Engine Control System (Diagnostic Codes (P0010 - P0198)) (2ZR-FAE): Overview Toyota Corolla XI

DESCRIPTION

The Variable Valve Timing (VVT) system adjusts the intake valve timing to improve driveability. The engine oil pressure turns the VVT controller to adjust the valve timing.

The camshaft timing oil control valve assembly is a solenoid valve and switches the engine oil line. The valve moves when the ECM applies 12 V to the solenoid. The ECM changes the energizing time to the solenoid (duty-cycle) in accordance with the camshaft position, crankshaft position, throttle position, etc.

Scheme 128

MONITOR DESCRIPTION

This DTC is designed to detect an open or short in the camshaft timing oil control valve assembly (for intake camshaft) circuit. If the camshaft timing oil control valve assembly duty-cycle is excessively high or low while the ignition switch is ON or the engine is running, the ECM will illuminate the MIL and store this DTC.

Refer to DTC P0010.

Refer to DESCRIPTION

The ECM optimizes the intake valve timing using the Variable Valve Timing (VVT) system to control the intake camshaft. The VVT system includes the ECM, the camshaft timing oil control valve assembly (for intake camshaft) and the VVT controller (camshaft timing gear assembly). The ECM sends a target duty-cycle control signal to the camshaft timing oil control valve assembly (for intake camshaft). 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 timing is large, and changes in the actual intake valve timing are small, the ECM interprets this as a VVT controller stuck malfunction and stores a DTC.

1. Example
2. A DTC is stored when the following conditions "A" and "B" are met: It takes 5 seconds or more to change the valve timing by 5°CA (Condition "A"). After the condition "A" is met, the camshaft timing oil control valve assembly (for intake camshaft) is forcibly activated for 10 seconds (Condition "B").

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 a camshaft timing oil control valve assembly (for intake camshaft) malfunction or the presence of foreign matter in the camshaft timing oil control valve assembly (for intake camshaft).

The Variable Valve Timing (VVT) system adjusts the exhaust valve timing to improve driveability. The engine oil pressure turns the VVT controller to adjust the valve timing.

The camshaft timing oil control valve assembly is a solenoid valve and switches the engine oil line. The valve moves when the ECM applies 12 V to the solenoid. The ECM changes the energizing time to the solenoid (duty-cycle) in accordance with the camshaft position, crankshaft position, throttle position, etc.

Scheme 129

This DTC is designed to detect an open or short in the camshaft timing oil control valve assembly (for exhaust camshaft) circuit. If the camshaft timing oil control valve assembly duty-cycle is excessively high or low while the ignition switch is ON or the engine is running, the ECM will illuminate the MIL and store this DTC.

Refer to DTC P0013.

Refer to DESCRIPTION

The ECM optimizes the exhaust valve timing using the Variable Valve Timing (VVT) system to control the exhaust camshaft. The VVT system includes the ECM, the camshaft timing oil control valve assembly (for exhaust camshaft) and the VVT controller (camshaft timing exhaust gear assembly). The ECM sends a target duty-cycle control signal to the camshaft timing oil control valve assembly (for exhaust camshaft). This control signal regulates the oil pressure supplied to the VVT controller. The VVT controller can advance or retard the exhaust camshaft.

If the difference between the target and actual exhaust valve timing is large, and changes in the actual exhaust valve timing are small, the ECM interprets this as a VVT controller stuck malfunction and stores a DTC.

1. Example
2. A DTC is stored when the following conditions "A" and "B" are met: It takes 5 seconds or more to change the valve timing by 5°CA (Condition "A"). After the condition "A" is met, the camshaft timing oil control valve assembly (for exhaust camshaft) is forcibly activated for 10 seconds (Condition "B").

DTC P0014 (Advanced Cam Timing) is subject to 2 trip detection logic.

DTC P0015 (Retarded Cam Timing) is subject to 1 trip detection logic.

These DTCs indicate that the VVT controller cannot operate properly due to a camshaft timing oil control valve assembly (for exhaust camshaft) malfunction or the presence of foreign matter in the camshaft timing oil control valve assembly (for exhaust camshaft).

In the VVT (Variable Valve Timing) system, the appropriate intake and exhaust valve open and close timing is controlled by the ECM. The ECM performs intake and exhaust valve control by performing the following: 1) controlling the camshaft and camshaft timing oil control valve assembly, and operating the camshaft timing gear; and 2) changing the relative positions of the camshaft and crankshaft.

To monitor the correlation of the intake camshaft position and crankshaft position, the ECM checks the VVT learned value while the engine is idling. The VVT learned value is calibrated based on the camshaft position and crankshaft position. The intake valve timing is set to the most retarded angle while the engine is idling. If the VVT learned value is out of the specified range in consecutive driving cycles, the ECM illuminates the MIL and stores DTC P0016.

To monitor the correlation of the exhaust camshaft position and crankshaft position, the ECM checks the VVT learned value while the engine is idling. The VVT learned value is calibrated based on the camshaft position and crankshaft position. The exhaust valve timing is set to the most advanced angle while the engine is idling. If the VVT learned value is out of the specified range in consecutive driving cycles, the ECM illuminates the MIL and stores DTC P0017.

Refer to DTC P2195.

Refer to DESCRIPTION

HINT

Scheme 130

1. When any of these DTCs are stored, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned off.
2. Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
3. The ECM has a pulse width modulated control circuit to adjust the current through the heater. The air fuel ratio sensor heater circuit uses a relay on the +B side of the circuit.

The ECM uses information from the air fuel ratio 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 to purify the exhaust gases.

The air fuel ratio 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 the 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 this voltage generation.

The air fuel ratio 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 air fuel ratio sensor becomes inaccurate. As a result, the ECM is unable to regulate the air fuel ratio properly.

When the current in the air fuel ratio sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.

Refer to DTC P0136.

Refer to DESCRIPTION

HINT

When any of these DTCs are stored, the ECM enters fail-safe mode. The ECM turns off the heated oxygen sensor heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned off.

Scheme 131

The sensing portion of the heated oxygen sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature, and the difference between the oxygen concentrations surrounding the inside and outside surfaces of the sensor is large, the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor.

Heated Oxygen Sensor Heater Range Check (P0037 or P0038)

1. The ECM monitors the current applied to the heated oxygen sensor heater to check the heater for malfunctions. If the heater current is outside the normal range, the signal transmitted by the heated oxygen sensor becomes inaccurate. When the current in the heated oxygen sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and stores a DTC.

Heated Oxygen Sensor Heater Performance (P0141)

1. After the accumulated heater on time exceeds 100 seconds, the ECM calculates the heater resistance using battery voltage and the current applied to the heater. If the resistance is above the threshold value, the ECM determines that there is a malfunction in the heated oxygen sensor heater and stores DTC P0141.

Refer to DTC P0102.

Refer to DESCRIPTION

The mass air flow meter sub-assembly is a sensor that measures the amount of air flowing through the throttle valve. The ECM uses this information to determine fuel injection timing and to provide an appropriate air fuel ratio. Inside the mass air flow meter sub-assembly, 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, the ECM varies the voltage applied to the mass air flow meter sub-assembly. The voltage level is proportional to the airflow through the sensor, and the ECM uses it to calculate the intake air volume.

The ECM monitors the average engine load value ratio to check the mass air flow meter sub-assembly for malfunctions. The average engine load value ratio is obtained by comparing the average engine load calculated from the mass air flow meter sub-assembly output to the average engine load estimated from the driving conditions, such as the engine speed and the throttle opening angle. If the average engine load value ratio is below the threshold value, the ECM determines that the intake air volume is low, and if the average engine load value ratio is above the threshold value, the ECM determines that the intake air volume is high.

If this is detected in 2 consecutive driving cycles, the MIL is illuminated and a DTC is stored.

The mass air flow meter sub-assembly is a sensor that measures the amount of air flowing through the throttle valve. The ECM uses this information to determine the fuel injection duration and to provide an appropriate air fuel ratio. Inside the mass air flow meter sub-assembly, 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, the ECM varies the voltage applied to the wire and internal thermistor. The voltage level is proportional to the airflow through the sensor, and the ECM uses it to calculate the intake air volume.

The circuit is constructed so that the platinum hot wire and the temperature sensor create a bridge circuit, and the power transistor is controlled so that the potentials of A and B remain equal to maintain the predetermined temperature.

HINT

When any of these DTCs are stored, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the ECM, according to the engine speed and throttle valve position. Fail-safe mode continues until a pass condition is detected.

Scheme 132

HINT

When any of these DTCs are output, check the air flow rate by using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / MAF.

If there is a defect or an open or short circuit in the mass air flow meter sub-assembly, the voltage level deviates from the normal operating range. The ECM interprets this deviation as a malfunction in the mass air flow meter sub-assembly circuit and stores a DTC.

Example

When the sensor output voltage remains less than 0.2 V, or higher than 4.9 V for 3 seconds, the ECM stores a DTC.

When the intake manifold pressure measured after engine start drops by less than 3 kPa(abs) [22.5 mmHg(abs)] compared to the intake manifold pressure (atmospheric pressure) measured before engine start, the ECM interprets this as a malfunction in the manifold absolute pressure sensor and stores DTC P0106.

Refer to DTC P0106.

Refer to DESCRIPTION

HINT

When any of these DTCs are output, check the manifold absolute pressure using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Primary / MAP.

The ECM monitors the manifold absolute pressure sensor voltage and uses this value to calculate the intake manifold pressure. When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a malfunction in the manifold absolute pressure sensor and stores a DTC.

Example

When the sensor output voltage is less than 0.5 V, or higher than 4.5 V for 0.5 seconds, the ECM stores a DTC.

Refer to DTC P0112.

Refer to DESCRIPTION

The ECM performs OBD II monitoring based on the values from the intake air temperature sensor. If there is no change of the sensor value within the normal range, the ECM will not be able to perform OBD II monitoring or will misdiagnose that there is a malfunction in the sensor. The ECM detects when the intake air temperature sensor value is stuck by performing monitoring after the ignition switch is turned off or the engine is started (short soak or long soak).

The ECM monitors the sensor voltage and uses this value to calculate the intake air temperature. When the sensor output voltage deviates from the normal operating range, the ECM interprets this as a malfunction in the intake air temperature sensor circuit and stores a DTC.

Example

If the sensor output voltage is higher than 4.91 V for 0.5 seconds or more, the ECM determines that there is an open in the intake air temperature sensor circuit, and stores DTC P0113. Conversely, if the output voltage is less than 0.18 V for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit, and stores DTC P0112.

A thermistor, whose resistance value varies according to the engine coolant temperature, is built into the engine coolant temperature sensor. The structure of the sensor and its connection to the ECM are the same as those of the intake air temperature sensor.

HINT

When DTC P0115, P0117 or P0118 is stored, the ECM enters fail-safe mode. During fail-safe mode, the engine coolant temperature is estimated to be 80°C (176°F) by the ECM. Fail-safe mode continues until a pass condition is detected.

HINT

When any of these DTCs are output, check the engine coolant temperature using the Techstream. Enter the following menus on the Techstream: Powertrain / Engine and ECT / Data List / Primary / Coolant Temp.

The engine coolant temperature sensor is used to monitor the engine coolant temperature. The engine coolant temperature 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 output voltage from the sensor. The ECM monitors the sensor voltage and uses this value to calculate the engine coolant temperature. If the sensor output voltage deviates from the normal operating range, the ECM interprets this as a fault in the engine coolant temperature sensor circuit and stores a DTC.

Example

If the sensor output voltage is higher than 4.91 V for 0.5 seconds or more, the ECM determines that there is an open in the engine coolant temperature sensor circuit, and stores DTC P0118. Conversely, if the voltage output is less than 0.14 V for 0.5 seconds or more, the ECM determines that there is a short in the sensor circuit, and stores DTC P0117.

Refer to DTC P0115.

Refer to DESCRIPTION

Engine Coolant Temperature Sensor Cold Start Monitor

When a cold engine start is performed and then the engine is warmed up, if the engine coolant temperature sensor value does not change, it is determined that a malfunction has occurred. If this is detected in 2 consecutive driving cycles, the MIL is illuminated and this DTC is stored.

Engine Coolant Temperature Sensor Soak Monitor

If the engine coolant temperature sensor value does not change after the warmed up engine is stopped and then the next cold engine start is performed, it is determined that a malfunction has occurred. If this is detected in 2 consecutive driving cycles, the MIL is illuminated and this DTC is stored.

The engine has two temperature sensors, an engine coolant temperature sensor and an intake air temperature sensor, to detect temperature while the engine is operating. A thermistor, whose resistance value varies according to the temperature, is built into each sensor. When the temperature becomes low, the resistance of the thermistor increases. When the temperature becomes high, the resistance drops. These variations in resistance are transmitted to the ECM as voltage changes. Based on these temperature signals output from the sensors, the ECM determines the fuel injection duration and the ignition timing to control the engine.

Scheme 133

HINT

1. Waiting is required to prevent the temperature of the engine from affecting the readings. If the engine has been operated recently, it is not possible to accurately compare the readings.

1. For diagnosis, in order to duplicate the detection conditions of the DTC, it is necessary to park the vehicle for 7 hours. Parking the vehicle for 7 hours ensures that the actual temperature of the engine coolant temperature and intake air temperature are very similar. When the vehicle has been parked for less than 7 hours, differences in the readings may exist, but this does not necessarily indicate a fault.

The ECM monitors the difference between the engine coolant temperature and the intake air temperature when the engine is started cold to accurately detect the engine temperature conditions. The monitor runs when the engine is started after 7 hours or more have elapsed since the engine was stopped (ignition switch turned off) on the previous trip. If the difference between the engine coolant temperature and the intake air temperature on a cold start exceeds 28.125°C (50.625°F), the ECM interprets this as a malfunction in the engine coolant temperature sensor circuit and intake air temperature sensor circuit, and stores this DTC.

HINT

These DTCs relate to the throttle position sensor.

The throttle position sensor is mounted on the throttle body assembly and detects the opening angle of the throttle valve. This sensor is a non-contact type sensor. It uses Hall-effect elements in order to yield accurate signals even in extreme driving conditions, such as at high speeds as well as very low speeds.

The throttle position sensor has 2 sensor circuits, VTA1 and VTA2 each of which transmits a signal. VTA1 is used to detect the throttle valve angle and VTA2 is used to detect malfunctions in VTA1. The sensor signal voltages vary between 0 V and 5 V in proportion to the throttle valve opening angle, and are transmitted to the VTA1 and VTA2 terminals of the ECM.

As the valve closes, the sensor output voltage decreases and as the valve opens, the sensor output voltage increases. The ECM calculates the throttle valve opening angle according to these signals and controls the throttle actuator in response to driver inputs. These signals are also used in calculations such as air fuel ratio correction, power increase correction and fuel-cut control.

Scheme 134

HINT

1. When any of these DTCs are output, check the throttle valve opening angle using the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Gas Throttle / Throttle Position No. 1 and Throttle Position No. 2.

1. Throttle Position No. 1 is the VTA1 signal, and Throttle Position No. 2 is the VTA2 signal. Reference (Normal Condition) Techstream Display Accelerator Pedal Fully Released Accelerator Pedal Fully Depressed Throttle Position No. 1 0.5 to 1.1 V 3.2 to 4.8 V Throttle Position No. 2 2.1 to 3.1 V 4.6 to 4.98 V

The ECM uses the throttle position sensor to monitor the throttle valve opening angle. There are several checks that the ECM performs to confirm the proper operation of the throttle position sensor.

P0120, P0122, P0123, P0220, P0222, P0223 and P2135

1. A specific voltage difference is expected between the sensor terminals, VTA1 and VTA2, for each throttle valve opening angle. If the difference between VTA1 and VTA2 is incorrect, the ECM interprets this as a malfunction in the sensor circuit, and stores a DTC.
2. VTA1 and VTA2 each have a specific voltage range. If VTA1 or VTA2 is outside the normal operating range, the ECM interprets this as a malfunction in the sensor circuit, and stores a DTC.
3. VTA1 and VTA2 should never be close to the same voltage level. If VTA1 is within 0.02 V of VTA2, the ECM determines that there is a short in the sensor circuit, and stores a DTC.

P0121

1. This sensor transmits two signals: VTA1 and VTA2. VTA1 is used to detect the throttle opening angle and VTA2 is used to detect malfunctions in VTA1. The ECM performs several checks to confirm the proper operation of the throttle position sensor and VTA1. For each throttle opening angle, a specific voltage difference is expected between the outputs of VTA1 and VTA2. If the output voltage difference between the two signals deviates from the normal operating range, the ECM interprets this as a malfunction in the throttle position sensor. In this case the ECM will illuminate the MIL and store this DTC.

Refer to DTC P0115.

Refer to DESCRIPTION

The resistance of the engine coolant temperature sensor varies in proportion to the actual engine coolant temperature. The ECM supplies a constant voltage to the sensor and monitors the signal output voltage of the sensor. The signal output voltage varies according to the changing resistance of the sensor. After the engine is started, the engine coolant temperature is monitored by this signal. If the engine coolant temperature 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 stores this DTC.

HINT

This DTC relates to the thermostat.

This DTC is stored when the engine coolant temperature does not reach 73°C (163.4°F) despite sufficient engine warm-up time having elapsed.

Scheme 135

The ECM estimates the engine coolant temperature based on the starting temperature, engine load, and engine speed. The ECM then compares the estimated temperature with the actual engine coolant temperature. When the estimated engine coolant temperature reaches 73°C (163.4°F), the ECM checks the actual engine coolant temperature. If the actual engine coolant temperature is less than 73°C (163.4°F), the ECM interprets this as a malfunction in the thermostat or the engine cooling system and stores this DTC.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC (Three-Way Catalytic Converter) is used. For the most efficient use of the TWC, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric air fuel level. For the purpose of helping the ECM to deliver accurate air fuel ratio control, a heated oxygen sensor is used.

The heated oxygen sensor is located behind the TWC, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).

When the air fuel ratio becomes lean, the oxygen concentration in the exhaust gas is high. The heated oxygen sensor informs the ECM that the post-TWC air fuel ratio is lean (low voltage, i.e. less than 0.45 V).

Conversely, when the air fuel ratio is richer than the stoichiometric air fuel level, the oxygen concentration in the exhaust gas is low. The heated oxygen sensor informs the ECM that the post-TWC air fuel ratio is rich (high voltage, i.e. higher than 0.45 V). The heated oxygen sensor has the property of changing its output voltage drastically when the air fuel ratio is close to the stoichiometric level.

The ECM uses the supplementary information from the heated oxygen sensor to determine whether the air fuel ratio after the TWC is rich or lean, and adjusts the fuel injection duration accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air fuel ratio control.

Scheme 136

Scheme 137

Scheme 138

Scheme 139

1. Active Air Fuel Ratio Control The ECM usually performs air fuel ratio feedback control so that the air fuel ratio sensor output indicates a near stoichiometric air fuel level. This vehicle includes active air fuel ratio control in addition to regular air fuel ratio control. The ECM performs active air fuel ratio control to detect any deterioration in the Three-Way Catalytic Converter (TWC) and heated oxygen sensor malfunctions (refer to the diagram below). Active air fuel ratio control is performed for approximately 15 to 20 seconds while driving with a warm engine. During active air fuel ratio control, the air fuel ratio is forcibly regulated to become lean or rich by the ECM. If the ECM detects a malfunction, a DTC is stored.
2. Abnormal Voltage Output of Heated Oxygen Sensor (DTC P0136) While the ECM is performing active air fuel ratio control, the air fuel ratio is forcibly regulated to become rich or lean. If the sensor is not functioning properly, the voltage output variation is small. For example, when the heated oxygen sensor voltage does not increase to 0.66 V or higher during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormal and stores DTC P0136.
3. Open in Heated Oxygen Sensor Circuit (DTC P0137) During active air fuel ratio control, the ECM calculates the Oxygen Storage Capacity (OSC)* of the Three-Way Catalytic Converter (TWC) by forcibly regulating the air fuel ratio to become rich or lean. If the heated oxygen sensor has an open circuit, or the voltage output of the sensor noticeably decreases, the OSC indicates an extraordinarily high value. Even if the ECM attempts to continue regulating the air fuel ratio to become rich or lean, the heated oxygen sensor output does not change. While performing active air fuel ratio control, when the target air fuel ratio is rich and the heated oxygen sensor voltage output is less than 0.21 V (lean), the ECM interprets this as an abnormally low sensor output voltage and stores DTC P0137. HINT: *: The TWC has the capability to store oxygen. The OSC and the emission purification capacity of the TWC are mutually related. The ECM determines whether the catalyst has deteriorated, based on the calculated OSC value. Refer to «MONITOR DESCRIPTION»(ref-635601-S00705281482014070300000)
4. High or Low Impedance of Heated Oxygen Sensor (DTC P0136 or P0137) During normal air fuel ratio feedback control, there are small variations in the exhaust gas oxygen concentration. In order to continuously monitor the slight variation of the heated oxygen sensor signal while the engine is running, the impedance* of the sensor is measured by the ECM. The ECM determines that there is a malfunction in the sensor when the measured impedance deviates from the standard range. *: The effective resistance in an alternating current electrical circuit. HINT: The impedance cannot be measured using an ohmmeter. DTC P0136 indicates the deterioration of the heated oxygen sensor. The ECM stores the DTC by calculating the impedance of the sensor when the typical enabling conditions are satisfied (2 trip detection logic). DTC P0137 indicates an open or short circuit in the heated oxygen sensor (2 trip detection logic). The ECM stores the DTC when the impedance of the sensor exceeds the threshold 15 kohms.
5. Extremely High Output Voltage of Heated Oxygen Sensor (DTC P0138) The ECM continuously monitors the heated oxygen sensor output voltage while the engine is running. DTC P0138 is stored if the heated oxygen sensor voltage output is 1.2 V or higher for 10 seconds or more.
6. Abnormal Voltage Output of Heated Oxygen Sensor During Fuel-cut (DTC P0139) The sensor output voltage drops to less than 0.2 V (extremely lean status) immediately when the vehicle decelerates and fuel cut is operating. If the voltage does not drop to less than 0.2 V for 7 seconds or more, the system determines that the sensor response has deteriorated, illuminates the MIL and stores DTC P0139.
7. Abnormal Voltage Output of Heated Oxygen Sensor During Fuel-cut from Rich Condition (DTC P013A) If the sensor output voltage does not drop from 0.35 to 0.2 V immediately when the vehicle decelerates and fuel cut is operating, the ECM illuminates the MIL and stores DTC P013A.

Refer to DTC P2195.

Refer to DESCRIPTION

*: Calculated by the ECM based on the air fuel ratio sensor output.

After the engine has been warmed up, the ECM carries out air fuel ratio feedback control and maintains the air fuel ratio at the stoichiometric level. In addition, after all the preconditions have been met, active air fuel ratio control is carried out for approximately 15 to 20 seconds, and during active air fuel ratio control, the ECM measures the response of the air fuel ratio sensor by increasing or decreasing the injection volume by a specific quantity based on the stoichiometric air fuel ratio learned during normal air fuel control. The ECM determines whether there is an air fuel ratio sensor malfunction at the mid-point of active air fuel ratio control.

If the air fuel ratio sensor's response ability is reduced, DTC P014C and P014D are stored.

If the time it takes the air fuel ratio sensor output to change is delayed, DTC P015A and P015B are stored.

Scheme 140

The fuel trim is related to the feedback compensation value, not to the basic injection duration. The fuel trim consists of both the short-term and long-term fuel trims.

The short-term fuel trim is fuel compensation that is used to constantly maintain the air fuel ratio at stoichiometric levels. The signal from the air fuel ratio sensor indicates whether the air fuel ratio is rich or lean compared to the stoichiometric ratio. This triggers a reduction in the fuel injection volume if the air fuel ratio is rich and an increase in the fuel injection volume if lean.

Factors such as individual engine differences, wear over time and changes in operating environment cause short-term fuel trim to vary from the central value. The long-term fuel trim, which controls overall fuel compensation, compensates for long-term deviations in the fuel trim from the central value caused by the short-term fuel trim compensation.

HINT

1. When DTC P0171 is stored, the actual air fuel ratio is on the lean side. When DTC P0172 is stored, the actual air fuel ratio is on the rich side.
2. If the vehicle runs out of fuel, the air fuel ratio is lean and DTC P0171 may be stored. The MIL is then illuminated.
3. When the total of the short-term and long-term fuel trim values is within the malfunction threshold (and the engine coolant temperature is higher than 75°C [167°F]), the system is functioning normally.

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 fuel injection volumes estimated by the ECM also affect the average fuel trim learned value, which is a combination of the average short-term fuel trim (fuel feedback compensation value) and the average long-term fuel trim (learned value of the air fuel ratio). If the average fuel trim learned value exceeds the malfunction thresholds, the ECM interprets this as a fault in the fuel system and stores a DTC.

Example

The average fuel trim learned value is +35% or higher, or -35% or less, the ECM interprets this as a fuel system malfunction.

Scheme 141

A thermistor, whose resistance changes in accordance with the engine oil temperature, is built into the engine oil temperature sensor. As the engine oil temperature decreases, the thermistor resistance increases and as the engine oil temperature increases, the thermistor resistance decreases. The engine oil temperature sensor is connected to the ECM. A voltage of 5 V is supplied from terminal THEO via resistor R of the ECM. Since resistor R and the engine oil temperature sensor are connected in series, both the resistance and the electrical potential of THEO are subject to change in accordance with a change in the engine oil temperature.

The ECM uses the engine oil temperature sensor voltage to calculate the engine oil temperature. If the ECM detects that the output from the sensor deviates from the standard range, the ECM determines that the engine oil temperature sensor has malfunctioned and stores DTC P0196.

Refer to DTC P0196.

Refer to DESCRIPTION

The ECM monitors the engine oil temperature sensor and uses the sensor voltage to calculate the engine oil temperature. If the output voltage from the sensor deviates from the standard range, the ECM determines that the engine oil temperature sensor has malfunctioned and stores a DTC.

Example

If the engine oil temperature sensor output voltage is higher than 4.95 V for 3 seconds or more, the ECM determines that the engine oil temperature sensor circuit is open and stores DTC P0198. If the engine oil temperature sensor output voltage is less than 0.05 V for 3 seconds or more, the ECM determines that the engine oil temperature sensor circuit is shorted and stores DTC P0197.

See also:
• ON-VEHICLE INSPECTION [08/2013 - ]
• PROCEDURE - Step 2
• PROCEDURE - Step 1