Engine Control (Diagnostic Codes (P0010-P0420): Overview Lexus HS I

DESCRIPTION

The VVT (variable valve timing) 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 (included in hybrid vehicle control ECU) applies 12 V to the solenoid. The hybrid vehicle control ECU changes the energizing time to the solenoid (duty-cycle) in accordance with the camshaft position, crankshaft position, throttle position, etc.

Scheme 121

MONITOR DESCRIPTION

This DTC is designed to detect open or short circuits in the camshaft timing oil control valve assembly circuit. If the camshaft timing oil control valve's duty-cycle is excessively high or low while the engine is running, the hybrid vehicle control ECU will illuminate the MIL and set the DTC.

Refer to DTC P0010. Refer to DESCRIPTION .

The hybrid vehicle control ECU optimizes the intake valve timing using the VVT (Variable Valve Timing) system to control the intake camshaft. The VVT system includes the hybrid vehicle control ECU, the camshaft timing oil control valve assembly and the VVT controller. The hybrid vehicle control ECU sends a target duty-cycle control signal to the camshaft timing oil control valve assembly. 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 hybrid vehicle control ECU interprets this as a VVT controller stuck malfunction and sets a DTC.

1. Example
2. A DTC is set 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 above condition is met, the camshaft timing oil control valve is forcibly activated for 10 seconds (Condition "B").
3. The monitor will run if all of 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 47 mph (75 km/h) for 5 minutes. The engine has idled for 3 minutes.
4. DTC P0011 (Advanced Cam Timing) is subject to 1 trip detection logic.
5. DTC P0012 (Retarded Cam Timing) is subject to 2 trip detection logic.
6. These DTCs indicate that the VVT controller cannot operate properly due to camshaft timing oil control valve assembly malfunctions or the presence of foreign objects in the camshaft timing oil control valve assembly.

The hybrid vehicle control ECU optimizes the valve timing by using the VVT (Variable Valve Timing) system to control the intake camshaft. The VVT system includes the hybrid vehicle control ECU, the camshaft timing oil control valve assembly and the VVT controller (camshaft timing gear assembly). The hybrid vehicle control ECU sends a target duty-cycle control signal to the camshaft timing oil control valve assembly.

This control signal regulates the oil pressure supplied to the VVT controller. The VVT controller can advance or retard the intake camshaft.

To monitor the correlation of the intake camshaft position and crankshaft position, the hybrid vehicle control ECU checks the VVT learning value while the engine is idling. The VVT learning 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 learning value is out of specified range in consecutive driving cycles, the hybrid vehicle control ECU illuminates the MIL and sets the DTC P0016.

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.

Refer to DTC P2195. Refer to DESCRIPTION .

HINT

Scheme 122

1. When any of these DTCs is set, the hybrid vehicle control ECU enters fail-safe mode. The hybrid vehicle control ECU turns off the air fuel ratio sensor heater in fail-safe mode. Fail-safe mode continues until the power switch is turned off.
2. Although the DTC titles say the oxygen sensor, these DTCs relate to the air fuel ratio sensor.
3. Bank 1 sensor 1 refers to the sensor mounted in front of the Three-way catalytic converter and located near the engine assembly.
4. The hybrid vehicle control ECU uses pulse width modulation to adjust the current through the heater. The air fuel ratio sensor heater circuit uses a relay on the +B side of the circuit.

HINT

1. Bank 1 sensor 1 refers to the sensor closest to the engine assembly.
2. Bank 1 sensor 2 refers to the sensor farthest away from the engine assembly.

The hybrid vehicle control ECU 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 hybrid vehicle control ECU. 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 hybrid vehicle control ECU 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 hybrid vehicle control ECU is unable to regulate air fuel ratio properly.

When the current in the air fuel ratio sensor heater is outside the normal operating range, the hybrid vehicle control ECU interprets this as a malfunction in the sensor heater and sets a DTC.

Refer to DTC P0136. Refer to DESCRIPTION .

HINT

Scheme 123

1. Sensor 2 refers to the sensor mounted behind the three-way catalytic converter and located far from the engine assembly.
2. When any of these DTCs are set, the hybrid vehicle control ECU enters fail-safe mode. The hybrid vehicle control ECU turns off the heated oxygen sensor heater in fail-safe mode. Fail-safe mode continues until the power switch is turned off.
3. The hybrid vehicle control ECU uses pulse width modulation to adjust the current through the heater. The heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.

HINT

1. Bank 1 sensor 1 refers to the sensor closest to the engine assembly.
2. Bank 1 sensor 2 refers to the sensor farthest away from the engine assembly.

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 hybrid vehicle control ECU supplements the heat from the exhaust with heat from a heating element inside the sensor.

Heated Oxygen Sensor Heater Range Check (P0037, P0038 and P102D)

1. The hybrid vehicle control ECU 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 hybrid vehicle control ECU 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 hybrid vehicle control ECU calculates the heater resistance using battery voltage and the current applied to the heater. If the resistance is above the threshold value, the hybrid vehicle control ECU 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 is a sensor that measures the amount of air flowing through the throttle valve. The hybrid vehicle control ECU uses this information to determine the fuel injection time and to provide an appropriate air fuel ratio. Inside the mass air flow 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 hybrid vehicle control ECU 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 hybrid vehicle control ECU varies the voltage applied to these components of the mass air flow meter. The voltage level is proportional to the airflow through the sensor, and the hybrid vehicle control ECU uses it to calculate the intake air volume.

The hybrid vehicle control ECU monitors the average engine load value ratio to check the mass air flow meter for malfunctions. The average engine load value ratio is obtained by comparing the average engine load calculated from the mass air flow meter 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 hybrid vehicle control ECU determines that the intake air volume is low, and if the average engine load value ratio is above the threshold value, the hybrid vehicle control ECU 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 set.

The mass air flow meter sub-assembly is a sensor that measures the amount of air flowing through the throttle valve.

The hybrid vehicle control ECU uses this information to determine the fuel injection time and to provide the 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 flow of incoming air cools both the wire and an internal thermistor, affecting their resistance. To maintain a constant temperature value of the hot wire, current is applied to these components in the mass air flow meter sub-assembly. The voltage level is proportional to the airflow through the sensor, and the hybrid vehicle control ECU 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 either of these DTCs are set, the hybrid vehicle control ECU enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the hybrid vehicle control ECU, according to the engine speed and throttle valve position. Fail-safe mode continues until a pass condition is detected.

Scheme 124

HINT

When any of these DTCs are set, check the air-flow rate by entering the following menus: Powertrain / Engine and ECT / Data List / MAF.

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

Example

When the sensor output voltage remains less than 0.2 V, or more than 4.9 V, for more than 3 seconds, the hybrid vehicle control ECU sets a DTC.

If the malfunction is not repaired successfully, a DTC is set 3 seconds after the engine is next started.

The manifold absolute pressure sensor detects pressure inside the intake manifold as an absolute pressure with a built-in sensor and outputs a voltage. Based on the voltage from the manifold absolute pressure sensor, the hybrid vehicle control ECU controls the purge VSV and detects errors in the pressure sensor using the changes in pressure.

Scheme 125

The manifold absolute pressure sensor detects the intake manifold pressure as a voltage using a built-in sensor. The ECM calculates intake manifold pressure based on this voltage and also calculates the purge VSV opening amount according to changes in the intake manifold pressure. When the intake manifold pressure measured after engine start drops by less than 3 kPa (22.5 mmHg) 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 the DTC.

The manifold absolute pressure sensor detects pressure inside the intake manifold as an absolute pressure with a built-in sensor and outputs a voltage. Based on the voltage from the vacuum sensor, the hybrid vehicle control ECU controls the purge VSV and corrects any errors in the pressure sensor due to changes in pressure.

HINT

When DTC P0107 or P0108 is detected, check the manifold absolute pressure by selecting Powertrain / Engine and ECT / Data List / MAP on the Techstream.

The hybrid vehicle control ECU monitors the sensor voltage and uses this value to calculate the manifold absolute pressure. When the sensor output voltage deviates from the normal operating range, the hybrid vehicle control ECU interprets this as a malfunction in the manifold absolute pressure sensor and sets a DTC.

Example

When the sensor output voltage remains less than 0.5 V, or more than 4.5 V for 0.5 seconds, the hybrid vehicle control ECU sets a DTC.

If the malfunction is not repaired successfully, a DTC is set 0.5 seconds after the engine is next started.

1. The intake air temperature sensor, mounted in the mass air flow meter sub-assembly, monitors the intake air temperature. The intake air temperature sensor has a built-in thermistor with a resistance that varies according to the temperature of the intake air. When the intake air 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 hybrid vehicle control ECU as voltage changes (Scheme 121)
2. The intake air temperature sensor is powered by a 5 V supply from the THA terminal of the hybrid vehicle control ECU, via resistor R which is located inside the hybrid vehicle control ECU.
3. Resistor R and the intake air temperature sensor are connected in series. When the resistance value of the intake air temperature sensor changes, according to changes in the intake air temperature, the voltage at terminal THA also varies. Based on this signal, the hybrid vehicle control ECU increases the fuel injection volume when the engine is cold to improve driveability.

Scheme 126

After Warm Engine Stop

The hybrid vehicle control ECU monitors the intake air temperature variation in the period from when the engine was warmed up on the previous trip until the next engine start. If the change in the intake air temperature sensor output is less than the threshold, it is determined that a malfunction has occurred in the intake air temperature sensor. When this is detected, the MIL is illuminated and the DTC is set.

After Cold Engine Start

The monitor runs when the engine is started cold after 5 hours or more have elapsed since the engine was stopped. If the intake air temperature sensor output variation until the engine has warmed up completely is less than the threshold, it is determined that a malfunction has occurred in the intake air temperature sensor. When this is detected in 2 consecutive driving cycles, the MIL is illuminated and the DTC is set.

1. The intake air temperature sensor, mounted in the mass air flow meter sub-assembly, monitors the intake air temperature. The intake air temperature sensor has a built-in thermistor with a resistance that varies according to the temperature of the intake air. When the intake air 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 hybrid vehicle control ECU as voltage changes (Scheme 121)
2. The intake air temperature sensor is powered by a 5 V supply from the THA terminal of the hybrid vehicle control ECU, via resistor R which is located inside the hybrid vehicle control ECU.
3. Resistor R and the intake air temperature sensor are connected in series. When the resistance value of the intake air temperature sensor changes, according to changes in the intake air temperature, the voltage at terminal THA also varies. Based on this signal, the hybrid vehicle control ECU increases the fuel injection volume when the engine is cold to improve driveability. HINT: When either DTC P0112 or P0113 is set, the hybrid vehicle control ECU enters fail-safe mode. During fail-safe mode, the intake air temperature is estimated to be 20°C (68°F) by the hybrid vehicle control ECU. Fail-safe mode continues until a pass condition is detected.

HINT

When any of these DTCs are set, check the intake air temperature by entering the following menus: Powertrain / Engine and ECT / Intake Air.

The hybrid vehicle control ECU 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 hybrid vehicle control ECU interprets this as a malfunction in the intake air temperature sensor and sets a DTC.

Example

If the sensor output voltage is more than 4.91 V for 0.5 seconds or more, the hybrid vehicle control ECU determines that there is an open in the intake air temperature sensor circuit, and sets DTC P0113. Conversely, if the output voltage is less than 0.18 V for 0.5 seconds or more, the hybrid vehicle control ECU 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.

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 hybrid vehicle control ECU are the same as those of the intake air temperature sensor.

HINT

When any of DTCs P0115, P0117 and P0118 are set, the hybrid vehicle control ECU enters fail-safe mode. During fail-safe mode, the engine coolant temperature is estimated to be 80°C (176°F) by the hybrid vehicle control ECU. Fail-safe mode continues until a pass condition is detected.

HINT

When any of these DTCs are set, check the engine coolant temperature by entering the following menus: Powertrain / Engine and ECT / Data List / 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 becomes low, the resistance in the thermistor increases. When the temperature becomes high, the resistance drops. These variations in resistance are reflected in the output voltage from the sensor. The hybrid vehicle control ECU monitors the sensor voltage and uses this value to calculate the engine coolant temperature. When the sensor output voltage deviates from the normal operating range, the hybrid vehicle control ECU interprets this as a fault in the engine coolant temperature sensor circuit and sets a DTC.

Example

If the sensor output voltage is more than 4.91 V for 0.5 seconds or more, the hybrid vehicle control ECU determines that there is an open in the engine coolant temperature sensor circuit, and sets DTC P0118. Conversely, if the voltage output is less than 0.14 V for 0.5 seconds or more, the hybrid vehicle control ECU 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.

Refer to DTC P0115. Refer to DESCRIPTION .

Engine Coolant Temperature Sensor Cold Start Monitor

The monitor runs when the engine is started cold. If the change in engine coolant temperature sensor output until the engine warmed up completely is less than the threshold, it is determined that a malfunction has occurred in the engine coolant temperature sensor. When this is detected in 2 consecutive driving cycles, the MIL is illuminated and the DTC is set.

Engine Coolant Temperature Sensor Soak Monitor

The hybrid vehicle control ECU compares the engine coolant temperature when the warmed engine is stopped and when the engine is started on the next trip after more than 5 hours has elapsed since the engine was stopped. If the change in engine coolant temperature sensor output is less than the threshold, it is determined that a malfunction has occurred in the engine coolant temperature sensor. When this is detected in 2 consecutive driving cycles, the MIL is illuminated and the DTC is set.

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

Scheme 127

HINT

1. Waiting is required to prevent the temperature of the engine from affecting the readings. If the engine has been operated recently, it will not be 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, this does not necessarily indicate a fault.

The hybrid vehicle control ECU monitors the difference between the engine coolant temperature and the intake air temperature when the engine is started cold to detect the engine temperature conditions accurately. The monitor runs when the engine is started cold after 7 hours or more has elapsed since the engine was stopped (power 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 20°C (36°F), the hybrid vehicle control ECU interprets this as a malfunction in the engine coolant temperature sensor circuit and intake air temperature sensor circuit, and sets the DTC.

HINT

1. 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. It uses Hall-effect elements in order to yield accurate signals even in extreme conditions.

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

As the valve closes, the sensor output voltage decreases and as the valve opens, the sensor output voltage increases. The hybrid vehicle control ECU 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 enrichment correction and fuel-cut control.

Scheme 128

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

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

1. A specific voltage difference is expected between the sensor terminals, VTA and VTA2, for each throttle valve opening angle. If the difference between VTA and VTA2 is incorrect, the hybrid vehicle control ECU interprets this as a malfunction in the sensor circuit, and sets a DTC.

1. VTA and VTA2 each have a specific voltage range. If VTA or VTA2 is outside the normal operating range, the hybrid vehicle control ECU interprets this as a malfunction in the sensor circuit, and sets a DTC.

1. VTA and VTA2 should never be close to the same voltage level. If VTA is within 0.02 V of VTA2, the hybrid vehicle control ECU determines that there is a short circuit in the sensor circuit, and sets a DTC.

If the malfunction is not repaired successfully, a DTC is set 10 seconds after the engine is next started.

P0121

For each throttle opening angle, a specific voltage difference is expected between the outputs of VTA and VTA2. If the output voltage difference between the two signals deviates from the normal operating range, the hybrid vehicle control ECU interprets this as a malfunction in the throttle position sensor. The hybrid vehicle control ECU illuminates the MIL and stores the DTC.

This sensor transmits two signals: VTA and VTA2. VTA is used to detect the throttle opening angle and VTA2 is used to detect malfunctions in VTA. The hybrid vehicle control ECU performs several checks to confirm the proper operation of the throttle position sensor and VTA.

If the malfunction is not repaired successfully, the DTC is stored 2 seconds after the engine is next started.

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 hybrid vehicle control ECU 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 through 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 hybrid vehicle control ECU interprets this as a malfunction in the sensor or cooling system and sets the DTC.

Example

The engine coolant temperature is 5°C (41°F) at engine start. After about 1 minute running time, the engine coolant temperature sensor still indicates that the engine is not warm enough to begin closed-loop fuel (air fuel ratio feedback) control. The hybrid vehicle control ECU interprets this as a malfunction in the sensor or cooling system and sets the DTC.

HINT

1. This DTC relates to the thermostat.

This DTC is set when the engine coolant temperature does not reach 75°C (167°F) despite sufficient engine warm-up time having elapsed.

Scheme 129

The hybrid vehicle control ECU estimates the engine coolant temperature based on the starting temperature, engine load, and engine speeds. The hybrid vehicle control ECU then compares the estimated temperature with the actual engine coolant temperature. When the estimated engine coolant temperature reaches 75°C (167°F), the hybrid vehicle control ECU checks the actual engine coolant temperature. If the actual engine coolant temperature is less than 75°C (167°F), the hybrid vehicle control ECU interprets this as a malfunction in the water inlet with thermostat sub-assembly or the engine cooling system and sets the DTC.

HINT

Bank 1 sensor 2 refers to the sensor mounted behind the three way catalytic converter and located far from the engine assembly.

A three way catalytic converter is used in order to convert the carbon monoxide, hydrocarbons, and nitrogen oxide, into less harmful substances. To allow the three way catalytic converter to function effectively, it is necessary to keep the air fuel ratio of the engine near the stoichiometric air fuel ratio. For the purpose of helping the hybrid vehicle control ECU to deliver accurate air fuel ratio control, a heated oxygen sensor is used.

The heated oxygen sensor is located behind the three way catalytic converter, 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 great. The heated oxygen sensor informs the hybrid vehicle control ECU that the post-three way catalytic converter 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 becomes small. The heated oxygen sensor informs the hybrid vehicle control ECU that the post-three way catalytic converter air fuel ratio is rich (high voltage, i.e. more 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 hybrid vehicle control ECU uses the supplementary information from the heated oxygen sensor to determine whether the air fuel ratio after the three way catalytic converter is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the hybrid vehicle control ECU is unable to compensate for deviations in the primary air fuel ratio control.

Scheme 130

Scheme 131

Scheme 132

Scheme 133

1. Active Air Fuel Ratio Control The hybrid vehicle control ECU 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 hybrid vehicle control ECU performs active air fuel ratio control to detect any deterioration in the three-way catalytic converter and heated oxygen sensor malfunctions ( (Scheme 131)the diagram below). Active air fuel ratio control is performed for approximately 15 to 25 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 hybrid vehicle control ECU. If the hybrid vehicle control ECU detects a malfunction, a DTC is set.
2. Abnormal Voltage Output of Heated Oxygen Sensor (DTC P0136) While the hybrid vehicle control ECU 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 decrease to less than 0.21 V or does not increase to mote than 0.59 V during active air fuel ratio control, the hybrid vehicle control ECU determines that the sensor voltage output is abnormal and sets DTC P0136.
3. Open or Short in Heated Oxygen Sensor Circuit (DTCs P0137 or P0138) During active air fuel ratio control, the hybrid vehicle control ECU calculates the oxygen storage capacity* of the three-way catalytic converter by forcibly regulating the air fuel ratio to become rich or lean. If the heated oxygen sensor has an open or short, or the voltage output of the sensor noticeably decreases, the oxygen storage capacity indicates an extraordinarily high value. Even if the hybrid vehicle control ECU 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 hybrid vehicle control ECU interprets this as an abnormally low sensor output voltage and sets DTC P0137. When the target air fuel ratio is lean and the voltage output is 0.59 V or more (rich) during active air fuel ratio control, the hybrid vehicle control ECU determines that the sensor voltage output is abnormally high, and sets DTC P0138. HINT: DTC P0138 is also set if the heated oxygen sensor voltage output is more than 1.2 V for 10 seconds or more. *: The three-way catalytic converter has the capability to store oxygen. The oxygen storage capacity and the emission purification capacity of the three-way catalytic converter are mutually related. The hybrid vehicle control ECU determines whether the catalyst has deteriorated, based on the calculated oxygen storage capacity value. Refer to «MONITOR DESCRIPTION»(ref-398227-S01883854412011051600000).
4. High or Low Impedance of Heated Oxygen Sensor (DTCs 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 hybrid vehicle control ECU. The hybrid vehicle control ECU 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 hybrid vehicle control ECU stores the DTC by calculating the impedance of the sensor when the typical enabling conditions are satisfied (2 driving cycles). DTC P0137 indicates an open or short circuit in the heated oxygen sensor (2 driving cycles). The hybrid vehicle control ECU stores the DTC when the impedance of the sensor exceeds the threshold of 15 kohms.
5. Abnormal Voltage Output of Heated Oxygen Sensor During Fuel-cut (DTC P0139) The sensor output voltage drops to below 0.2 V (extremely lean status) immediately when the vehicle decelerates and fuel-cut is operating. If the voltage does not drop to below 0.2 V for 6 seconds or more, or voltage does not drop from 0.35 V to 0.2 V for 1 second or more, the hybrid vehicle control ECU determines that the sensor response has deteriorated, illuminates the MIL and sets a DTC.

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.

If both the short-term and long-term fuel trims are lean or rich beyond predetermined values, it is interpreted as a malfunction, and the hybrid vehicle control ECU illuminates the MIL and stores a DTC.

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 hybrid vehicle control ECU 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 hybrid vehicle control ECU 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 hybrid vehicle control ECU interprets this as a fault in the fuel system and stores a DTC.

Example

The average fuel trim learned value is +35% or more or -35% or less, the hybrid vehicle control ECU interprets this as a fuel system malfunction.

Scheme 134

When the engine misfires, high concentrations of hydrocarbons (HC) enter the exhaust gas. Extremely high hydrocarbon concentration levels can cause an increase in exhaust emission levels. Extremely high concentrations of hydrocarbons can also cause increases in the three-way catalytic converter temperature, which may cause damage to the three-way catalytic converter. To prevent this increase in emissions and to limit the possibility of thermal damage, the hybrid vehicle control ECU monitors the misfire count. When the temperature of the three-way catalytic converter reaches the point of thermal degradation, the hybrid vehicle control ECU blinks the MIL. To monitor misfires, the hybrid vehicle control ECU uses both the camshaft position sensor and the crankshaft position sensor. The camshaft position sensor is used to identify any misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. If the misfire count exceeds the threshold levels, and could cause emission control system performance deterioration, the hybrid vehicle control ECU illuminates the MIL and sets a DTC.

When DTCs for misfiring cylinders are randomly stored, but DTC P0300 is not stored, it indicates that misfires have been detected in different cylinders at different times. DTC P0300 is only stored when several misfiring cylinders are detected at the same time.

The hybrid vehicle control ECU illuminates the MIL and stores a DTC when either one of the following conditions, which could cause emission control system performance deterioration, is detected (2 trip detection logic).

1. Within the first 1000 crankshaft revolutions after the engine starts, an excessive number of misfires (approximately 20 to 50 misfires per 1000 crankshaft revolutions) occurs once.
2. An excessive number of misfires (approximately 20 to 50 misfires per 1000 crankshaft revolutions) occurs a total of 4 times.

The hybrid vehicle control ECU flashes the MIL and stores a DTC when either one of the following conditions, which could cause damage to the three-way catalytic converter, is detected (2 trip detection logic).

HINT

If a catalyst-damaging misfire occurs, the monitor informs the driver by blinking the MIL (1 trip detection logic).

1. In every 200 crankshaft revolutions at a high engine speed, the threshold misfiring percentage is recorded once.
2. In every 200 crankshaft revolutions at a normal engine speed, the threshold misfiring percentage is recorded 3 times.

The hybrid vehicle control ECU illuminates the MIL and stores a DTC when either one of the following conditions, which could cause emission deterioration, is detected (2 trip detection logic).

A flat type knock control sensor is used. Flat type knock control sensors (non-resonant type) have a structure that can detect vibrations over a wide band of frequencies: between approximately 6 kHz and 15 kHz.

Knock control sensors are fitted onto the engine block to detect engine knocking.

The knock control sensor contains a piezoelectric element which generates a voltage when it becomes deformed.

The voltage is generated when the engine block vibrates due to knocking. Occurrence of engine knocking can be suppressed by delaying the ignition timing.

HINT

When either DTC P0327 or P0328 is set, the hybrid vehicle control ECU enters fail-safe mode. During fail-safe mode, the ignition timing is delayed to its maximum retardation. Fail-safe mode continues until the power switch is turned off.

Reference: Inspection using an oscilloscope

Scheme 135

The correct waveform is as shown.

If the output voltage transmitted by the knock control sensor remains low or high for more than 1 second, the hybrid vehicle control ECU interprets this as a malfunction in the sensor circuit, and sets a DTC.

The monitor for DTCs P0327 and P0328 begins to run when 5 seconds have elapsed since the engine was started.

If the malfunction is not repaired successfully, DTC P0327 or P0328 is set 5 seconds after the engine is next started.

The crankshaft position sensor system consists of a crankshaft position sensor plate and a pickup coil.

The sensor plate has 34 teeth and is installed on the crankshaft. The pickup coil is made of wound copper wire, an iron core and magnet. The sensor plate rotates and, as each tooth passes by the pickup coil, a pulse signal is created. The pickup coil generates 34 signals per engine revolution. Based on these signals, the hybrid vehicle control ECU calculates the crankshaft position and engine speed. Using these calculations, the fuel injection time and ignition timing are controlled.

Scheme 136

1. Reference: Inspection using an oscilloscope. HINT: The correct waveform is as shown in the illustration. G2+ is camshaft position sensor signals, and NE+ is the crankshaft position sensor signal. A failure of the ground for the shielding of the wiring may result in noisy waveforms. Terminal Name CH1: Between G2+ and G2- CH2: Between NE+ and NE- Tester Range 5 V/DIV., 20 ms./DIV. Condition Idling with warm engine

If there is no signal from the crankshaft position sensor despite the engine operating, the hybrid vehicle control ECU 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 camshaft position sensor consists of a magnet and an iron core which is wrapped with copper wire, and is installed onto the cylinder head. When the camshaft rotates, each of 3 teeth on the camshaft passes through the camshaft position sensor. This activates the internal magnet in the sensor, generating a voltage in the copper wire. The camshaft rotation is synchronized with the crankshaft rotation. When the crankshaft turns twice, the voltage is generated 3 times in the camshaft position sensor. The generated voltage in the sensor acts as a signal, allowing the hybrid vehicle control ECU to locate the camshaft position. This signal is then used to control ignition timing, fuel injection timing, and the VVT system.

HINT

DTC P0340 indicates a malfunction relating to the camshaft position sensor circuit (the wire harness between the hybrid vehicle control ECU and camshaft position sensor, and the camshaft position sensor itself).

Reference: Inspection using an oscilloscope

HINT

1. The correct waveform is as shown in the illustration.
2. G2+ is the camshaft position sensor signal, and NE+ is the crankshaft position sensor signal.
3. A failure of the ground for the shielding of the wiring may result in noisy waveforms.

If no signal is transmitted by the camshaft position sensor despite the engine revolving, or the rotation of the camshaft and the crankshaft is not synchronized, the hybrid vehicle control ECU interprets this as a malfunction of the sensor.

If the malfunction is not repaired successfully, the DTC is set 10 seconds after the engine is next started.

HINT

1. These DTCs indicate malfunctions relating to the primary circuit.
2. If DTC P0351 is set, check the No. 1 ignition coil assembly circuit.
3. If DTC P0352 is set, check the No. 2 ignition coil assembly circuit.
4. If DTC P0353 is set, check the No. 3 ignition coil assembly circuit.
5. If DTC P0354 is set, check the No. 4 ignition coil assembly circuit.

A Direct Ignition System (DIS) is used on this vehicle.

The DIS is an ignition system in which each cylinder is ignited by it's own ignition coil assembly and spark plug. The secondary wiring of each ignition coil generates a powerful voltage which is applied directly to each spark plug. The spark passes from the center electrode of the spark plug to the ground electrode.

The hybrid vehicle control ECU determines the ignition timing and transmits the ignition (IGT) signals to each cylinder. Using the IGT signal, the hybrid vehicle control ECU turns the power transistor inside the igniter on and off. The power transistor, in turn, switches on and off the current to the primary coil. When the current to the primary coil is cut off, a powerful voltage is generated in the secondary coil. This voltage is applied to the spark plugs, causing them to spark inside the cylinders. As the hybrid vehicle control ECU cuts the current to the primary coil, the igniter sends back an ignition confirmation (IGF) signal to the hybrid vehicle control ECU, for each cylinder ignition.

Scheme 137

Scheme 138

1. Reference: Inspection using an oscilloscope.
2. While cranking or idling the engine, check the waveform between terminals IGT (1 to 4) and E1, and IGF and E1 of the hybrid vehicle control ECU connector. Terminal Name Between IGT (1 to 4) and E1 Between IGF and E1 Tester Range 2 V/DIV., 20 ms./DIV. Condition Idling

Scheme 139

If the hybrid vehicle control ECU does not receive any IGF signals despite transmitting the IGT signal, it interprets this as a fault in the igniter and sets a DTC.

If the malfunction is not repaired successfully, a DTC is set 1 second after the engine is next started.

The hybrid vehicle control ECU uses sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency.

The first sensor, the air fuel ratio sensor, sends pre-catalyst information to the hybrid vehicle control ECU. The second sensor, the heated oxygen sensor, sends post-catalyst information to the hybrid vehicle control ECU.

In order to detect any deterioration in the three-way catalytic converter, the hybrid vehicle control ECU calculates the oxygen storage capacity of the three-way catalytic converter. This calculation is based on the voltage output of the heated oxygen sensor while performing active air fuel ratio control.

The oxygen storage capacity value is an indication of the oxygen storage capacity of the three-way catalytic converter. When the vehicle is being driven with a warm engine, active air fuel ratio control is performed for approximately 15 to 25 seconds. When it is performed, the hybrid vehicle control ECU deliberately sets the air fuel ratio to lean or rich levels. If the cycle of the waveform see scheme 94 for the heated oxygen sensor is long, the oxygen storage capacity is great. There is a direct correlation between the heated oxygen sensor and the oxygen storage capacity of the three-way catalytic converter.

The hybrid vehicle control ECU uses the oxygen storage capacity value to determine the state of the three-way catalytic converter. If any deterioration has occurred, the hybrid vehicle control ECU illuminates the MIL and sets the DTC.

HINT

1. Bank 1 sensor 1 refers to the sensor closest to the engine assembly.
2. Bank 1 sensor 2 refers to the sensor farthest away from the engine assembly.

Scheme 140

TEXT IN ILLUSTRATION

See also:
• REMOVAL - Step 14
• ON-VEHICLE INSPECTION - Step 1
• ON-VEHICLE INSPECTION - Step 2
• ON-VEHICLE INSPECTION - Step 1
• INSPECTION
• COMPONENTS