Engine Control System [2GR-FE] [Diagnostic Codes] [P0010-P0351]: Overview Toyota Sienna III

DESCRIPTION

The Variable Valve Timing (VVT) system includes the ECM, camshaft timing oil control valve assembly and camshaft timing gear assembly. The ECM 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 camshaft timing gear assembly. Camshaft timing control is performed according to engine operating conditions such as intake air volume, throttle valve position and engine coolant temperature. The ECM controls the camshaft timing oil control valve assembly, based on the signals transmitted from several sensors. The camshaft timing gear assembly regulates the intake camshaft angle using oil pressure through the camshaft timing oil control valve assembly. As a result, the relative positions of the camshaft and crankshaft are optimized, the engine torque and fuel economy improve, and the exhaust emissions decrease under overall driving conditions. The ECM detects the actual intake valve timing using signals from the VVT sensor and crankshaft position sensor, and performs feedback control. This is how the target intake valve timing is verified by the ECM.

Scheme 613

MONITOR DESCRIPTION

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

Refer to DTC P0010. Refer to DESCRIPTION.

1. 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 side) and the camshaft timing gear assembly.
2. The ECM sends a target duty-cycle control signal to the camshaft timing oil control valve assembly (for intake side). This control signal regulates the oil pressure supplied to the camshaft timing gear assembly. The camshaft timing gear assembly can advance or retard the intake camshaft.
3. 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 the camshaft timing gear assembly 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 above condition is met, the camshaft timing oil control valve assembly is forcibly activated 10 seconds (Condition "B").
3. DTCs P0011 and P0021 (advanced camshaft timing) are subject to 1 trip detection logic.
4. DTCs P0012 and P0022 (retarded camshaft timing) are subject to 2 trip detection logic.
5. These DTCs indicate that the camshaft timing gear assembly cannot operate properly due to camshaft timing oil control valve assembly (for intake side) malfunctions or the presence of foreign objects in the camshaft timing oil control valve assembly (for intake side).

The Variable Valve Timing (VVT) system includes the ECM, camshaft timing oil control valve assembly (for exhaust side) and camshaft timing exhaust gear assembly. The ECM sends a target duty-cycle control signal to the camshaft timing oil control valve assembly (for exhaust side). This control signal regulates the oil pressure supplied to the camshaft timing exhaust gear assembly. Camshaft timing control is performed according to engine operating conditions such as the intake air volume, throttle valve position and engine coolant temperature. The ECM controls the camshaft timing oil control valve assembly (for exhaust side), based on the signals transmitted by several sensors. The camshaft timing exhaust gear assembly regulates the exhaust camshaft angle using oil pressure through the camshaft timing oil control valve assembly (for exhaust side). As a result, the relative positions of the camshaft and crankshaft are optimized, the engine torque and fuel economy improve, and the exhaust emissions decrease under overall driving conditions. The ECM detects the actual exhaust valve timing using signals from the VVT sensor and crankshaft position sensor, and performs feedback control. This is how the target intake valve timing is verified by the ECM.

Scheme 614

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

Refer to DTC P0013. Refer to DESCRIPTION.

1. 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, camshaft timing oil control valve assembly (for exhaust side) and camshaft timing exhaust gear assembly.
2. The ECM 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 camshaft timing exhaust gear assembly (for exhaust side). The camshaft timing exhaust gear assembly can advance or retard the exhaust camshaft.
3. If the difference between the target and actual exhaust valve timing is large, and changes in actual exhaust valve timing are small, the ECM interprets this as the camshaft timing exhaust gear assembly 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 above condition is met, the camshaft timing oil control valve assembly is forcibly activated 10 seconds (Condition "B").
3. DTCs P0014 and P0024 (advanced camshaft timing) are subject to 2 trip detection logic.
4. DTCs P0015 and P0025 (retarded camshaft timing) are subject to 1 trip detection logic.
5. These DTCs indicate that the camshaft timing exhaust gear assembly cannot operate properly due to camshaft timing oil control valve assembly (for exhaust side) malfunctions or the presence of foreign objects in the camshaft timing oil control valve assembly (for exhaust side).

Refer to DTC P0010. Refer to DESCRIPTION.

The ECM optimizes the valve timing by 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 side) and the camshaft timing gear assembly.

The ECM sends a target duty-cycle control signal to the camshaft timing oil control valve assembly (for intake side). This control signal regulates the oil pressure applied to the camshaft timing gear assembly. The camshaft timing gear assembly 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 camshaft timing oil control valve assembly (for intake side) to retard the cam. The ECM stores this value as the VVT learning value. When the difference between the target and actual intake valve timing is 5°CA (crankshaft angle) or less, the ECM stores it.

If the VVT learning value matches the following conditions, the ECM determines the existence of a malfunction in the VVT system, and stores the DTC.

1. The VVT learning value: Less than 18.5°CA, or more than 43.5°CA.
2. The 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.

Refer to DTC P0013. Refer to DESCRIPTION.

The ECM checks valve timing (VVT learning value) on the exhaust side while the engine is running at a low speed, in order to monitor the gap between the current and target valve timing on the exhaust side. The VVT learning value is calculated from the positions of the camshaft and crankshaft. The camshaft will come to the most retarded position when the engine is running at a low speed. If the camshaft position is normal, the VVT learning value should be within the specified range. If the VVT learning value is not within the specified range, the ECM determines that this is a malfunction.

HINT

1. Although the DTC titles include oxygen sensor, these DTCs relate to the air fuel ratio sensor.
2. Sensor 1 refers to the sensor mounted in front of the three way catalytic converter and located near the engine assembly.

The air fuel ratio sensor generates voltage* that corresponds to the actual air fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air fuel ratio. The ECM determines the deviation from the stoichiometric air fuel ratio level, and regulates the fuel injection time. If the air fuel ratio sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.

The air fuel ratio sensor is the planar type and is integrated with a heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, and therefore the sensor activation is accelerated.

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 three way catalytic converter is used. For the most efficient use of the three way catalytic converter, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.

*: Value changes inside the ECM. Since the air fuel ratio sensor is the current output element, the current is converted to a voltage inside the ECM. Any measurements taken at the air fuel ratio sensor or ECM connectors will show a constant voltage.

Scheme 615

HINT

Scheme 616

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. The ECM provides 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.

1. 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.
2. 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.
3. 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.
4. 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 will be inaccurate, as a result, the ECM will be unable to regulate air fuel ratio properly.
5. 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.

A three-way catalytic converter is used in order to convert the carbon monoxides (CO), hydrocarbon (HC), and nitrogen oxide (NOx) 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 ECM 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 becomes rich. The heated oxygen sensor informs the ECM 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 lean. The heated oxygen sensor informs the ECM 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 ECM 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 ECM is unable to compensate for deviations in the primary air fuel ratio control.

Scheme 617

HINT

Scheme 618

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 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.
3. The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The heated oxygen sensor heater circuit uses a relay on the +B side of the circuit.

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, P0038, P0057, P0058, P102D and P105D)

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 and stores a DTC.

Heated Oxygen Sensor Heater Performance (P0141 and P0161)

1. After the accumulated heater on time exceeds 100 seconds, the ECM calculates the heater resistance using the battery voltage and the current applied to the heater. If the resistance is above the threshold value, the ECM will determine that there is a malfunction in the heated oxygen sensor heater and store DTCs P0141 and P0161.

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 ECM 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 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 these components of the mass air flow meter. 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 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 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 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 the 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 ECM heats it to a given 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 these components in the mass air flow meter. The voltage level is proportional to the air flow 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 619

HINT

When any of these DTCs are stored, check the air flow rate by entering the following menus on the Techstream: Powertrain / Engine / Data List / MAF.

If there is a defect in the mass air flow 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 mass air flow meter and stores 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 ECM stores a DTC.

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

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 that the intake air temperature sensor value is stuck by monitoring the sensor after the ignition switch is turned off or after the engine is started.

1. The intake air temperature sensor, in the mass air flow meter, 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 ECM as voltage changes (Scheme 613)
2. The intake air temperature sensor is powered by a 5 V supply from the THA terminal of the ECM, via resistor R which is located inside the ECM.
3. Resistor R and the intake air temperature sensor are connected in series. When the resistance value of the intake air temperature sensor changes, the voltage at terminal THA varies accordingly. Based on this signal, the ECM increases the fuel injection volume when the engine is cold to improve driveability. HINT: When any of DTCs P0112 and P0113 are stored, the ECM enters fail-safe mode. During fail-safe mode, the intake air temperature is estimated to be 20°C (68°F) by the ECM. Fail-safe mode continues until a pass condition is detected.

HINT

When any of these DTCs are output, check the intake air temperature by entering the following menus on the Techstream: Powertrain / Engine / Data List / Intake Air.

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 and stores a DTC.

Example

If the sensor output voltage is more 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.

If the malfunction is not repaired successfully, a DTC is stored 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 ECM are similar to those of the intake air temperature sensor.

HINT

When any of DTCs 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 by entering the following menus on the Techstream: Powertrain / Engine / Data List / Coolant Temp.

1. 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 ECM 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 ECM interprets this as a malfunction in the engine coolant temperature sensor and stores a DTC. Example: If the sensor output voltage is more 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. If the malfunction is not repaired successfully, a DTC is stored 0.5 seconds after the engine is next started.

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 a 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 a DTC is stored.

Engine coolant temperature sensor high side stuck monitor (only for Mexico models)

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

Examples

1. Upon starting the engine, the engine coolant temperature is between 35°C and 60°C (95°F and 140°F). If after driving for 250 seconds, the engine coolant temperature remains within 3°C (5.4°F) of the starting temperature, the DTC is stored (2 trip detection logic).
2. Upon starting the engine, the engine coolant temperature is over 60 °C (140°F). If after driving at varying speeds (accelerating and decelerating) for a specified period of time, the engine coolant temperature remains within 1°C (1.8°F) of the starting temperature, the DTC is stored (6 trip detection logic).

The engine has 2 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 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 620

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 ECM 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 started cold after 7 hours or more has elapsed since the engine was stopped (ignition switch turned to 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 ECM interprets this as a malfunction in the engine coolant temperature sensor circuit and intake air temperature sensor circuit, and stores the DTC.

HINT

1. These DTCs relate to the throttle position sensor.

The throttle position sensor is mounted on the throttle with motor 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, each of which transmits a signal, VTA1 and VTA2. 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 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 621

HINT

1. When any of these DTCs are output, check the throttle valve opening angle using the Techstream. Enter the following menus: Powertrain / Engine / Data List / 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

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

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.

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.

1. 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.

1. 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 circuit in the sensor circuit, and stores a DTC.

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

P0121

This sensor transmits 2 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 2 signals deviates from the normal operating range, the ECM interprets this as a malfunction in the throttle position sensor. The ECM illuminates the MIL and stores the DTC.

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 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 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 ECM interprets this as a malfunction in the sensor or cooling system and stores the DTC.

Example

The engine coolant temperature is 0°C (32°F) at engine start. After approximately 70 seconds of 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 ECM interprets this as a malfunction in the sensor or cooling system and stores the DTC.

HINT

This DTC relates to the thermostat.

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

Scheme 622

The ECM estimates the engine coolant temperature based on the starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual engine coolant temperature. When the estimated engine coolant temperature reaches 75°C (167°F), the ECM checks the actual engine coolant temperature. If the actual engine coolant temperature is less than 75°C (167°F), the ECM interprets this as a malfunction in the thermostat or the engine cooling system and stores the 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.

FOR MEXICO MODELS

Scheme 623

Scheme 624

Scheme 625

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 (DTCs P0136 and P0156) 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 0.59 V or higher during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormal and stores DTC P0136 or P0156.
3. Open in Heated Oxygen Sensor Circuit (DTCs P0137 and P0157) 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 or P0157. 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 «DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1); DTC P0430: Catalyst System Efficiency Below Threshold (Bank 2)»(ref-494146-S00233809792012081000000).
4. High or Low Impedance of Heated Oxygen Sensor (DTCs P0136 and P0156 or P0137 and P0157) 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 or P0156 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 driving cycles). DTC P0137 or P0157 indicates an open or short circuit in the heated oxygen sensor (2 driving cycles). 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 (DTCs P0138 and P0158) The ECM continuously monitors the heated oxygen sensor output voltage while the engine is running. DTC P0138 or P0158 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 (DTCs P0139 and P0159) 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 when accumulated intake air mass is more than 11.3 g, or voltage does not drop from 0.35 V to 0.2 V for 1 second or more, the ECM determines that the sensor response has deteriorated, illuminates the MIL and stores a DTC.

HINT

1. Refer to DTC P2195. Refer to «DESCRIPTION»(ref-494144-S13605009422012081000000).
2. Sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.

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

After the engine is warm, the ECM carries out air fuel ratio feedback control, and maintains the air fuel ratio at the theoretical level. In addition, after all the preconditions have been met, active air fuel ratio control is carried out for approx. 10 seconds, and during active air fuel ratio control, the ECM measures the response of the air fuel ratio sensor by increasing or decreasing a specific injection volume based on the theoretical 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 response ability is reduced, DTC P014C, P014D, P014E and P014F are output.

If the time it takes the air fuel ratio sensor output to change is delayed, DTC P015A, P015B, P015C and P015D are output.

Scheme 626

The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim consists of both the short-term and the 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 it is 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 or P0174 is stored, the actual air fuel ratio is on the lean side. When DTC P0172 or P0175 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 or P0174 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 more 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 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 stores a DTC.

Example

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

Scheme 627

As shown in the illustration, when the engine is cranked, current flows from the terminal ST1 of the ignition switch into the ECM and the ST (starter) relay coil and also current flows to terminal STA of the ECM (STA signal).

When the STA signal and NE signal are input to the ECM, Tr1 (power transistor 1) is turned ON, current flows to the coil of the circuit opening relay, the relay switches on, power is supplied to the fuel pump, and the fuel pump operates.

While the NE signal is generated (engine running), the ECM keeps the Tr1 ON (C/OPN relay ON) and the fuel pump also keeps operating.

The fuel pump speed is controlled at two levels (high speed or low speed) by engine condition (starting, light load, heavy load). When the engine starts (STA ON), Tr2 (power transistor 2) in the ECM is OFF, so the fuel pump relay closes and positive battery voltage is applied directly to the fuel pump. The fuel pump operated at high speed.

During idling or under light loads, Tr2 goes ON, and then power is supplied to the fuel pump via the fuel pump resistor. The fuel pump operates at low speed.

Scheme 628

Scheme 629

The ECM 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).

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

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

1. At a high engine speed, a catalyst damage misfire, which is monitored every 200 crankshaft revolutions, occurs once.
2. At a normal engine speed, a catalyst damage misfire, which is monitored every 200 crankshaft revolutions, occurs 3 times.

HINT

If a catalyst damage misfire occurs, the ECM informs the driver by flashing the MIL.

Misfire Monitor for Mexico Models

The ECM 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).

1. Within the first 1000 crankshaft revolutions of the engine starting, an excessive misfiring rate (approximately 332 misfires per 1000 crankshaft revolutions) occurs once.
2. An excessive misfiring rate (approximately 166 misfires per 1000 crankshaft revolutions) occurs a total of 4 times.

The ECM flashes the MIL and stores a DTC when the following condition, which could cause the three-way catalytic converter damage, is detected (2 trip detection logic).

1. A catalyst damage misfire, which is monitored every 200 crankshaft revolutions, occurs 3 times.

A flat type knock sensor (non-resonant type) has a structure that can detect vibration between approximately 5 kHz and 15 kHz.

knock sensors are fitted onto the engine block to detect engine knocking.

The knock 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. Any occurrence of engine knocking can be suppressed by delaying the ignition timing.

HINT

When any of DTCs P0327, P0328, P0332 and P0333 are stored, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is delayed to its maximum retardation. Fail-safe mode continues until the ignition switch is turned off.

Reference: Inspection using an oscilloscope

Scheme 630

The correct waveform is as shown in the illustration.

The knock sensor, located on the cylinder block, detects spark knock. When spark knock occurs, the piezoelectric element of the sensor vibrates. When the ECM detects a 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, or if the knock sensor output voltage is outside the normal range, the ECM interprets this as a fault in the knock sensor and stores a DTC.

The crankshaft position sensor system consists of a crank angle sensor plate and a pickup coil. The sensor plate has 34 teeth and is installed on the crankshaft. The pickup coil is made of an iron core and a magnet.

The sensor plate rotates and, as each tooth passes through the pickup coil, a pulse signal is created. The pickup coil generates 34 signals per engine rotation. Based on these signals, the ECM calculates the crankshaft position and engine speed. Using these calculations, the fuel injection timing and ignition timing are controlled.

Scheme 631

1. Reference: Inspection using an oscilloscope HINT: The correct waveform is as shown. VV1+ and VV2+ stand for the VVT sensor signal, and NE+ stands for the crankshaft position sensor signal. Item Content ECM Terminal Names Between VV1+ and VV1-, VV2+ and VV2- 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 revolving, the ECM interprets this as a malfunction of the sensor.

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

The VVT sensor (for intake side) (VV1, VV2 signal) consists of a magnet and MRE (Magnet Resistive Element).

The camshaft timing gear assembly has a sensor plate with 3 teeth on its outer circumference. When the gear rotates, changes occur in the air gaps between the sensor plate and MRE, which affects the magnetic field. As a result, the resistance of the MRE material fluctuates. The VVT sensor converts the gear rotation data to pulse signals, uses the pulse signals to determine the camshaft angle, and sends it to the ECM.

The crank angle sensor plate has 34 teeth. The pickup coil generates 34 signals for each engine rotation. Based on combination of the VVT signals and NE signal, the ECM detects the crankshaft angle. Then the ECM uses this data to control fuel injection time and injection timing. Also, based on the NE signal, the ECM detects the engine speed.

1. Reference: Inspection using an oscilloscope HINT: The correct waveform is as shown. VV1+ and VV2+ stand for the VVT sensor (for intake side) signal, and NE+ stands for the crankshaft position sensor signal. Item Content ECM Terminal Names Between VV1+ and VV1-, VV2+ and VV2- Between NE+ and NE- Tester Range 5 V/DIV. 20 ms./DIV. Condition Idling with warm engine

If no signal is transmitted by the VVT sensor (for intake side) despite the engine revolving, or the rotations of the camshaft and the crankshaft are not synchronized, the ECM interprets this as a malfunction of the sensor.

HINT

1. These DTCs indicate malfunctions relating to the primary circuit.
2. If DTC P0351 is stored, check the No. 1 ignition coil assembly circuit.
3. If DTC P0352 is stored, check the No. 2 ignition coil assembly circuit.
4. If DTC P0353 is stored, check the No. 3 ignition coil assembly circuit.
5. If DTC P0354 is stored, check the No. 4 ignition coil assembly circuit.
6. If DTC P0355 is stored, check the No. 5 ignition coil assembly circuit.
7. If DTC P0356 is stored, check the No. 6 ignition coil assembly circuit.

A direct ignition system is used on this vehicle.

The direct ignition system is a 1-cylinder ignition system in which each cylinder is ignited by one ignition coil assembly and a spark plug is connected to the end of each secondary wiring. A powerful voltage, generated in the secondary wiring, is applied directly to each spark plug. Spark of the spark plugs passes from the center electrode to the ground electrodes.

The ECM determines the ignition timing and transmits the ignition signals (IGT) to each cylinder. Using the IGT signal, the ECM 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 ECM cuts the current to the primary coil, the igniter sends back an ignition confirmation signal (IGF) to the ECM, for each cylinder ignition.

Scheme 632

Scheme 633

1. Reference: Inspection using an oscilloscope
2. While cranking or idling the engine, check the waveform between terminals IGT (1 to 6) and E1, and IGF1 and E1 of the ECM connectors. HINT: The wavelength becomes shorter as the engine speed increases. Item Content ECM Terminal Names Between IGT (1 to 6) and E1 Between IGF1 and E1 Tester Range 2 V/DIV., 20 ms./DIV. Condition Idling with warm engine

Scheme 634

If the ECM does not receive any IGF signals despite the IGT signal being transmitted, it interprets this as a fault in the igniter and stores a DTC.

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

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