 2nd clutch through the ATF strainer --> the ATF pump --> the regulator valve --> the manual valve --> the shift valves --> the feed pipe --> 2nd clutch piston. (A shift valve failure in the supply route above is detected by the malfunction detection of each shift solenoid valve.) The powertrain control module (PCM) computes the ratio of the input shaft (mainshaft) speed to the output shaft (countershaft) speed. When the ratio is not the 2nd gear ratio, it is detected as a malfunction of the hydraulic circuit or the 2nd clutch, and a DTC is stored.

To engage 3rd gear, line pressure is supplied to the 3rd clutch piston, the 3rd clutch is engaged, and the secondary shaft and the secondary shaft 3rd gear are connected and revolve together. Hydraulic pressure is supplied to the 3rd clutch through the ATF strainer --> the ATF pump --> the regulator valve --> the manual valve --> the shift valves --> the feed pipe --> 3rd clutch piston. (The shift valve failure in the supplying route above is detected by the malfunction detection of each shift solenoid valve.) The powertrain control module (PCM) computes the ratio of the mainshaft speed to the countershaft speed. When the ratio is not the 3rd gear ratio, it is detected as a malfunction of the hydraulic circuit or the 3rd clutch, and a DTC is stored.

To engage 4th gear, line pressure is supplied to the 4th clutch piston, engaging the 4th clutch, and the input shaft (mainshaft) and the input shaft (mainshaft) 4th gear are connected and revolve together. Hydraulic pressure is supplied to the 4th clutch through the ATF strainer --> the ATF pump --> the regulator valve --> the manual valve --> the shift valves --> the feed pipe --> 4th clutch piston. (A shift valve failure in the supply route above is detected by the malfunction detection of each shift solenoid valve.) The powertrain control module (PCM) computes the ratio of the input shaft (mainshaft) speed to the output shaft (countershaft) speed. When the ratio is not the 4th gear ratio, it is detected as a malfunction of the hydraulic circuit or the 4th clutch, and a DTC is stored.

To engage 5th gear, line pressure is supplied to the 5th clutch piston, engaging the 5th clutch, and the input shaft (mainshaft) and the input shaft (mainshaft) 5th gear are connected and revolve together. Hydraulic pressure is supplied to the 5th clutch through the ATF strainer --> the ATF pump --> the regulator valve --> the manual valve --> the shift valves --> the feed pipe --> 5th clutch piston. (A shift valve failure in the supply route above is detected by the malfunction detection of each shift solenoid valve.) The powertrain control module (PCM) computes the ratio of the input shaft (mainshaft) speed to the output shaft (countershaft) speed. When the ratio is not the 5th gear ratio, it is detected as a malfunction of the hydraulic circuit or the 5th clutch, and a DTC is stored.

The power transfer capacity of the torque converter clutch is controlled by the balance of automatic transmission fluid (ATF) supplied to and discharged from the torque converter. When hydraulic pressure is applied internally, the torque converter clutch turns ON, and when hydraulic pressure is applied from the back pressure side, the lock-up clutch turns OFF. As the hydraulic pressure from the internal pressure side increases, the power transfer capacity of the torque converter clutch increases. The direction of hydraulic pressure supply is switched by shift solenoid valve E and the lock-up shift valve. ATF is supplied from the internal pressure side to shift solenoid valve E when the signal from the powertrain control module (PCM) is ON (12 V), and ATF is supplied from the back pressure side when it is OFF (0 V). The balance of internal pressure and back pressure is controlled by A/T clutch pressure control solenoid valve A and the lock-up control valve. A/T clutch pressure control solenoid valve A maximizes the power transfer capacity of the torque converter clutch when the signal from the PCM is ON (1 A), and it minimizes the power transfer capacity of the torque converter clutch when the signal from the PCM is OFF (0 A). If the ratio of engine speed and mainshaft speed is not about 1:1 while the PCM is issuing the command to turn shift solenoid valve E and A/T clutch pressure control solenoid valve A ON, the PCM detects a faulty lock-up control system and stores a DTC.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft and countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in A/T clutch pressure control solenoid valve A or the hydraulic system is detected and a DTC is stored.

Shift solenoid valve A is installed in the transmission housing. It is controlled by the ON/OFF signal from the powertrain control module (PCM) to apply line pressure to shift valve A. The signal from the PCM is output to apply clutch pressure control pressure to the proper gear change clutch according to the gear change schedule. When the signal to shift solenoid valve A from the PCM is OFF, line pressure is discharged, and shift valve A is inactive. When the signal to shift solenoid valve A from the PCM is ON, line pressure is applied to shift valve A, and it operates against the shift valve A spring. The PCM monitors the mainshaft speed and the countershaft speed at the gear change determined by the shift schedule. When an improper gear ratio is output compared to the predetermined gear change mode, a shift solenoid valve A ON failure is detected and a DTC is stored.

Shift solenoid valve B is installed in the transmission housing. It is controlled by the ON/OFF signal from the powertrain control module (PCM) to apply line pressure to shift valve B. The signal from the PCM is output to apply clutch pressure control pressure to the proper gear change clutch according to the gear change schedule. When the signal to shift solenoid valve B from the PCM is OFF, and line pressure is discharged, shift valve B is inactive. When the signal to shift solenoid valve B from the PCM is ON, and line pressure is applied to shift valve B, it operates against the shift valve B spring. The PCM monitors the mainshaft speed and the countershaft speed at the gear change determined by the shift schedule. When an improper gear ratio is output compared to the predetermined gear change mode, a shift solenoid valve B OFF failure is detected and a DTC is stored.

Shift solenoid valve C is installed in the transmission housing. It is controlled by the ON/OFF signal from the powertrain control module (PCM) to apply line pressure to shift valve C. The signal from the PCM is output to apply clutch pressure control pressure to the proper gear change clutch according to the gear change schedule. When the signal to shift solenoid valve C from the PCM is OFF, line pressure is discharged, and shift valve C is inactive. When the signal to shift solenoid valve C from the PCM is ON, line pressure is applied to shift valve C, and it operates against the shift valve C spring. The PCM monitors the mainshaft speed and the countershaft speed at the gear change determined by the shift schedule. When an improper gear ratio is output compared to the predetermined gear change mode, a shift solenoid valve C OFF failure is detected and a DTC is stored.

Shift solenoid valve E is installed in the transmission housing. It is controlled by the ON/OFF signal from the powertrain control module (PCM) to apply line pressure to shift valve E. The signal from the PCM is output to apply clutch pressure control pressure to the proper gear change clutch according to the gear change schedule. When the signal to shift solenoid valve E from the PCM is OFF, line pressure is discharged, and shift valve E is inactive. When the signal to shift solenoid valve E from the PCM is ON, line pressure is applied to shift valve E, and it operates against the shift valve E spring. The PCM monitors the mainshaft speed and the countershaft speed at the gear change determined by the shift schedule. When an improper gear ratio is output compared to the predetermined gear change mode, a shift solenoid valve E OFF failure is detected and a DTC is stored.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft and countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in A/T clutch pressure control solenoid valve B or the hydraulic system is detected and a DTC is stored.

This fault code is a general (specified by SAE) DTC that is stored at a time the following DTC codes (P1730, P1731, P01732, P1733 and P1734) are detected.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft and countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in A/T clutch pressure control solenoid valve C or the hydraulic system is detected and a DTC is stored.

If the 2nd clutch transmission fluid pressure switch is ON while driving the vehicle with the speed ratio of the countershaft to mainshaft other than 2nd (the ratio is Neutral or 4th), the PCM detects a 2nd clutch transmission fluid pressure switch failure and a DTC is stored.

The 2nd clutch transmission fluid pressure switch is installed in the hydraulic pressure circuit to the 2nd clutch. When hydraulic pressure is supplied to the 2nd clutch, the switch is turned ON. When hydraulic pressure is not supplied to the 2nd clutch, the switch is turned OFF. The signal of the 2nd clutch transmission fluid pressure switch is input to the powertrain control module (PCM). The PCM detects the hydraulic pressure supply conditions at the gear change to 2nd gear (1st --> 2nd, 3rd --> 2nd) to reduce the shock that occurs at the gear change. If the 2nd clutch transmission fluid pressure switch is OFF while driving with the rotation speed ratio of the input/output pulses in 2nd gear, the PCM detects a malfunction in the 2nd clutch transmission fluid pressure switch and stores a DTC.

If the 3rd clutch transmission fluid pressure switch is ON while driving the vehicle with the speed ratio of the countershaft to mainshaft in other than 3rd gear (the ratio is Neutral or 4th), the PCM detects a 3rd clutch transmission fluid pressure switch failure and a DTC is stored.

The 3rd clutch transmission fluid pressure switch is installed in the hydraulic pressure circuit to the 3rd clutch. When hydraulic pressure is supplied to the 3rd clutch, the switch is turned ON. When hydraulic pressure is not supplied to the 3rd clutch, the switch is turned OFF. The signal of the 3rd clutch transmission fluid pressure switch is input to the powertrain control module (PCM). The PCM detects the hydraulic pressure supply conditions at the gear change to 3rd gear (2nd --> 3rd, 4th --> 3rd) to reduce the shock that occurs at the gear change. If the 3rd clutch transmission fluid pressure switch is OFF while driving with the rotation speed ratio of the input/output pulses in 3rd gear, the PCM detects a malfunction in the 3rd clutch transmission fluid pressure switch and stores a DTC.

A/T clutch pressure control solenoid valve A is used for clutch pressure control and lock-up control. A spool in A/T clutch pressure control solenoid valve A pushes a valve according to the duty cycle that is controlled by the powertrain control module (PCM) to pressurize fluid so the hydraulic pressure is proportional to the current. The PCM measures the current flowing through A/T clutch pressure control solenoid valve A and uses feedback control to compensate the difference between the actual current and the commanded one. If the measured current for the PCM output duty cycle is not within a specified range (open or short), a malfunction is detected and a DTC is stored.

A/T clutch pressure control solenoid valve B is used for clutch pressure control. A spool in A/T clutch pressure control solenoid valve B pushes a valve according to the duty cycle that is controlled by the powertrain control module (PCM) to pressurize fluid so the hydraulic pressure is proportional to the current. The PCM measures the current flowing through A/T clutch pressure control solenoid valve B and uses feedback control to compensate the difference between the actual current and the commanded one. If the measured current for the PCM output duty cycle is not within a specified range (open or short), a malfunction is detected and a DTC is stored.

A/T clutch pressure control solenoid valve C is used for clutch pressure control. A spool in A/T clutch pressure control solenoid valve C pushes a valve according to the duty cycle that is controlled by the powertrain control module (PCM) to pressurize fluid so the hydraulic pressure is proportional to the current. The PCM measures the current flowing through A/T clutch pressure control solenoid valve C and uses feedback control to compensate the difference between the actual current and the commanded one. If the measured current for the PCM output duty cycle is not within a specified range (open or short), a malfunction is detected and a DTC is stored.

When shift solenoid valves A, B, C, D, and E are turned ON, the hydraulic pressure circuit opens. The hydraulic pressure circuit supplies/discharges hydraulic pressure to/from each clutch according to the combination of the ON/OFF status of those valves and the shift valves. The powertrain control module (PCM) commands the driver circuit to turn on the shift solenoid valve. The circuit diagnoses malfunctions such as a circuit short or open, and sends back a return signal during the PCM's command. When the return signal does not match the PCM command, a malfunction is detected by the PCM. The malfunction is detected when the return signal does not match the PCM command to turn ON the shift solenoid valve, and a DTC is stored.

The variable valve timing control (VTC) system controls the phase of the intake camshaft. It uses oil pressure to operate the VTC actuator so the valve timing is optimized depending on driving conditions. The engine control module (ECM)/powertrain control module (PCM) monitors the phase control command and the actual timing of the camshaft by using camshaft position (CMP) sensor A. If an over-advanced camshaft phase (compared to the directed value) continues or when the camshaft phase is otherwise abnormal, a malfunction is detected and a DTC is stored.

The barometric pressure (BARO) sensor is built into the engine control module (ECM)/powertrain control module (PCM), and it monitors atmospheric pressure. The ECM/PCM estimates appropriate intake airflow from the manifold absolute pressure (MAP) sensor output voltage and BARO sensor output voltage. When BARO sensor output voltage is within the specified range, a malfunction is detected and a DTC is stored.

Two engine coolant temperature sensors and one intake air temperature sensor are used by the engine control module (ECM)/powertrain control module (PCM).

When the engine is stopped and enough time has passed, the temperature of the engine will equal the ambient temperature.

When an inappropriate temperature is detected after comparing the temperature readings of each sensor, a malfunction in the corresponding sensor is detected and a DTC is stored.

The engine control module (ECM)/powertrain control module (PCM) compares a predetermined MAP value at a given throttle position and manifold absolute pressure to the output voltage value of the MAP sensor.

If the MAP sensor outputs lower voltage than expected, the ECM/PCM detects a malfunction and stores a DTC.

If the MAP sensor outputs high voltage during fuel cut-off operation for deceleration with the throttle valve fully closed, which should make the manifold absolute pressure lower, the ECM/PCM detects a malfunction and stores a DTC.

The air/fuel ratio (A/F) sensor (sensor 1) is installed in the exhaust system and detects oxygen content in the exhaust gas.

The A/F sensor outputs voltage to the engine control module (ECM)/powertrain control module (PCM). A heater for the sensor element is embedded in the A/F sensor (sensor 1). When activated, it heats the sensor to stabilize and speed up the detection of oxygen content by controlling current flow through the heater. The current diminishes as the voltage applied to the element reaches a certain range because the amount of oxygen that passes through the diffusion layer is limited. The current is proportional to the oxygen content in the exhaust gas, so the air/fuel ratio is detected by the measurement of the current. The ECM/PCM compares the set target air/fuel ratio to the detected air/fuel ratio and adjusts the fuel injection duration.

If the A/F sensor (sensor 1) voltage is low, the air/fuel ratio is lean, and the ECM/PCM uses A/F feedback control to issue a Rich command. If the A/F sensor (sensor 1) voltage is high, the air/fuel ratio is rich, and the ECM/PCM uses A/F feedback control to issue a Lean command.

If the element is not activated for a set time when power is drawn by the A/F sensor (sensor 1) heater, a malfunction is detected and a DTC is stored.

If a malfunction causes the air/fuel sensor value sent to the engine control module (ECM)/powertrain control module (PCM) to deviate from the normal control area, the air/fuel (A/F) sensor may still become active after the engine starts, but the air/fuel feedback does not start normally and the emissions deteriorate. When the A/F sensor output is out of the normal area, and this condition continues after the A/F sensor is active, the ECM/PCM detects a malfunction and a DTC is stored.

The electrical load detector (ELD) is built into the under-hood fuse/relay box. It monitors the current fed to the ignition switch and sends a signal to the engine control module (ECM)/powertrain control module (PCM). If the ELD output voltage is extremely low, a malfunction is detected and a DTC is stored.

The electrical load detector (ELD) is built into the under-hood fuse/relay box. It monitors the current fed to the ignition switch and sends a signal to the engine control module (ECM)/powertrain control module (PCM). If the ELD output voltage is extremely high, a malfunction is detected and a DTC is stored.

The fuel tank pressure is about 0 kPa (0 in.Hg, 0 mmHg) when starting a cold engine. When the fuel tank pressure (FTP) sensor output value is out of a specified range and the engine control module (ECM)/powertrain control module (PCM) judges that there's no other cause [no evaporative emission (EVAP) canister vent shut valve failure, etc.] of the FTP sensor zero point shift, the ECM/PCM detects an FTP sensor malfunction.

However, if the FTP sensor output when starting the engine is a prescribed negative value or less (excessive negative pressure is detected), the malfunction judgment should be done as follows because it is difficult to distinguish the FTP sensor zero point shift (P1454) from the EVAP canister vent shut valve failure (P2422).

If either Temporary DTC P1454 or P2422 is not stored, the ECM/PCM stores both DTCs.
If both P1454 and P2422 Temporary DTCs are stored and an excessive negative pressure is detected, both P1454 and P2422 DTCs are stored.
If either Temporary DTC P1454 or P2422 is stored and an excessive negative pressure is detected, the ECM/PCM stores the DTC of the temporary DTC that was stored.

< STEP 1 >

OK determination: Pulse exists (P145C OK)

P0497 Purge flow OK
P0496 EVAP canister purge valve Open fix OK

NG determination: No pulse (P145C NG)

Either purge flow P0497 abnormality or P0496 EVAP canister purge valve OPEN failure.
In this case, classify the failure part according to < STEP 2 >.

< STEP 2 >

In case there is no pulse, it is determined either no purge flow or EVAP canister purge valve OPEN fix as follows

When the FTP sensor fluctuates from negative pressure condition to atmospheric pressure side after the ignition is turned off: P0496 EVAP canister purge valve OPEN fix

When there is no fluctuation of the FTP sensor: P0497 purge flow NG

When the IGP terminal voltage of the ECM/PCM is a set value or more for a set time, a malfunction is detected and a DTC is stored.

The electronic throttle control system controls the throttle valve opening. The system is composed of the throttle actuator, the throttle valve, throttle position (TP) sensors A and B, the throttle actuator control module, the throttle actuator control module relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM)/powertrain control module (PCM). The throttle valve default position spring is attached to the throttle valve gear. It opens the throttle valve to improve starting performance in cold conditions, or to retain minimum running performance in case of an electronic throttle control system failure.

If the throttle valve does not return to the default position when the throttle actuator control module moves the throttle actuator to the default position from the fully closed position, a malfunction is detected and the malfunction data is transmitted to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a malfunction in the throttle valve default position spring, and a DTC is stored.

If the throttle valve does not return to the default position when the throttle actuator control module moves the throttle actuator to the default position from the middle position, a malfunction is detected and the malfunction data is transmitted to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a malfunction in the throttle valve return spring and a DTC is stored.

When the engine speed is a specified value and the IGP terminal voltage is below a set value when the alternator is in the 14.5 V mode, and the alternator power generation amount is within the set range, and this condition continues more than a set time, the ECM/PCM detects a malfunction and a DTC is stored.

The alternator is driven by the engine, and it generates electricity to supply the necessary power to the electrical load and to charge the battery. The alternator voltage target values of 14.5 V and 12.5 V are achieved by switching the alternator control mode (controlled by the engine control module (ECM)/powertrain control module (PCM)). The alternator output signal is sent to the ECM/PCM, and it varies according to the battery's state of charge, the electrical load, and the engine speed.

When the engine speed is a specified value and the IGP terminal voltage is below a set value when the alternator is in the 14.5 V mode, and the alternator power generation amount is a set range or less, and this condition continues more than a set time, the ECM/PCM detects a malfunction and a DTC is stored.

The transmission range switch is attached to the control shaft. Operating the shift lever makes the control shaft rotate via the shift cable. The A/T gear position indicator indicates which position is selected according to the Low/High signal combinations which vary based on shift lever position. The control shaft changes the position of the transmission range switch, activates the manual valve, and switches hydraulic pressure to shift the transmission through forward/neutral/reverse. The transmission range switch signal is used to determine the shift schedule. The voltage is 12 V (High) at the powertrain control module (PCM) input terminal when each transmission range switch position is open, and it is 0 V (Low) when each switch is closed. If the RVS switch is OPEN with the shift lever in the R position while shifting between the P, R, and N positions, the PCM detects a RVS switch OPEN failure and a DTC is stored.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft to countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in the shift solenoid valve or the hydraulic system is detected and a DTC is stored.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft to countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in the A/T clutch pressure control solenoid valve, the shift solenoid valve, or the hydraulic system is detected and a DTC is stored.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft to countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in the shift solenoid valve or the hydraulic system is detected and a DTC is stored.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft to countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in the A/T clutch pressure control solenoid valve, the shift solenoid valve, or the hydraulic system is detected and a DTC is stored.

Hydraulic pressure to each clutch is controlled by the shift valve. The shift valve activates according to the ON/OFF status of shift solenoid valves A, B, C, D, and E. Hydraulic pressure supply in D position is shown above. The line pressure or the clutch pressure control pressure (CPC A, CPC B, or CPC C) is supplied to each clutch by the shift valve activated. The powertrain control module (PCM) computes the actual ratio of mainshaft to countershaft revolutions. If a difference between the actual ratio and the commanded gear occurs when shifting to each gear position, a malfunction in the shift solenoid valve or the hydraulic system is detected and a DTC is stored.

The electronic throttle control system (ETCS) controls the throttle valve opening. The system is composed of the throttle actuator, the throttle valve, throttle position (TP) sensors A and B, the throttle actuator control module, the throttle actuator control module relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM)/powertrain control module (PCM).

The APP sensor is operated via the throttle cable to determine the accelerator opening value when the driver presses the accelerator pedal. The accelerator pedal opening value is converted to a signal in the APP sensor and transmitted to the ECM/PCM to compute the target position. The target position signal is then transmitted to the throttle actuator control module.

The throttle actuator control module determines the throttle valve target position according to the signal received and operates the throttle actuator to move the throttle valve to the target position. The actual throttle valve position is determined by TP sensor A installed in the throttle body.

The throttle actuator control module compares the throttle valve target opening angle and the actual throttle valve opening angle from TP sensor A, and when the difference exceeds the specification, the throttle actuator control module transmits the malfunction data to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects the malfunction of the throttle actuator system and a DTC is stored.

The electronic throttle control system controls the throttle valve opening. The system is composed of the throttle actuator, the throttle valve, throttle position (TP) sensors A and B, the throttle actuator control module, the throttle actuator control module relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM)/powertrain control module (PCM). The APP sensor is operated via the throttle cable to determine the accelerator opening value when the driver presses the accelerator pedal. The accelerator pedal opening value is converted to a signal in the APP sensor and transmitted to the ECM/PCM to compute the target position. The target position signal is then transmitted to the throttle actuator control module.

The CPU in the throttle actuator control module performs self-diagnosis for the ROM, the RAM, and the A/D converter. If internal data is found to be abnormal, a malfunction is detected and the malfunction data is transmitted to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a malfunction in the throttle actuator control module and stores a DTC. When the ECM/PCM monitors the serial signal between the ECM/PCM and the throttle actuator control module and finds disagreement on these signals, the ECM/PCM detects a malfunction and a DTC is stored.

When the output voltage to the throttle actuator exceeds the specification for a set time, the throttle actuator control module detects a malfunction and transmits the malfunction data to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a malfunction of the throttle actuator system and stores a DTC.

Accelerator pedal position (APP) sensor A is a part of the electronic throttle control system, and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM)/powertrain control module (PCM) controls the throttle actuator so that the throttle position agrees with the accelerator pedal position. If the signal voltage from APP sensor A is a set value or less, the ECM/PCM detects a malfunction and stores a DTC.

Accelerator pedal position (APP) sensor A is a part of the electronic throttle control system, and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM)/powertrain control module (PCM) controls the throttle actuator so that the throttle position agrees with the accelerator pedal position. If the signal voltage from APP sensor A is a set value or more, the ECM/PCM detects a malfunction and stores a DTC.

Accelerator pedal position (APP) sensor B is a part of the electronic throttle control system, and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM)/powertrain control module (PCM) controls the throttle actuator so that the throttle position agrees with the accelerator pedal position. If the signal voltage from APP sensor B is a set value or less, the ECM/PCM detects a malfunction and stores a DTC.

Accelerator pedal position (APP) sensor B is a part of the electronic throttle control system, and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM)/powertrain control module (PCM) controls the throttle actuator so that the throttle position agrees with the accelerator pedal position. If the signal voltage from APP sensor B is a set value or more, the ECM/PCM detects a malfunction and stores a DTC.

The throttle actuator control module compares the voltages and the throttle valve positions of TP sensor A and TP sensor B. If the difference of the voltages or the throttle valve positions is a certain value or less for a set time, the throttle actuator control module detects a malfunction and the malfunction data is transmitted to the ECM/PCM. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a malfunction in the relationship between TP sensor A and TP sensor B, and stores a DTC.

Accelerator pedal position (APP) sensor A and accelerator pedal position (APP) sensor B are potentiometers, and they are installed in the engine compartment.

The APP sensors A and B are operated via the throttle cable to determine the accelerator opening value when the driver presses the accelerator pedal. The accelerator pedal opening value is converted to a signal in APP sensors A and B and transmitted to the engine control module (ECM)/powertrain control module (PCM) to compute the target position. The target position signal is then transmitted to the throttle actuator control module.

APP sensor A is for the primary control, and APP sensor B is a back-up of APP sensor A in case it malfunctions. Both sensors compare their output voltage to each other for malfunction detection.

When the voltage difference of APP sensor B is out of a fixed range for a set period of time, the ECM/PCM detects a malfunction, and a DTC is stored.

The electronic throttle control system controls the throttle valve opening. The system is composed of the throttle actuator, the throttle valve, throttle position (TP) sensors A and B, the throttle actuator control module, the throttle actuator control module relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM)/powertrain control module (PCM). The APP sensor is operated via the throttle cable to determine the accelerator opening value when the driver presses the accelerator pedal. The accelerator pedal opening value is converted to a signal in the APP sensor and transmitted to the ECM/PCM to compute the target position. The target position signal is then transmitted to the throttle actuator control module.

The throttle actuator control module transmits a signal to the throttle actuator and moves the throttle valve to the fully closed position to register the throttle valve fully closed position after the ignition switch is turned ON.

The throttle actuator control module detects the malfunction of the throttle actuator control system, and it transmits a malfunction signal to the ECM/PCM when the registration of the throttle valve fully closed position is not completed within a predetermined time or the registered value is out of predetermined range after the ignition switch is turned ON. When the ECM/PCM receives the malfunction data from the throttle actuator control module, the ECM/PCM detects a malfunction in the throttle actuator control system and stores a DTC.

Two engine coolant temperature sensors and one intake air temperature sensor are used by the engine control module (ECM)/powertrain control module (PCM).

The engine coolant temperature (ECT) sensor 2 is a thermistor attached to the radiator. The ECM/PCM applies voltage (about 5 V) to the ECT2 signal circuit through a pull up resistor. As the engine coolant temperature cools, ECT sensor 2 resistance increases, and the ECM/PCM detects a high signal voltage. As the engine coolant warms, the sensor resistance decreases, and the ECM/PCM detects a low ECT2 signal voltage.

If the ECT sensor 2 output voltage is less than a set value when the engine coolant temperature is high, the ECM/PCM detects a malfunction and a DTC is stored.

If the ECT sensor 2 output voltage is more than a set value when the engine coolant temperature is low, the ECM/PCM detects a malfunction and a DTC is stored.

When the air/fuel ratio (A/F) sensor (sensor 1) is properly connected to the engine wire harness, but not installed in the exhaust pipe, the A/F feedback is not done properly even if the A/F sensor is active after starting the engine. Thus, the exhaust emissions increase.

When the A/F sensor output stays out of the normal range after the A/F sensor becomes active, the engine control module (ECM)/powertrain control module (PCM) detects that the A/F sensor is not properly installed and a DTC is stored.

The barometric pressure (BARO) sensor is built into the engine control module (ECM)/powertrain control module (PCM) and monitors atmospheric pressure. When the throttle valve is wide open, the manifold absolute pressure (MAP) sensor output is nearly equal to the BARO sensor output. Making use of this characteristic, a malfunction can be detected in the BARO sensor output.

If the throttle position is beyond a value stored in the ECM/PCM that is used to detect "wide-open throttle," and if the difference between the MAP sensor output and the BARO sensor output is equal to or greater than a set value, a malfunction in the BARO sensor output is detected and a DTC is stored.

The barometric pressure (BARO) sensor is built into the engine control module (ECM)/powertrain control module (PCM), and it monitors atmospheric pressure. The ECM/PCM estimates appropriate intake airflow from the manifold absolute pressure (MAP) sensor output voltage and BARO sensor output voltage. If the BARO sensor output voltage is a specified value or less, the ECM/PCM detects a malfunction and a DTC is stored.

The barometric pressure (BARO) sensor is built into the engine control module (ECM)/powertrain control module (PCM), and it monitors atmospheric pressure. The ECM/PCM estimates appropriate intake airflow from the manifold absolute pressure (MAP) sensor output voltage and BARO sensor output voltage. If the BARO sensor output voltage is a specified value or more, the ECM/PCM detects a malfunction and a DTC is stored.

The air/fuel ratio (A/F) sensor (sensor 1) is installed in the exhaust system and detects oxygen content in the exhaust gas. The A/F sensor transmits a signal to the engine control module (ECM)/powertrain control module (PCM). A heater for the sensor element is embedded in the A/F sensor (sensor 1). It heats the sensor to stabilize and speed up the detection of oxygen content. The increase in current through the heater levels off as the voltage applied to the electrode reaches a certain range because the amount of oxygen that goes through the diffusion layer is limited. The current is proportional to oxygen content in the exhaust gas, so the air/fuel ratio is detected by the measurement of the current. The ECM/PCM compares a set target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection duration.

If the element is not activated or the ECM/PCM terminal voltage is a set value or less for a set time when power is applied to the A/F sensor (sensor 1) heater, a malfunction is detected and a DTC is stored.

The secondary HO2S detects the oxygen concentration in the exhaust gas downstream of the three-way catalyst (TWC).

The sensor output voltage characteristics are similar to the air/fuel ratio (A/F) sensor. The oxygen concentration is detected after the TWC during fuel feedback control using the A/F sensor, and it optimizes the fuel feedback control to maximize the effect of the TWC. If, after current is applied to the secondary HO2S heater, the secondary HO2S does not fluctuate and the output is stuck within the specified area, a malfunction is detected and a DTC is stored.

The secondary HO2S detects the oxygen concentration in the exhaust gas downstream of the three-way catalyst (TWC).

The fuel tank pressure (FTP) sensor output indicates about atmospheric pressure 0 kPa (0 in.Hg, 0 mmHg) before purge starts since the evaporative emission (EVAP) canister vent shut valve is normally open (open to the atmosphere). The sensor indicates a negative pressure value (vacuum) during purging.

When the FTP sensor indicates vacuum after starting the engine, there is the possibility of an FTP sensor zero point shift failure or an EVAP canister vent shut valve stuck closed failure. So the engine control module (ECM)/powertrain control module (PCM) monitors the FTP sensor output after purge starts. The ECM/PCM detects a malfunction of the EVAP canister vent shut valve if the output indicates excessive vacuum.

However, if the fuel tank internal pressure is below the specified value (excessive vacuum is detected) when starting the engine, the malfunction detection should be done as follows because it is difficult to distinguish the FTP sensor range problem (P1454) from the EVAP canister vent shut valve stuck closed (P2422).

If neither Temporary DTC (P1454 nor P2422) is stored, both DTCs are stored.
If both Temporary DTCs (P1454 and P2422) are stored and excessive vacuum is detected, both DTCs are stored.
If either Temporary DTC (P1454 or P2422) is stored and excessive vacuum is detected, the ECM/PCM stores the DTC of the Temporary DTC that was stored.

The electronic throttle control system (ETCS) controls the throttle valve opening. The system is composed of the throttle actuator, the throttle valve, throttle position (TP) sensors A and B, the throttle actuator control module, and the throttle actuator control module relay in the throttle body.

The accelerator pedal position (APP) sensor is operated via the throttle cable to determine the accelerator opening value when the driver presses the accelerator pedal. The accelerator pedal opening value is converted to a signal in the APP sensor, transmitted to the engine control module (ECM)/powertrain control module (PCM), and then transmitted to the throttle actuator control module.

The ECM/PCM detects the malfunction of the throttle actuator control module relay ON, and a DTC is stored if the serial signal from the throttle actuator control module is input for more than a set time after the throttle actuator control module relay is turned OFF and throttle actuator control module operation is stopped.

The engine control module (ECM)/powertrain control module (PCM) has a built-in ignition off timer that measures the duration of time from ignition off to the next ignition on. The measured duration is used for evaporative emission (EVAP) leak detection and temperature assumption of the catalytic converter.

The CPU in the ECM/PCM accesses the ignition off timer when reading the measured duration. When the access process fails, a malfunction is detected and a DTC is stored. When an abnormality is found in the read data, a malfunction is detected and a DTC is stored.

The VTEC system activates the rocker arm oil control solenoid by command from the engine control module (ECM)/powertrain control module (PCM), and it charges/discharges the hydraulic circuit of the VTEC mechanism that switches valve timing between Low and High. The ECM/PCM monitors oil pressure in the hydraulic circuit of the VTEC mechanism using the rocker arm oil pressure switch downstream of the rocker arm oil control solenoid. If there is a difference between the oil pressure condition in the hydraulic circuit that is determined by the ECM/PCM command and the oil pressure condition that is determined by the status of the rocker arm oil pressure switch, the system is considered faulty, and a DTC is stored.

The air/fuel ratio (A/F) sensor has a linear signal output in relation to the oxygen concentration. The engine control module (ECM)/powertrain control module (PCM) computes the air/fuel ratio from A/F sensor output voltage and uses the fuel feedback control to improve exhaust emissions. The ECM/PCM monitors A/F sensor output voltage during deceleration with the throttle fully closed, and if the output voltage deviates greatly from normal oxygen concentration levels, it detects a malfunction and stores a DTC.

* Output to the scan tool exhibits a relationship between the A/F sensor output and oxygen concentration, which is opposite to the characteristic shown in the graph. That is, a deviation toward the rich side increases the output voltage and one toward the lean side decreases the output voltage as the stoichiometric ratio is 0.

The controller area network (CAN) transmits/receives pulsing signals to/from the control modules simultaneously by using two signal lines (CANH and CANL).

When the engine control module (ECM)/powertrain control module (PCM) does not receive the signals via the CAN lines for more than a set time, the ECM/PCM detects a malfunction and a DTC is stored.

The engine control module (ECM)/powertrain control module (PCM) uses the serial signal line for two-way communication with the throttle actuator control module.

The ECM/PCM transmits the accelerator pedal position signal to the throttle actuator module, and the throttle actuator control module transmits the actual throttle valve position signal, or a malfunction signal, etc., to the ECM/PCM via this line.

When no serial signals from the throttle actuator control module are received or the serial signals are abnormal for more than a set time, the ECM/PCM detects a malfunction and a DTC is stored.

The controller area network (CAN) transmits/receives pulsing signals to/from the control modules simultaneously by using two signal lines (CANH and CANL).

When the engine control module (ECM)/powertrain control module (PCM) does not receive the signals via the CAN lines for more than a set time, the ECM/PCM detects a malfunction and a DTC is stored.

The controller area network (CAN) transmits/receives pulsing signals to/from the control modules simultaneously by using two signal lines (CANH and CANL).

When the engine control module (ECM)/powertrain control module (PCM) does not receive the signals from the gauge control module via the CAN lines for more than a set time, the ECM/PCM detects a malfunction and a DTC is stored.

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