Advanced Diagnostics: Overview Honda S2000 I

Manifold Absolute Pressure (MAP) Sensor Circuit - Wiring Diagram. Scheme 158

Manifold Absolute Pressure (MAP) Sensor Output Voltage - Graph. Scheme 159

General Description

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 less, the engine control module (ECM) detects a malfunction and a DTC is stored.

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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) detects a malfunction and a DTC is stored.

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

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.

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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) detects a malfunction and a DTC is stored.

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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 high, the engine control module (ECM) detects a malfunction and a DTC is stored.

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The engine control module (ECM) 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 detects a high signal voltage. As the engine coolant warms, ECT sensor 1 resistance decreases, and the ECM 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.

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The engine coolant temperature (ECT) sensor 1 is used for the air fuel ratio feedback control, the ignition timing control, the 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) detects a high signal voltage. As the engine coolant warms, the ECT sensor 1 resistance decreases, and the ECM 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 detects a malfunction and a DTC is stored.

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The 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) detects a high signal voltage. As the engine coolant warms, the ECT sensor 1 resistance decreases, and the ECM 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 detects a malfunction and a DTC is stored.

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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) as an actual throttle valve position signal.

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

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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) as an actual throttle valve position signal.

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

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The engine control module (ECM) 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 detects a high signal voltage. As the engine coolant warms, the ECT sensor 1 resistance decreases, and the ECM 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 detects a malfunction and a DTC is stored.

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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) measures the rise in the coolant temperature after the engine starts using engine block and the engine coolant temperature at 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.

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The air/fuel ratio (A/F) sensor has a linear signal output in relation to the oxygen concentration. The engine control module (ECM) computes the air/fuel ratio from A/F sensor output voltage and uses fuel feedback control to improve exhaust emissions. The ECM 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.

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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) monitors the A/F sensor condition by monitoring the A/F sensor internal resistance.

1. 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.
2. 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.

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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). It heats the sensor to stabilize and speed 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.

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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 primary heated oxygen sensor (HO2S) (sensor 1) output voltage. The secondary HO2S controls the air/fuel ratio from the primary HO2S 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.

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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 primary heated oxygen sensor (HO2S) (sensor 1) output voltage. The secondary HO2S controls the air/fuel ratio from the primary HO2S output voltage to optimize TWC efficiency.

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.

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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.

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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). 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 more or less than a specified amperage, the ECM detects a malfunction and a DTC is stored.

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The engine control module (ECM) detects the oxygen content in the exhaust gas from the air/fuel ratio (A/F) sensor (sensor 1) signal voltage, and it performs 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 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 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.

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The engine control module (ECM) detects the oxygen content in the exhaust gas from the air/fuel ratio (A/F) sensor (sensor 1) signal voltage, and it performs 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 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 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.

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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) as an actual throttle valve position signal.

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

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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) as an actual throttle valve position signal.

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

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The crankshaft vibrates slightly when each cylinder fires. If a misfire occurs, the crankshaft rotation speed changes rapidly. The engine control module (ECM) 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 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.

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The crankshaft vibrates slightly when each cylinder fires. If a misfire occurs, the crankshaft rotation speed changes rapidly. The engine control module (ECM) monitors engine misfiring based on the output pulses from the crankshaft position (CKP) sensor, counts the number of misfires, and determines which cylinder is misfiring. If a misfire is detected, 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.

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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) 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 detects a malfunction and stores a DTC.

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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). 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.

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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). The CKP sensor detects injection/ignition timing for each cylinder and engine speed.

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

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Camshaft position (CMP) sensor 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). The CMP sensor detects the top dead center of each cylinder for fuel injection timing. If no CMP sensor pulsing signals are detected, a malfunction is detected and a DTC is stored.

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The camshaft position (CMP) sensor 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). The CMP sensor detects the top dead center of each cylinder for fuel injection timing.

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

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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.

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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) does not turn on the EVAP canister purge valve when the engine coolant temperature is 149°F (65°C) or less. The ECM 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 detects a malfunction, and a DTC is stored.

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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) 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 detects a malfunction and stores a DTC.

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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) 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 detects a malfunction and stores a DTC.

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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) 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 within a set time after starting the engine in a cold condition, the ECM detects a malfunction and stores a DTC.

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The evaporative emission (EVAP) leak detection system uses a vacuum-retention (decompression) method and an engine off natural vacuum (EONV) method. This method detects leakage by monitoring the vacuum-retention ability of the EVAP system (from EVAP canister purge valve to fuel tank). 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 0: Judgement of detection of 0.09 inch leak as normal operation < decompressing monitor >

Step 1: Judgement of detection of 0.02 inch leak as normal operation < phase 1 >

Step 2: Detection of 0.02 inch leak < phase 2 >

Step 0

Once required conditions for the monitor are met, the engine control module (ECM) applies vacuum to the EVAP system line from the purge control solenoid (PCS) valve through the fuel tank, and monitors the variation of the FTP sensor output to detect a "0.09 inch leak".

1. If a "0.09 inch leak" is detected, it is identified as a malfunction; the diagnosis is complete.
2. If "no 0.09 inch leak" is detected, the ECM goes to step 1, judgement of detection of a 0.02 inch leak as normal operation < phase 1 >.
3. If sufficient vacuum cannot be drawn on the EVAP system line, it is identified as either "EVAP system low purge flow (P0497)" or "EVAP system leak detected fuel fill cap loose/off (P0457)" (refer to the ).

Step 1

After the engine has stopped, the ECM 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.

1. If "no 0.02 inch leak" is detected, it is identified as normal; the diagnosis is complete.
2. If "no 0.02 inch leak" is not detected, the ECM goes to step 2, detection of a 0.02 inch leak < phase 2 >.

Step 2

The ECM 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.

1. If a "0.02 inch leak" is detected, it is identified as a malfunction; the diagnosis is complete.
2. If "no leakage" is detected, it is identified as normal; the diagnosis is complete.

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The evaporative emission (EVAP) leak detection system uses a vacuum-retention (decompression) method and an engine off natural vacuum (EONV) method. This method detects leakage by monitoring the vacuum-retention ability of the EVAP system (from EVAP canister purge valve to fuel tank). 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 0: Judgement of detection of 0.09 inch leak as normal operation < decompressing monitor >

Step 1: Judgement of detection of 0.02 inch leak as normal operation < phase 1 >

Step 2: Detection of 0.02 inch leak < phase 2 >

Step 0

Once required conditions for the monitor are met, the engine control module (ECM) applies vacuum to the EVAP system line from the purge control solenoid (PCS) valve through the fuel tank, and monitors the variation of the FTP sensor output to detect a "0.09 inch leak".

1. If a "0.09 inch leak" is detected, it is identified as a malfunction; the diagnosis is complete.
2. If "no 0.09 inch leak" is detected, the ECM goes to step 1, judgement of detection of a 0.02 inch leak as normal operation < phase 1 >.
3. If sufficient vacuum cannot be drawn on the EVAP system line, it is identified as either "EVAP system low purge flow (P0497)" or "EVAP system leak detected fuel fill cap loose/off (P0457)" (refer to ).

Step 1

After the engine has stopped, the ECM 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.

1. If "no 0.02 inch leak" is detected, it is identified as normal; the diagnosis is complete.
2. If "no 0.02 inch leak" is not detected, the ECM goes to step 2, detection of a 0.02 inch leak < phase 2 >.

Step 2

The ECM 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.

1. If a "0.02 inch leak" is detected, it is identified as a malfunction; the diagnosis is complete.
2. If "no leakage" is detected, it is identified as normal; the diagnosis is complete.

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There are two conditions when the evaporative emission (EVAP) system will not hold vacuum sufficiently, and the pressure in the fuel tank doesn't become negative.

1. EVAP system low purge flow.
2. EVAP system leakage or the fuel fill cap is loose/off.

Here is a description of condition 2

The engine control module (ECM) monitors the fuel tank pressure (FTP) sensor output. If the FTP sensor output does not indicate the specified vacuum when applying vacuum when the fuel vapor density is high, the ECM detects a large leak (fuel fill cap loose/off) and a DTC is stored. [The malfunction detection is performed during EVAP system leak detection (P0455, P0456).]

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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) 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.

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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 assembly, is sent to the engine control module (ECM) via SEFMJ. If the ECM 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.

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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 assembly, is sent to the engine control module (ECM) via SEFMJ. If the ECM 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.

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The engine control module (ECM) adjusts the amount of fuel vapor sent to the engine by controlling the evaporative emission (EVAP) canister purge valve. If the EVAP canister purge valve is stuck open, engine vacuum flows into the purge line before purge control starts when starting the engine. The ECM monitors the fuel tank pressure (FTP) sensor output when purge control starts. If the FTP sensor output indicates negative pressure, the ECM detects a malfunction in the EVAP canister purge valve, and a DTC is stored.

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There are two conditions when the evaporative emission (EVAP) system will not hold vacuum, and the pressure in the fuel tank doesn't become negative.

1. EVAP system low purge flow.
2. EVAP system leakage or the fuel fill cap is loose/off.

Here is a description of condition 1

The malfunction detection is done during EVAP system leak detection (P0455, P0456).

The engine control module (ECM) monitors the fuel tank pressure (FTP) sensor output. If the FTP sensor output does not indicate the prescribed negative pressure when purging, the ECM detects a malfunction and a DTC is stored.

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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) outputs the "ON" signal to the EVAP canister vent shut valve, the ECM detects a malfunction and a DTC is stored.

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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) outputs the "OFF" signal to the EVAP canister vent shut valve, the ECM detects a malfunction and a DTC is stored.

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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). The ECM 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 detects a malfunction in the idle speed control system and a DTC is stored.

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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). The ECM 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 detects a malfunction in the idle speed control system and a DTC is stored.

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If there is a short to ground in the harness between the engine control module (ECM) and the PGM-FI main relay 1 (FI MAIN), the PGM-FI main relay 1 (FI MAIN) stays ON even though the ignition switch is OFF, and the ECM 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 operates for a set time after the ignition switch is turned OFF, a malfunction is detected and a DTC is stored.

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The multiplex communication is executed among the engine control module (ECM), the gauge assembly unit, and the multiplex control unit.

Each unit transmits a signal to the other units and controls the other unit's use of the necessary information.

When the communication from another unit can not be received for a set time or more, or when an abnormality of the received data occurred a certain number of times, each unit detects a communication abnormality and a DTC is stored.

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

When the ECM 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 stores a DTC that indicates the update is not finished.

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The engine control module (ECM) 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 such as when the battery is disconnected. When power is restored to the ECM, 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.

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

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The engine control module (ECM) 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 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.

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After the ignition switch is turned off, the engine control module (ECM) 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 power is disconnected by controlling PGM-FI main relay 1 (FI MAIN).

During a normal ECM 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 is turned off to shut down the ECM. When the voltage to the ECM is turned off and the ECM 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.

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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.

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

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

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.

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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 (idling) and high signal voltage at low-vacuum (throttle valve wide open).

The engine control module (ECM) 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 detects a malfunction and stores a DTC.

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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).

The engine control module (ECM) 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 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 detects a malfunction and stores a DTC.

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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). 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 the detection of oxygen content by controlling current flow through the heater. The current diminishes as the voltage applied to the element electrode 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 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 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 uses A/F feedback control to issue a Lean command.

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

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If a malfunction causes the air/fuel sensor reading value to the engine control module (ECM) to deviate from the normal control area, the air/fuel ratio (A/F) sensor becomes 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 detects a malfunction and a DTC is stored.

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

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

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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) 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 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).

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

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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 ETCS control relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM).

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. When the ECM receives the malfunction data from the throttle actuator control module, the ECM detects a malfunction in the throttle valve default position spring, and a DTC is stored.

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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 ETCS control relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM).

The throttle valve return spring is attached to the throttle valve gear to return the throttle valve to the default position.

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. When the ECM receives the malfunction data from the throttle actuator control module, the ECM detects a malfunction in the throttle valve return spring and a DTC is stored.

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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 ETCS control relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM).

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 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. When the ECM receives the malfunction data from the throttle actuator control module, the ECM detects the malfunction of the throttle actuator system and a DTC is stored.

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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 ETCS control relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM).

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 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 it 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 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. When the ECM receives the malfunction data from the throttle actuator control module, the ECM detects a malfunction in the throttle actuator control module and stores a DTC. When the ECM monitors the serial signal between the ECM and the throttle actuator control module and these signals do not agree, the ECM detects a malfunction and a DTC is stored.

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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 ETCS control relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM).

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 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.

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. When the ECM receives the malfunction data from the throttle actuator control module, the ECM detects a malfunction of the throttle actuator system and stores a DTC.

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Accelerator pedal position (APP) sensor A is a part of the electronic throttle control system (ETCS), and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM) 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 detects a malfunction and stores a DTC.

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Accelerator pedal position (APP) sensor A is a part of the electronic throttle control system (ETCS), and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM) 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 detects a malfunction and stores a DTC.

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Accelerator pedal position (APP) sensor B is a part of the electronic throttle control system (ETCS), and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM) 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 detects a malfunction and stores a DTC.

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Accelerator pedal position (APP) sensor B is a part of the electronic throttle control system (ETCS), and it is used to convert the position of the accelerator pedal into electrical signals. Based on these signals, the engine control module (ECM) 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 detects a malfunction and stores a DTC.

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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 ETCS control relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM).

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 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 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. When the ECM receives the malfunction data from the throttle actuator control module, the ECM detects a malfunction in the relationship between TP sensor A and TP sensor B, and stores a DTC.

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

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) to compute the target position. The target position signal is 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 of an APP sensor A 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 time, the ECM detects a malfunction, and a DTC is stored.

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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 ETCS control relay, the accelerator pedal position (APP) sensor, and the engine control module (ECM).

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 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 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 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 receives the malfunction data from the throttle actuator control module, the ECM detects a malfunction in the throttle actuator control system and stores a DTC.

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

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.

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The engine coolant temperature (ECT) sensor 2 is a thermistor attached to the radiator. The engine control module (ECM) 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 detects a high signal voltage. As the engine coolant warms, the sensor resistance decreases, and the ECM 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 detects a malfunction and a DTC is stored.

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The engine coolant temperature (ECT) sensor 2 is a thermistor attached to the radiator. The engine control module (ECM) 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 detects a high signal voltage. As the engine coolant warms, the sensor resistance decreases, and the ECM detects a low ECT2 signal voltage.

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

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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 performed 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) detects that the A/F sensor is not properly installed and a DTC is stored.

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The barometric pressure (BARO) sensor is built into the engine control module (ECM) 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 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.

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The barometric pressure (BARO) sensor is built into the engine control module (ECM) and monitors atmospheric pressure. The ECM 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 detects a malfunction and a DTC is stored.

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The barometric pressure (BARO) sensor is built into the engine control module (ECM) and monitors atmospheric pressure. The ECM 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 detects a malfunction and a DTC is stored.

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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 output voltage to the engine control module (ECM). A heater for the sensor element is embedded in the A/F sensor (sensor 1). It heats the sensor to stabilize and speed 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 compares a set target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection duration.

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

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

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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 output voltage to the engine control module (ECM). A heater for the sensor element is embedded in the A/F sensor (sensor 1). It heats the sensor to stabilize and speed the detection of oxygen content. The increase in the 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 compares a set target air/fuel ratio with the detected air/fuel ratio and controls the fuel injection duration.

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

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

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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.

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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.

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The positive crankcase ventilation (PCV) system reduces hydrocarbons (HC). The PCV system recirculates the unburned air/fuel mixture (blow-by vapor) into the intake manifold where it is drawn into the engine and burned, thus reducing HC. If the PCV hose comes off while air is supplied mainly via the idle air control (IAC) valve with the throttle closed, the amount of air supplied to the engine is considerably more than the amount of air the IAC valve supplies.

The engine control module (ECM) estimates the amount of air supplied to the engine while the throttle valve is fully closed, and if the estimated amount is more than the upper limit, it detects a malfunction and a DTC is stored.

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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) monitors the FTP sensor output after purge starts. The ECM 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).

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

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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, 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 and transmitted to the engine control module (ECM) and then to the throttle actuator control module via the circuit. 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 the TP sensors A and B installed in the throttle body.

The ECM 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 set period of time after the throttle actuator control module relay is turned OFF and the throttle actuator control module operation is stopped.

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The engine control module (ECM) 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 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.

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

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

Monitor Execution, Sequence, Duration, DTC Type, OBD Status

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The VTEC system activates the rocker arm oil control solenoid (VTEC solenoid valve) by command from the engine control module (ECM), and it charges/discharges the hydraulic circuit of the VTEC mechanism that switches valve timing between low and high. If the return signal is OFF (low) when the ECM outputs the ON (high) signal to the rocker arm oil control solenoid (VTEC solenoid valve), the ECM detects a malfunction and a DTC is stored.

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The VTEC system activates the rocker arm oil control solenoid (VTEC solenoid valve) by command from the engine control module (ECM), and it charges/discharges the hydraulic circuit of the VTEC mechanism that switches valve timing between low and high. If the return signal is ON (high) when the ECM outputs the OFF (low) signal to the rocker arm oil control solenoid (VTEC solenoid valve), the ECM detects a malfunction and a DTC is stored.

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The air/fuel ratio (A/F) sensor has a linear signal output in relation to the oxygen concentration. The engine control module (ECM) computes the air/fuel ratio from A/F sensor output voltage and uses the fuel feedback control to improve exhaust emissions. The ECM 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.

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The engine control module (ECM) uses the serial signal line to exchange pulsing signals with the throttle actuator control module.

The ECM transmits the accelerator pedal position signal, etc. to the throttle actuator module, and the throttle actuator control module transmits the actual throttle valve position signal, a malfunction signal, etc. to the ECM 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 detects a malfunction and a DTC is stored.

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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) does not receive the signals via the CAN lines for more than a set time, the ECM detects a malfunction and a DTC is stored.

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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) does not receive the signals via the CAN lines for a certain time, the ECM detects a malfunction and a DTC is stored.

MONITOR EXECUTION, SEQUENCE, DURATION, DTC TYPE, OBD STATUS

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