MONITOR DESCRIPTION
The ECM optimizes the valve timing using the VVT system to control the intake camshaft. The VVT system includes the ECM, the OCV and the VVT controller. The ECM sends a target duty-cycle control signal to the OCV. This control signal regulates the oil pressure supplied to the VVT controller. The VVT controller can advance or retard the intake camshaft.
After the ECM sends the target duty-cycle signal to the OCV, the ECM monitors the OCV current to establish an actual duty-cycle. The ECM determines the existence of a malfunction and sets the DTC when the actual duty-cycle ratio varies from the target duty-cycle ratio.
The ECM optimizes the intake valve timing using the VVT (Variable Valve Timing) system to control the intake camshaft. The VVT system includes the ECM, the Oil Control Valve (OCV) and the VVT controller. The ECM sends a target duty-cycle control signal to the OCV. This control signal regulates the oil pressure supplied to the VVT controller. The VVT controller can advance or retard the intake camshaft.
If the difference between the target and actual intake valve timings is large, and changes in actual intake valve timing are small, the ECM interprets this as the VVT controller stuck malfunction and sets a DTC.
Example
A DTC is set when the following conditions 1), 2) and 3) are met
- The difference between the target and actual intake valve timings is more than 5°CA (Crankshaft Angle) and the condition continues for more than 4.5 seconds.
- It takes 5 seconds or more to change the valve timing by 5°CA.
- After above conditions 1) and 2) are met, the OCV is forcibly activated 63 times or more.
DTC P0011 (Advanced Cam Timing) is subject to 1 trip detection logic.
DTC P0012 (Retarded Cam Timing) is subject to 2 trip detection logic.
These DTCs indicate that the VVT controller cannot operate properly due to OCV malfunctions or the presence of foreign objects in the OCV.
The monitor will not run unless the following conditions are met
- The engine is warm (the engine coolant temperature is 75°C [167°F] or more).
- The vehicle has been driven at more than 40 mph (64 km/h) for 3 minutes.
- The engine has idled for 3 minutes.
The ECM optimizes the valve timing by using the VVT (Variable Valve Timing) system to control the intake camshaft. The VVT system includes the ECM, the Oil Control Valve (OCV) and the VVT controller.
The ECM sends a target duty-cycle control signal to the OCV. This control signal regulates the oil pressure supplied to the VVT controller. The VVT controller can advance or retard the intake camshaft. The ECM calibrates the intake valve timing by setting the intake camshaft to the most retarded angle while the engine is idling. The ECM closes the OCV to retard the cam. The ECM stores this value as the VVT learning value. When the difference between the target and actual intake valve timings is 5°CA (Crankshaft Angle) or less, the ECM stores it.
If the learned value meets both of the following conditions, the ECM interprets this as a defect in the VVT system and set a DTC.
- "VVT learning" value is less than 24°CA, or more than 46°CA.
- Above condition continues for 18 seconds or more.
This DTC indicates that the intake camshaft has been installed toward the crankshaft at an incorrect angle, caused by factors such as the timing chain having jumped a tooth.
This monitor begins to run after the engine has idled for 5 minutes.
The ECM uses information from the Heated Oxygen (HO2) sensor to regulate the air-fuel ratio and keep it close to the stoichiometric level. This maximizes the ability of the Three-Way Catalytic Converter (TWC) to purify the exhaust gases.
The HO2 sensor detects oxygen levels in the exhaust gas and transmits the information to the ECM. The inner surface of the sensor element is exposed to outside air. The outer surface of the sensor element is exposed to the exhaust gas. The sensor element is made of platinum coated zirconia and includes an integrated heating element.
The zirconia element generates a small voltage when there is a large difference in the oxygen concentrations between the exhaust gas and outside air. The platinum coating amplifies the voltage generation.
The HO2 sensor is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful voltage signals without supplementary heating. The ECM regulates the supplementary heating using a duty-cycle approach to adjust the average current in the sensor heater element. If the heater current is outside the normal range, the signal transmitted by the HO2 sensor will be inaccurate, as a result, the ECM will be unable to regulate air-fuel ratio properly.
When the current in the HO2 sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and sets a DTC.
Example
The ECM sets either DTC P0032 or P0038 when the current in the HO2 sensor heater is more than 2 A despite the heater being OFF. Conversely, when the heater current is less than 0.25 A despite the heater being ON, DTC P0031 or P0037 is set.
If there is a defect in the MAF meter or an open or short circuit, the voltage level deviates from the normal operating range. The ECM interprets this deviation as a malfunction in the MAF meter and sets a DTC.
Example
When the sensor voltage output remains less than 0.2 V, or more than 4.9 V, for more than 3 seconds, the ECM sets a DTC.
If the malfunction is not repaired successfully, a DTC is set 3 seconds after the engine is next started.
The MAF meter is a sensor that measures the amount of air flowing through the throttle valve. The ECM uses this information to determine the fuel injection time and to provide appropriate air-fuel ratio.
Inside the MAF meter, there is a heated platinum wire which is exposed to the flow of intake air.By applying a specific electrical current to the wire, the ECM heats it to a specific temperature. The flow of incoming air cools both the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, and the ECM uses it to calculate the intake air volume.
If there is a defect in the sensor, or an open or short in the circuit, the voltage level deviates from the normal operating range. The ECM interprets this deviation as a malfunction in the MAF meter and sets the DTC.
Example
If the voltage is more than 2.2 V, or less than 0.93 V while idling, the ECM determines that there is a malfunction in the MAF meter and sets the DTC.
The ECM monitors the sensor voltage and uses this value to calculate the Intake Air Temperature (IAT). When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a malfunction in the IAT sensor and sets a DTC.
Example
If the sensor voltage output is -40°C (-40°F) for 0.5 seconds or more, the ECM determines that there is an open in the IAT sensor circuit, and sets DTC P0113. Conversely, if the voltage output is more than 140°C (284°F) for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit, and sets DTC P0112.
If the malfunction is not repaired successfully, a DTC is set 0.5 seconds after the engine is next started.
The Engine Coolant Temperature (ECT) sensor is used to monitor the ECT. The ECT sensor has a thermistor with a resistance that varies according to the temperature of the engine coolant. When the coolant temperature is low, the resistance in the thermistor increases. When the temperature is high, the resistance drops. These variations in resistance are reflected in the voltage output from the sensor. The ECM monitors the sensor voltage and uses this value to calculate the ECT. When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the ECT sensor and sets a DTC.
Example
If the sensor voltage output is -40°C (-40°F) for 0.5 seconds or more, the ECM determines that there is an open in the ECT sensor circuit, and sets DTC P0118. Conversely, if the voltage output is more than 140°C (284°F) for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit, and sets DTC P0117.
If the malfunction is not repaired successfully, a DTC is set 0.5 seconds after the engine is next started.
The ECT sensor is used to monitor the ECT. The ECT sensor has a built-in thermistor with a resistance that varies according to the temperature of the engine coolant. When the ECT is low, the resistance of the thermistor increases. When the temperature is high, the resistance drops. These variations in the resistance are reflected in the voltage output from the ECT sensor.
The ECM monitors the sensor voltage and uses this value to calculate the ECT. If the sensor voltage output deviates from the normal operating range, the ECM interprets this deviation as a malfunction in the ECT sensor and sets the DTC.
Examples
- Upon starting the engine, the ECT is between 35°C and 60°C (95°F and 140°F). If after driving for 250 seconds, the ECT remains within 3°C (5.4°F) of the staring temperature, the DTC is set (2 trip detection logic).
- Upon starting the engine, the ECT is over 60°C (140°F). If after driving for 250 seconds, the ECM remains within 1 °C (1.8°F) of the starting temperature, the DTC is set (6 trip detection logic).
The resistance of the Throttle Position (TP) sensor varies in accordance with the throttle valve opening angle. The ECM transmits a standardized reference voltage to the +:VC terminal of the TP sensor and calculates the throttle valve opening angle based on the voltage received from the Signal: VTA terminal of the sensor. When the throttle valve is near the fully closed position, the output voltage of the TP sensor is low. When it is near the fully open position, the output voltage is high.
If the ECM detects that the output voltage of the TP sensor is outside the normal range, the ECM interprets this as a malfunction in the TP sensor and sets a DTC.
The resistance of the TP sensor varies in accordance with the throttle valve opening angle. The ECM transmits a standardized reference voltage to the +:VC terminal of the TP sensor and calculates the throttle valve opening angle based on the voltage received from the Signal:VTA terminal of the sensor.
When the throttle valve is near the fully closed position, the output voltage of the TP sensor is low. When it is near the fully open position, the output voltage is high.
The ECM monitors the indicated throttle valve opening angle during stop-and-go driving conditions. If the indicated angle (or voltage) in the closed throttle valve position is outside the specified range, the ECM interprets this as a malfunction in the TP sensor and sets the DTC.
HINT
When this DTC is set, the ECM enters fail-safe mode. During fail-safe mode, the ECM cuts fuel intermittently. Fail-safe mode continues until a pass condition is detected and the ignition switch is turned to OFF.
The resistance of the ECT sensor varies in proportion to the actual ECT. The ECM supplies a constant voltage to the sensor and monitors the signal output voltage of the sensor. The signal voltage output varies according to the changing resistance of the sensor. After the engine is started, the ECT is monitored through this signal. If the ECT sensor indicates that the engine is not yet warm enough for closed-loop fuel control, despite a specified period of time having elapsed since the engine was started, the ECM interprets this as a malfunction in the sensor or cooling system and sets the DTC.
Example
The ECT is 0°C (32°F) at engine start. After 5 minutes running time, the ECT sensor still indicates that the engine is not warm enough to begin closed-loop fuel (air-fuel ratio feedback) control. The ECM interprets this as a malfunction in the sensor or cooling system and sets the DTC.
The ECM uses the front HO2 sensor to optimize the air-fuel ratio with closed-loop fuel control. This control helps to decrease exhaust emissions by keeping the conditions optimum for the TWC to work at maximum efficiency. The front HO2 sensor detects the oxygen level in the exhaust gas, and provides the ECM with feedback to allow it to control the air-fuel ratio accurately.
The front HO2 sensor voltage output ranges from 0 V to 1 V. When the sensor signal voltage is less than 0.45 V, the air-fuel ratio is lean. Conversely, when it is more than 0.45 V, the air-fuel ratio is rich. If the front HO2 sensor does not indicate rich at all despite the closed-loop fuel control conditions being met for a certain period of time, the ECM determines that closed-loop fuel control is malfunctioning. The ECM illuminates the MIL and sets the DTC.
Scheme 1
The ECM monitors the rear Heated Oxygen (HO2) sensor to check for the following malfunctions. If any one of the malfunctions detected, the ECM illuminates the MIL and sets a DTC
- The HO2 sensor output voltage remains above 0.5 V (rich) or below 0.4 V (lean) while the vehicle is accelerated and decelerated for 4 to 8 minutes.
- The HO2 sensor output voltage remains at extremely low, below 0.05 V for a long time period of time while the vehicle is driven.
- The HO2 sensor output voltage remains at extremely low, below 0.2 V (extremely lean condition) soon after fuel-cut is performed while the vehicle is decelerated. The ECM interprets this as the sensor response having deteriorated.
- The HO2 sensor output voltage exceeds more than 1.2 V for 10 seconds.
Under closed-loop fuel control, fuel injection volumes that deviate from those estimated by the ECM cause changes in the long-term fuel trim compensation value. The long-term fuel trim is adjusted when there are persistent deviations in the short-term fuel trim values. Deviations from the ECM's estimated fuel injection volumes also affect the average fuel trim learning value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learning value of the air-fuel ratio). If the average fuel trim learning value exceeds the malfunction thresholds, the ECM interprets this a fault in the fuel system and sets a DTC.
Example
The average fuel trim leaning value is more than +35% or less than -35%, the ECM interprets this as a fuel system malfunction.
Scheme 2
The ECM illuminates the MIL and sets a DTC when either one of the following conditions, which could cause emission deterioration, is detected. (2 trip detection logic.)
- Within the first 1,000 crankshaft revolutions of the engine starting, an excessive misfiring rate (approximately 20 to 50 misfires per 1,000 crankshaft revolutions) occurs once.
- After the first 1,000 crankshaft revolutions, an excessive misfiring rate (approximately 20 to 60 misfires per 1,000 crankshaft revolutions) occurs 4 times in sequential crankshaft revolutions.
The ECM flashes the MIL and sets a DTC when either one of the following conditions, which could cause the Three-Way Catalytic Converter (TWC) damage, is detected. (2 trip detection logic.)
- In every 200 crankshaft revolutions at a high engine rpm, the threshold misfiring percentage is recorded once.
- In every 200 crankshaft revolutions at a normal engine rpm, the threshold misfiring percentage is recorded 3 times.
The knock sensor detects spark knock. When spark knock occurs, the sensor pick-up vibrates in a specific frequency range. When the ECM detects voltage in this frequency range, it retards the ignition timing to suppress the spark knock.
The ECM also senses background engine noise with the knock sensor and uses this noise to check for faults in the sensor. If the knock sensor signal level is too low for more than 10 seconds, and if the knock sensor output voltage is outside the normal range, the ECM interprets this as a malfunction in the sensor and sets the DTC.
If there is no signal from the CKP sensor despite the engine revolving, the ECM interprets this as a malfunction of the sensor.
If the malfunction is not repaired successfully, a DTC is set 10 seconds after the engine is next started.
If no signal is transmitted by the CMP sensor despite the engine revolving, or the rotation of the camshaft and the crankshaft is not synchronized, the ECM interprets this as a malfunction of the sensor.
If the malfunction is not repaired successfully, a DTC is set 10 seconds after the engine is next started.
The ECM uses the two Heated Oxygen (HO2) sensors, mounted in front of and behind the Three-Way Catalytic Converter (TWC), to monitor its efficiency.
The first sensor, Sensor 1, sends pre-catalyst information to the ECM. The second sensor, Sensor 2, sends post-catalyst information to the ECM. The ECM compares the information transmitted by these two sensors to determine the efficiency of the TWC performance and its ability to store oxygen.
When the TWC is functioning properly, the variation in the oxygen concentration in the exhaust gas, after it has passed through the TWC, is small. In this condition, the voltage output of sensor 2 slowly alternates between the rich and lean signal voltages (shown in the illustration below). As the TWC performance efficiency deteriorates, its oxygen storage capacity decreases, and the variation in the oxygen concentration in the exhaust gas increases. As a result, the sensor voltage output fluctuates frequently.
While the catalyst monitor is running, the ECM measures the signal lengths of both sensors 1 and 2, and calculates the ratio of the signal lengths to determine the extent of the TWC deterioration. If the deterioration level exceeds the preset threshold, the ECM interprets this as the TWC malfunction. The ECM then illuminates the MIL and sets the DTC.
This monitor begins to run when the following preconditions apply
Scheme 3
Scheme 4
Scheme 5
- The engine has warmed up (the engine coolant temperature is 75°C [167° F] or more)
- The vehicle has driven at between 37 mph and 63 mph (60 km/h and 100 km/h) for 15 minutes.
The ECM checks the EVAP (Evaporative Emission) system using the vapor pressure sensor, CCV (Canister Closed Valve), and VSV (Vacuum Switching Valve) for EVAP. The ECM closes the EVAP system and introduces negative pressure (a vacuum) into it. The ECM then monitors the internal pressure using the vapor pressure sensor.
The VSV for EVAP is used to discharge the evaporative emissions from the fuel tank into the intake manifold via the canister. In addition, it creates negative pressure (a vacuum) inside the fuel tank simultaneously with the operation of the VSV for CCV to conduct leak tests.
The ECM checks the EVAP (Evaporative Emission) system using the vapor pressure sensor, CCV (Canister Closed valve), and VSV (Vacuum Switching Valve) for EVAP. The ECM closes the EVAP system and introduces negative pressure (a vacuum) into it. The ECM then monitors the internal pressure using the vapor pressure sensor.
see scheme 277
The ECM checks for leaks in the EVAP system by introducing a highly negative pressure from the intake manifold, by signaling the VSV for EVAP to open with the VSV for CCV (vent) closed. After sufficient time has elapsed, the fuel tank develops a highly negative pressure and the VSV for EVAP is then closed. The ECM monitors the pressure rise (vacuum loss) in the fuel tank. If the pressure rapidly rises, the ECM determines that there is a leakage from the EVAP system, and illuminates the MIL and sets a DTC. If the leakage is large, DTC P0442 is set. If it is small, DTC P0456 is set.
Scheme 6
Scheme 7
DTC P0451, P0452 or P0453 is set by the ECM when the vapor pressure sensor malfunctions.
Automatic Transaxle Models
The ECM assumes that the vehicle is being driven, when the indicated engine speed is more than 2,300 rpm and 30 seconds have elapsed since the Park/Neutral Position (PNP) switch was turned OFF. If there is no signal from vehicle speed sensor, despite these conditions being met, the ECM interprets this as a malfunction in the sensor. The ECM then illuminates the MIL and sets the DTC.
Manual Transaxle Models
The ECM assumes that the vehicle is being driven, while the vehicle speed sensor signal is being transmitted by the combination meter. If there is no signal from the vehicle speed sensor despite this condition being met, the ECM interprets this as a malfunction in the sensor. The ECM then illuminates the MIL and sets the DTC.
The ECM monitors the sensor voltage and uses this value to regulates the engine idling speed. When the sensor output voltage deviates from the normal operating range, the ECM determines that there is a malfunction in the power steering oil pressure sensor and sets a DTC.
The battery supplies electricity to the ECM even when the ignition switch is in the OFF position. This power allows the ECM to store data such as DTC history, freeze frame data and fuel trim values. If the battery voltage falls below a minimum level, these memories are cleared and the ECM determines that there is a malfunction in the power supply circuit. When the engine is next started, the ECM illuminates the MIL and sets the DTC.
Scheme 8
HINT
If DTC P0560 is set, the ECM does not store other DTCs.
The ECM continuously monitors its own internal circuits. This self-checking ensures that the ECM is functioning properly.
The two CPUs, main and sub, inside the ECM, perform continuous mutual monitoring. If the outputs from the two CPUs differ or deviate from the standard levels, the ECM determines that the internal circuits are malfunctioning. The ECM then illuminates the MIL and sets the DTC.
| DTC No. | DTC Detection Conditions | Trouble Areas |
|---|---|---|
| P0606 | ECM internal error (1 trip detection logic) | ECM |
DTC DETECTION CONDITIONS
While the engine being cranked, the positive battery voltage is applied to terminal STA of the ECM.
If the ECM detects the Starter Control (STA) signal while the vehicle is being driven, it determines that there is a malfunction in the STA circuit. The ECM then illuminates the MIL and sets the DTC.
This monitor runs when the vehicle is driven at 12.4 mph (20 km/h) for over 20 seconds.
