Engine Control System (Diagnostic Codes (P0365 - U0101) & Circuit Tests): Overview Lexus GS III facelift

DESCRIPTION

The exhaust camshaft's Variable Valve Timing (VVT) sensor consists of a magnet and MRE (Magnetic Resistance Element).

The exhaust camshaft has a sensor plate with 3 teeth on its outer circumference.

When the exhaust camshaft rotates, changes occur in the air gaps between the 3 teeth and MRE, which affects the magnet. As a result, the resistance of the MRE material fluctuates. The VVT sensor converts the exhaust camshaft rotation data to pulse signals, uses the pulse signals to determine the camshaft angle, and sends it to the ECM.

Scheme 37

1. Reference: Inspection using an oscilloscope HINT: The correct waveform is as shown. EV1+ and EV2+ stand for the VVT sensor signal, and NE+ stands for the CKP sensor signal. Item Content Terminal NE+ - NE- EV1+ - EV1- EV2+ - EV2- Equipment Setting 5 V/DIV. 20 msec./DIV. Condition Cranking or idling

MONITOR DESCRIPTION

If no signal is transmitted by the VVT sensor 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.

The ECM 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 (A/F) sensor, sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor, sends post-catalyst information to the ECM.

In order to detect any deterioration in the TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the HO2 sensor while performing active air fuel ratio control, rather than the conventional detecting method, which uses the locus ratio.

The OSC value is an indication of the oxygen storage capacity of the TWC. When the vehicle is being driven with a warm engine, active air fuel ratio control is performed for approximately 15 to 20 seconds. When it is performed, the ECM deliberately sets the air fuel ratio to lean or rich levels. If a rich-lean cycle of the HO2 sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the HO2 sensor and the TWC.

The ECM uses the OSC value to determine the state of the TWC. If any deterioration has occurred, it illuminates the MIL and sets a DTC.

HINT

1. Bank 1 refers to the bank that includes No. 1 cylinder.
2. Bank 2 refers to the bank that does not include No. 1 cylinder.
3. Sensor 1 refers to the sensor closest to the engine assembly.
4. Sensor 2 refers to the sensor farthest away from the engine assembly.

The description can be found in the EVAP (Evaporative Emission) System. Refer to DESCRIPTION.

5 hours* after the engine switch is turned off, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.

HINT

*: If the engine coolant temperature is not below 35°C (95°F) 5 hours after the engine switch is turned off, the monitor check starts 2 hours later. If it is still not below 35°C (95°F) 7 hours after the engine switch is turned off, the monitor check starts 2.5 hours later.

*: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

Scheme 38

The leak detection pump creates negative pressure through the reference orifice. When the system is normal, the EVAP pressure is between 724 to 752 mmHg* and saturated within a minute. If not, the ECM interprets this as a malfunction. The ECM will illuminate the MIL and set a DTC if this malfunction is detected in consecutive drive cycles.

*: Typical value.

Scheme 39

The description can be found in the EVAP (Evaporative Emission) System. Refer to DESCRIPTION.

The two monitors, Key-Off and Purge Flow, are used to detect malfunctions relating to DTC P0441. The Key-Off monitor is initiated by the ECM internal timer, known as the soak timer, 5 hours* after the engine switch is turned off. The purge flow monitor runs while the engine is running.

Scheme 40

Scheme 41

Scheme 42

1. KEY-OFF MONITOR 5 hours* after the engine switch is turned off, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure. HINT: *: If the engine coolant temperature is not below 35°C (95°F) 5 hours after the engine switch is turned off, the monitor check starts 2 hours later. If it is still not below 35°C (95°F) 7 hours after the engine switch is turned off, the monitor check starts 2.5 hours later. Sequence Operation Description Duration - ECM activation Activated by soak timer 5, 7 or 9.5 hours after engine switch turned off. - A Atmospheric pressure measurement Vent valve turned OFF (vent) and EVAP system pressure measured by ECM in order to register atmospheric pressure. If pressure in EVAP system not between 76 kPa and 110 kPa (570 mmHg and 825 mmHg), ECM cancels EVAP system monitor. 10 seconds B First reference pressure measurement In order to determine reference pressure, leak detection pump creates negative pressure (vacuum) through reference orifice and then ECM checks if leak detection pump and vent valve operate normally. 60 seconds C EVAP system pressure measurement Vent valve turned ON (closed) to shut EVAP system. Negative pressure (vacuum) created in EVAP system, and EVAP system pressure then measured. Write down measured value as it will be used in leak check. If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor. 15 minutes * D Purge VSV monitor Purge VSV opened and then EVAP system pressure measured by ECM. Large increase indicates normality. 10 seconds E Second reference pressure measurement After second reference pressure measurement, leak check performed by comparing first and second reference pressure. If stabilized system pressure higher than second reference pressure, ECM determines that EVAP system leaking. 60 seconds - Final check Atmospheric pressure measured and then monitoring result recorded by ECM. - *: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize. Purge VSV stuck open In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The EVAP system pressure is then measured by the ECM using the canister pressure sensor. If the stabilized system pressure is higher than [second reference pressure x 0.2], the ECM interprets this as the purge VSV (Vacuum Switching Valve) being stuck open. The ECM illuminates the MIL and sets the DTC (2 trip detection logic). Purge VSV stuck closed In operation D, the canister pressure sensor measures the EVAP system pressure. The pressure measurement for the purge VSV monitor is begun when the purge VSV is turned ON (open) after the EVAP leak check. When the measured pressure indicates an increase of 0.3 kPa-g (2.25 mmHg-g) or more, the purge VSV is functioning normally. If the pressure does not increase, the ECM interprets this as the purge VSV being stuck closed. The ECM illuminates the MIL and sets the DTC (2 trip detection logic).
2. PURGE FLOW MONITOR The purge flow monitor consists of the two step monitors. The 1st monitor is conducted every time and the 2nd monitor is activated if necessary.

1. The 1st monitor While the engine is running and the purge VSV is ON (open), the ECM monitors the purge flow by measuring the EVAP pressure change. If negative pressure is not created, the ECM begins the 2nd monitor.
2. The 2nd monitor The vent valve is turned ON (closed) and the EVAP pressure is then measured. If the variation in the pressure is less than 0.5 kPa (3.75 mmHg), the ECM interprets this as the purge VSV being stuck closed, illuminates the MIL and sets DTC P0441 (2 trip detection logic).

Atmospheric pressure check

In order to ensure reliable malfunction detection, the variation between the atmospheric pressures, before and after conduction of the purge flow monitor, is measured by the ECM.

The circuit description can be found in the Evaporative Emission (EVAP) system. Refer to DESCRIPTION.

Scheme 43

1. DTC P0450: Canister pressure sensor voltage abnormal fluctuation If the canister pressure sensor voltage output rapidly fluctuates between less than 0.45 V and more than 4.9 V, the ECM interprets this as an open or short circuit malfunction in the canister pressure sensor or its circuit, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC (1 trip detection logic).
2. DTC P0451: Canister pressure sensor noisy or stuck If the canister pressure sensor voltage output fluctuates rapidly for 10 seconds, the ECM stops the EVAP system monitor. The ECM interprets this as noise from the canister pressure sensor, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC. Alternatively, if the sensor voltage output does not change for 10 seconds, the ECM interprets this as the sensor being stuck, and stops the monitor. The ECM then illuminates the MIL and sets the DTC. (Both of the malfunctions are detected by 2 trip detection logic).
3. DTC P0452: Canister pressure sensor voltage low If the canister pressure sensor voltage output is below 0.45 V, the ECM interprets this as an open or short circuit malfunction in the canister pressure sensor or its circuit, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC (1 trip detection logic).
4. DTC P0453: Canister pressure sensor voltage high If the canister pressure sensor voltage output is 4.9 V or more, the ECM interprets this as an open or short circuit malfunction in the canister pressure sensor or its circuit, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC (1 trip detection logic).

The description can be found in the EVAP (Evaporative Emission) System. Refer to DESCRIPTION.

5 hours* after the engine switch is turned off, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.

HINT

*: If the engine coolant temperature is not below 35°C (95°F) 5 hours after the engine switch is turned off, the monitor check starts 2 hours later. If it is still not below 35°C (95°F) 7 hours after the engine switch is turned off, the monitor check starts 2.5 hours later.

*: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

Scheme 44

1. (a) P0455: EVAP gross leak In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP system and the EVAP system pressure is measured. If the stabilized system pressure is higher than [second reference pressure x 0.2] (near atmospheric pressure), the ECM determines that the EVAP system has a large leakage, illuminates the MIL and sets the DTC (2 trip detection logic).
2. (b) P0456: EVAP very small leak In operation C, the leak detection pump creates negative pressure (vacuum) in the EVAP system and the EVAP system pressure is measured. If the stabilized system pressure is higher than the second reference pressure, the ECM determines that the EVAP system has a small leakage, illuminates the MIL and sets the DTC (2 trip detection logic).

The stop light switch is a duplex system that transmits 2 signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch and sets the DTC.

HINT

The normal signal conditions are as shown in the table below.

1. [OFF] denotes ground potential.
2. [ON] denotes battery potential (+B).
3. On the Techstream, both the Data List items Stop Light Switch and ST1 are ON when the brake pedal is depressed because the ST1 indication characteristic is opposite to the Stop Light Switch indication.

Scheme 45

The idle speed is controlled by the Electronic Throttle Control System (ETCS). The ETCS is comprised of: 1) one valve type throttle body; 2) the throttle actuator, which operates the throttle valve; 3) the throttle position sensor, which detects the opening angle of the throttle valve; 4) the accelerator pedal position sensor, which detects the accelerator pedal position; and 5) the ECM, which controls the ETCS. Based on the target idle speed, the ECM controls the throttle actuator to provide the proper throttle valve opening angle.

The ECM monitors the idling speed and idling air flow volume to conduct Idle Speed Control (ISC). The ECM determines that the ISC system is malfunctioning if the following conditions are met

Scheme 46

1. The learned idling air flow volume remains at the maximum or minimum volume 5 seconds or more during a drive cycle.
2. After driving at a vehicle speed of 6.25 mph (10 km/h) or more, the actual engine idling speed varies from the target idling speed by more than -100 rpm or 150 rpm or more when the A/C and NSW are off, or more than -100 rpm or 200 rpm or more when the A/C or NSW are on, 5 times or more during a driving cycle, the ECM illuminates the MIL and sets the DTC.

This monitor will run when the engine is started at -10 to 50°C (14 to 122°F) of the engine coolant temperature. The DTC will be set after the engine has been idling for 13 seconds (2 trip detection logic).

The DTC is designed to monitor the idle air control at cold start. When the engine is started at a temperature lower than 50°C (122°F) of the engine coolant temperature, the ECM measures the accumulated mass air flow when the engine is idling. If it does not reach the criteria within 10 seconds, the ECM interprets this as a malfunction. The MIL is illuminated and a DTC is set when the malfunction is detected in consecutive driving cycles (2 trip detection logic).

The ETCS (Electrical Throttle Control System) controls the idle speed. The ETCS operates the throttle actuator to open and close the throttle valve, and adjusts the intake air amount to achieve the target idle speed.

Note. When the negative battery terminal is disconnected during inspection or repairs, the ISC (Idle Speed Control) learned values are cleared. ISC learning is performed when the engine has been warmed up and idled for 5 minutes because this DTC cannot be set after the ISC learned values are cleared.

Scheme 47

This monitor will run when the engine is started at -10 to 50°C (14 to 122°F) of the engine coolant temperature. The DTC will be set after the engine has been idling for 13 seconds (2 trip detection logic).

The DTC is designed to monitor the idle air control at cold start. When the engine is started at a temperature lower than 50°C (122°F) of the engine coolant temperature, the ECM measures the accumulated mass air flow when the engine is idling. If it does not reach the criteria within 10 seconds, the ECM interprets this as a malfunction. The MIL is illuminated and a DTC is set when the malfunction is detected in consecutive driving cycles (2 trip detection logic).

The ETCS (Electrical Throttle Control System) controls the idle speed. The ETCS operates the throttle actuator to open and close the throttle valve, and adjusts the intake air amount to achieve the target idle speed.

Note. When the negative battery terminal is disconnected during inspection or repairs, the ISC (Idle Speed Control) learned values are cleared. ISC learning is performed when the engine has been warmed up and idled for 5 minutes because this DTC cannot be set after the ISC learned values are cleared.

Scheme 48

The battery supplies electricity to the ECM even when the engine switch is in the off position. This power allows the ECM to store data such as DTC history, freeze frame data and fuel trim values. If the battery voltage falls below a minimum level, the stored ECM data is cleared and the ECM determines that there is a malfunction in the power supply circuit. When the engine is next started, the ECM will illuminate the MIL and sets the DTC.

HINT

If DTC P0560 is set, the ECM does not store other DTCs.

The ECM continuously monitors its internal memory status. This self-check ensures that the ECM is functioning properly. It is diagnosed by internal "mirroring" of the main CPU and sub CPU to detect the Random Access Memory (RAM) errors. If outputs from these CPUs are different and deviate from the standards, the ECM will illuminate the MIL and set the DTC immediately.

The ECM continuously monitors its internal processors (CPUs) and heated oxygen sensor (HO2S) transistors. This self-check ensures that the ECM is functioning properly. These are diagnosed by internal "mirroring" of the main and sub CPUs to detect the processors error. If outputs from the processors deviate from the standards, the ECM will illuminate the MIL and set the DTC immediately.

Note. First check for an exhaust gas leak around the HO2S if P0606 is present. An exhaust gas leak generates noise in the HO2S output. The ECM may interpret this as an HO2S transistor malfunction and set P0606.

The ECM continuously monitors its main and sub CPUs. This self-check ensures that the ECM is functioning properly. If outputs from the CPUs are different and deviate from the standards, the ECM will illuminate the MIL and set the DTC immediately.

The ECM also monitors the cruise control cancel circuit. If this circuit malfunctions, the ECM will set the DTC immediately (MIL is not illuminated).

While the engine is being cranked, the positive battery voltage is applied to terminal STA of the ECM.

If the ECM detects the Starter Control (STA) signal while the vehicle is being driven, it determines that there is a malfunction in the STA circuit. The ECM then illuminates the MIL and sets the DTC.

This monitor runs when the vehicle is driven at 12.4 mph (20 km/h) for over 20 seconds.

DTC P0630 is set when the Vehicle Identification Number (VIN) is not stored in the Engine Control Module (ECM) or the input VIN is not accurate. Input the VIN with the Techstream.

The ECM monitors the output voltage to the throttle actuator. This self-check ensures that the ECM is functioning properly. The output voltage is usually 0 V when the engine switch is turned off. If the output voltage is higher than 7 V when the engine switch is turned off, the ECM will illuminate the MIL and set the DTC when the engine switch is turned on (IG).

The purpose of this circuit is to prevent the engine from stalling, while driving in lock-up condition, when brakes are suddenly applied.

When the brake pedal is depressed, this switch sends a signal to the ECM. Then the ECM cancels the operation of the lock-up clutch while braking is in progress.

This DTC indicates that the stop light switch remains on. When the stop light switch remains on during "stop and go" driving, the ECM interprets this as a fault in the stop light switch, the MIL comes on and the ECM stores the DTC. The vehicle must stop (less than 1.86 mph [3 km/h]) and go (18.65 mph [30 km/h] or more) 5 times during 2 driving cycles, in order to detect a malfunction.

The high pressure side fuel pump is attached to the insulator, which is attached to the cylinder head cover. The pump activates according to the position of the cam on the exhaust side camshaft (right bank).

The fuel pump for high pressure increases the pressure of the fuel supplied from the fuel pump in the fuel tank to 4 to 13 MPa (40.8 to 132.6 kgf/cm 2 , 580 to 1885 psi) according to the operating condition, and it feeds the fuel to the fuel delivery pipe.

The D-4S system has two injection systems. One is the in-cylinder direct injection system that directly injects pressurized fuel into the combustion chamber. The other is the intake port injection system. The ECM determines the percentage of in-cylinder direct injection to the intake port injection systems in accordance with the engine speed and load.

The ECM monitors the injection control of the port injector. If a malfunction is detected in the port injector circuit, the ECM cancels the injection control for the corresponding cylinder and turns on the MIL.

The throttle actuator is operated by the ECM and opens and closes the throttle valve using gears.

The opening angle of the throttle valve is detected by the Throttle Position (TP) sensor, which is mounted on the throttle body. The TP sensor provides feedback to the ECM. This feedback allows the ECM to appropriately control the throttle actuator and monitor the throttle opening angle as the ECM responds to driver inputs.

HINT

This ETCS (Electronic Throttle Control System) does not use a throttle cable.

The ECM monitors the electrical current through the electronic actuator, and detects malfunctions and open circuits in the throttle actuator based on this value. If the current is outside the standard range, the ECM determines that there is a malfunction in the throttle actuator. In addition, if the throttle valve does not function properly (for example, stuck on), the ECM determines that there is a malfunction. The ECM then illuminates the MIL and sets a DTC.

1. Example: When the electrical current is more than 10 A, or less than 0.5 A and the throttle actuator duty ratio is 80% or more, the ECM interprets this as the current being outside the standard range, and illuminates the MIL and sets a DTC. If the malfunction is not repaired successfully, a DTC is set when the engine is quickly revved to a high rpm several times after the engine has idled for 5 seconds after engine start.

The throttle actuator is operated by the ECM, and opens and closes the throttle valve using gears. The opening angle of the throttle valve is detected by the Throttle Position (TP) sensor, which is mounted on the throttle body. The TP sensor provides feedback to the ECM. This feedback allows the ECM to appropriately control the throttle actuator and monitor the throttle opening angle as the ECM responds to driver inputs.

HINT

This ETCS (Electronic Throttle Control System) does not use a throttle cable.

The ECM determines that there is a malfunction in the ETCS when the throttle valve remains at a fixed angle despite a high drive current from the ECM. The ECM illuminates the MIL and sets a DTC.

If the malfunction is not repaired successfully, a DTC is set when the accelerator pedal is fully depressed and released quickly (to fully open and close the throttle valve) after the engine is next started.

The ETCS (Electronic Throttle Control System) has a dedicated power supply circuit. When the monitored voltage (+BM) is low (less than 4 V), the ECM determines that there is a malfunction in the ETCS and cuts off the current to the throttle actuator.

When the voltage becomes unstable, the ETCS itself becomes unstable. For this reason, when the voltage is low, the current to the throttle actuator is cut. If repairs are made and the system returns to normal, turn the engine switch off. The ECM then allows the current to flow to the throttle actuator so that it can be restarted.

HINT

The ETCS does not use a throttle cable.

Scheme 49

The ECM monitors the battery supply voltage applied to the throttle actuator.

When the power supply voltage (+BM) drops below 4 V for 0.8 seconds or more, the ECM interprets this as an open in the power supply circuit (+BM). The ECM illuminates the MIL and sets the DTC.

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

The Electronic Throttle Control System (ETCS) is composed of the throttle actuator, Throttle Position (TP) sensor, Accelerator Pedal Position (APP) sensor, and ECM. The ECM operates the throttle actuator to regulate the throttle valve in response to driver inputs. The TP sensor detects the opening angle of the throttle valve, and provides the ECM with feedback so that the throttle valve can be appropriately controlled by the ECM.

The ECM determines the actual opening angle of the throttle valve from the TP sensor signal. The actual opening angle is compared to the target opening angle commanded by the ECM. If the difference between these two values is outside the standard range, the ECM interprets this as a malfunction in the ETCS. The ECM then illuminates the MIL and sets the DTC.

If the malfunction is not repaired successfully, the DTC is set when the accelerator pedal is quickly released (to close the throttle valve) after the engine speed reaches 5000 rpm by fully depressing the accelerator pedal (to fully open the throttle valve).

This ETCS (Electronic Throttle Control System) does not use a throttle cable.

The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal bracket and has 2 sensor circuits: VPA (main) and VPA2 (sub). This sensor is a non-contact type, and 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 voltage, which is applied to terminals VPA and VPA2 of the ECM, varies between 0 V and 5 V in proportion to the operating angle of the accelerator pedal (throttle valve). A signal from VPA indicates the actual accelerator pedal opening angle (throttle valve opening angle) and is used for engine control. A signal from VPA2 conveys the status of the VPA circuit and is used to check the APP sensor itself.

The ECM monitors the actual accelerator pedal opening angle (throttle valve opening angle) through the signals from VPA and VPA2, and controls the throttle actuator according to these signals.

Scheme 50

HINT

When any of these DTCs are set, check the APP sensor voltage by selecting the following menu items on the Techstream: Powertrain / Engine and ECT / Data List / Accelerator Position No. 1 and No. 2.

HINT

1. Accelerator pedal positions are expressed as voltages.
2. AP stands for Accelerator Pedal.

1. When either of the output voltages of VPA or VPA2 deviates from the standard range, or the difference between the output voltages of the 2 sensor circuits is less than the threshold, the ECM determines that there is a malfunction in the APP sensor. The ECM then illuminates the MIL and sets a DTC. Example: When the output voltage of VPA drops below 0.4 V for more than 0.5 seconds when the accelerator pedal is fully depressed, DTC P2122 is set. If the malfunction is not repaired successfully, a DTC is set 2 seconds after the engine is next started.

This ETCS (Electronic Throttle Control System) does not use a throttle cable.

The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal bracket and has 2 sensor circuits: VPA (main) and VPA2 (sub). This sensor is a non-contact type, and 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 voltage, which is applied to terminals VPA and VPA2 of the ECM, varies between 0 V and 5 V in proportion to the operating angle of the accelerator pedal (throttle valve). A signal from VPA indicates the actual accelerator pedal opening angle (throttle valve opening angle) and is used for engine control. A signal from VPA2 conveys the status of the VPA circuit and is used to check the APP sensor itself.

The ECM monitors the actual accelerator pedal opening angle (throttle valve opening angle) through the signals from VPA and VPA2, and controls the throttle actuator according to these signals.

The accelerator pedal position sensor is mounted on the accelerator pedal bracket. The accelerator pedal position sensor has 2 sensor elements and 2 signal outputs: VPA and VPA2. VPA is used to detect the actual accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA. When the difference between the output voltages of VPA and VPA2 deviates from the standard, the ECM determines that the accelerator pedal position sensor is malfunctioning. The ECM turns on the MIL and the DTC is set.

HINT

1. Although the DTC titles include oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
2. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.

The A/F 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 A/F sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.

The A/F sensor is the planar type and is integrated with the 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, 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 TWC 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 level.

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

Scheme 51

HINT

1. DTCs P2195 and P2196 indicate malfunctions related to the bank 1 A/F sensor circuit.
2. DTCs P2197 and P2198 indicate malfunctions related to the bank 2 A/F sensor circuit.
3. Bank 1 refers to the bank that includes No. 1 cylinder.
4. Bank 2 refers to the bank that includes No. 2 cylinder.
5. When any of these DTCs are set, check the A/F sensor output voltage by selecting the following menu items on the Techstream: Powertrain / Engine and ECT / Data List / AFS Voltage B1 S1.
6. Short-term fuel trim values can also be read using the Techstream.
7. The ECM regulates the voltages at the A1A+, A2A+, A1A- and A2A- terminals of the ECM to a constant level. Therefore, the A/F sensor output voltage cannot be confirmed without using the Techstream.
8. If a A/F sensor malfunction is detected, the ECM sets a DTC.

Sensor voltage detection monitor

Under the air fuel ratio feedback control, if the A/F sensor voltage output indicates rich or lean for a certain period of time, the ECM determines that there is a malfunction in the A/F sensor. The ECM illuminates the MIL and sets a DTC.

Example

If the A/F sensor voltage output is less than 2.8 V (very rich condition) for 5 seconds, even if the HO2 sensor voltage output falls from 0.59 V or more to less than 0.21 V, the ECM sets DTC P2196 or P2198. Alternatively, if the A/F sensor voltage output is more than 3.8 V (very lean condition) for 5 seconds, even if the HO2 sensor voltage rises from less than 0.21 V to 0.59 V or more, DTC P2195 or P2197 is set.

Sensor current detection monitor

A rich air fuel mixture causes a low A/F sensor current, and a lean air fuel mixture causes a high A/F sensor current. Therefore, the sensor output becomes low during acceleration, and it becomes high during deceleration with the throttle valve fully closed. The ECM monitors the A/F sensor current during fuel-cut and detects any abnormal current values.

If the A/F sensor output is 3.6 mA or more for more than 3 seconds of cumulative time, the ECM interprets this as a malfunction in the A/F sensor and sets DTC P2195 or P2197 (high-side stuck). If the A/F sensor output is 0.78 mA or less for more than 3 seconds of cumulative time, the ECM sets DTC P2196 or P2198 (low-side stuck).

Scheme 52

HINT

1. Although the DTC titles say oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
2. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.

These DTCs are set when there is an open or short in the A/F sensor circuit, or if A/F sensor output drops. To detect these problems, the voltage of the A/F sensor is monitored when turning the engine switch to the on (IG) position, and the admittance (admittance is an electrical term that indicates the ease of flow of current) is checked while driving. If the voltage of the A/F sensor is between 0.6 V and 4.5 V, it is considered normal. If the voltage is out of the specified range, or the admittance is less than the standard value, the ECM will determine that there is a malfunction in the A/F sensor. If the same malfunction is detected in the next driving cycle, the MIL will be illuminated and a DTC will be stored.

The A/F sensor, which is located between the exhaust manifold and catalyst, consists of alloyed metal elements and a heater.

Depending on the engine operating conditions, the heater heats the sensor elements to activate them. Battery voltage is applied to the heater, and the sensor ground is controlled by the ECM using a duty ratio.

The sensor elements convert the oxygen concentration in the exhaust gas into voltage values to output. Based on the voltage, the ECM determines the air fuel ratio and regulates the fuel injection volume depending on the air fuel ratio and engine operating conditions. The voltage changes between 0.6 V and 4.5 V while the engine is running. If the air fuel ratio is lean, which means the oxygen concentration in the exhaust gas is high, the voltage is high. If the air fuel ratio is rich, which means the oxygen concentration in the exhaust gas is low, the voltage is low.

Scheme 53

These DTCs are output when there is an open or short in the A/F sensor circuit, or if A/F sensor output drops. To detect these problems, the voltage of the A/F sensor is monitored when turning the engine switch to the on (IG) position, and the admittance (admittance is an electrical term that indicates the ease of flow of current) is checked while driving. If the voltage of the A/F sensor is between 0.6 V and 4.5 V, it is considered normal. If the voltage is out of the specified range, or the admittance is less than the standard value, the ECM will determine that there is a malfunction in the A/F sensor. If the same malfunction is detected in the next driving cycle, the MIL will be illuminated and a DTC will be stored.

The description can be found in the EVAP (Evaporative Emission) System. Refer to DESCRIPTION.

5 hours* after the engine switch is turned off, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.

HINT

*: If the engine coolant temperature is not below 35°C (95°F) 5 hours after the engine switch is turned off, the monitor check starts 2 hours later. If it is still not below 35°C (95°F) 7 hours after the engine switch is turned off, the monitor check starts 2.5 hours later.

*: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize.

P2420: Vent valve stuck open (vent)

In operation C, the vent valve turns ON (closes) and the EVAP system pressure is then measured by the ECM, using the canister pressure sensor, to conduct an EVAP leak check. If the pressure does not increase when the vent valve is open, the ECM interprets this as the vent valve being stuck open. The ECM illuminates the MIL and sets the DTC.

Scheme 54

To ensure the accuracy of the EVAP (Evaporative Emission) monitor values, the soak timer, which is built into the ECM, measures 5 hours (+/- 15 minutes) from when the engine switch is turned off, before the monitor is run. This allows the fuel to cool down, which stabilizes the Fuel Tank Pressure (FTP). When 5 hours have elapsed, the ECM turns on.

Scheme 55

5 hours after the engine switch is turned off, the soak timer activates the ECM to begin the EVAP system monitor. While the engine is running, the ECM monitors the synchronization of the soak timer and the CPU clock. If these two are not synchronized, the ECM interprets this as a malfunction, illuminates the MIL and sets the DTC (2 trip detection logic).

HINT

1. DTC P2A00 indicates malfunctions related to the bank 1 A/F sensor.
2. DTC P2A03 indicates malfunctions related to the bank 2 A/F sensor.
3. Bank 1 refers to the bank that includes No. 1 cylinder.
4. Bank 2 refers to the bank that includes No. 2 cylinder.
5. Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.

The A/F 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 A/F sensor malfunctions, the ECM is unable to control the air fuel ratio accurately.

The A/F sensor is the planar type and is integrated with the 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, 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 TWC 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 level.

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

After the engine is warmed up, the ECM performs air fuel ratio feedback control to maintain the air fuel ratio at the stoichiometric level. In addition, active A/F ratio control is performed for approximately 10 seconds after preconditions are met in order to measure the Control the Injection Volume for A/F Sensor response rate. During active A/F ratio control, the ECM forcibly increases and decreases the injection volume a certain amount, based on the stoichiometric air fuel ratio learned during normal air fuel ratio control, and measures the Control the Injection Volume for A/F Sensor response rate. The ECM receives a signal from the Control the Injection Volume for A/F Sensor while performing active A/F ratio control and uses it to calculate the Control the Injection Volume for A/F Sensor response rate deterioration level.

If the value for Control the Injection Volume for A/F Sensor response rate deterioration level is less than the threshold, the ECM interprets this as a malfunction and sets the DTC.

Scheme 56

The ECM (engine control unit) and the TCM (transmission control unit) are located inside the ECM. The ECM intercommunicates with the TCM through the CAN (controller area network).

If there is a problem in this intercommunication, the ECM sets the DTC.

When the engine switch is turned on (IG), the battery voltage is applied to terminal IGSW of the ECM. The ECM MREL output signal causes a current to flow to the coil, closing the contacts of the EFI MAIN relay and supplying power to terminal +B of the ECM.

If the engine switch is turned off, the ECM holds the EFI MAIN relay ON for a maximum of 2 seconds to allow for the initial setting of the throttle valve.

When the engine switch is turned on (IG), voltage from the ECM's MREL terminal is applied to the integration relay (EFI MAIN relay). This causes the contacts of the integration relay (EFI MAIN relay) to close, which supplies power to terminal +B or +B1 of the ECM.

Scheme 57

Scheme 58

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Scheme 63

Scheme 64

Scheme 65

Scheme 66

1. INSPECT ECM (+B, +B1 VOLTAGE) Turn the engine switch on (IG). Measure the voltage according to the value(s) in the table below. Standard voltage Tester Connection Specified Condition A6-6 (+B) - E7-7 (E1) 9 to 14 V A6-5 (+B1) - E7-7 (E1) 9 to 14 V OK --> PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE NG: Go to next step
2. CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND) Disconnect the E7 ECM connector. Measure the resistance according to the value(s) in the table below. Standard resistance (Check for open) Tester Connection Specified Condition E7-7 (E1) - Body ground Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
3. INSPECT ECM (IGSW VOLTAGE) Turn the engine switch on (IG). Measure the voltage according to the value(s) in the table below. Standard voltage Tester Connection Specified Condition A6-17 (IGSW) - E7-7 (E1) 9 to 14 V OK --> See step 6 NG: Go to next step
4. CHECK FUSE (IGN FUSE) Remove the IGN fuse from the cowl side junction block RH. Measure the resistance of the IGN fuse. Standard resistance Below 1 ohms NG --> CHECK FOR SHORT IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE OK: Go to next step
5. INSPECT IG2 RELAY Remove the IG2 relay from the engine room No. 2 relay block. Measure the resistance according to the value(s) in the table below. Standard resistance Tester Connection Specified Condition 3 - 5 10 kohms or higher 3 - 5 Below 1 ohms (when battery voltage applied to terminals 1 and 2) NG --> REPLACE IG2 RELAY OK --> GO TO SMART ACCESS SYSTEM WITH PUSH-BUTTON START
6. INSPECT ECM (MREL VOLTAGE) Turn the engine switch on (IG). Measure the voltage according to the value(s) in the table below. Standard voltage Tester Connection Specified Condition A6-13 (MREL) - E7-7 (E1) 9 to 14 V NG --> REPLACE ECM OK: Go to next step
7. CHECK FUSE (EFI FUSE) Remove the EFI fuse from the engine room No. 2 junction block. Measure the resistance of the EFI fuse. Standard resistance Below 1 ohms NG --> CHECK FOR SHORT IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE OK: Go to next step
8. INSPECT INTEGRATION NO. 1 RELAY (EFI MAIN RELAY) Remove the integration relay from the engine room No. 2 junction block. Measure the resistance according to the value(s) in the table below. Standard resistance Tester Connection Specified Condition 2C-1 - 2A-8 10 kohms or higher Below 1 ohms (when battery voltage applied to terminals 2A-6 and 2A-7) NG --> REPLACE INTEGRATION NO. 1 RELAY OK: Go to next step
9. CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY- ECM, INTEGRATION RELAY - BODY GROUND) Check the harness and the connectors between the integration relay and the ECM. Remove the integration relay from the engine room No. 2 junction block. Disconnect the A6 ECM connector. Measure the resistance according to the value(s) in the table below. Standard resistance (Check for open) Tester Connection Specified Condition 2A-6 - A6-13 (MREL) Below 1 ohms Standard resistance (Check for short) Tester Connection Specified Condition 2A-6 or A6-13 (MREL) - Body ground 10 kohms or higher Check the harness and the connectors between the integration relay and body ground. Remove the integration relay from the engine room No. 2 junction block. Measure the resistance according to the value(s) in the table below. Standard resistance (Check for open) Tester Connection Specified condition 2A-7 - Body ground Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> CHECK AND REPAIR HARNESS OR CONNECTOR (TERMINAL +B OF ECM - BATTERY POSITIVE TERMINAL)

The ECM constantly generates 5 V power from the battery voltage supplied to the +B (BATT) terminal to operate the microprocessor. The ECM also provides this power to the sensors through the VC output circuit.

Scheme 67

When the VC circuit is short-circuited, the microprocessor in the ECM and sensors that are supplied power through the VC circuit are inactivated because the power is not supplied from the VC circuit. Under this condition, the system does not start up and the MIL does not illuminate even if the system malfunctions.

HINT

Under normal conditions, the MIL is illuminated for several seconds when the engine switch is first turned on (IG). The MIL goes off when the engine is started.

Scheme 68

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Scheme 70

1. CHECK MIL Check that the Malfunction Indicator Lamp (MIL) lights up when turning the engine switch on (IG). OK MIL lights up. OK --> END NG: Go to next step
2. CHECK CONNECTION BETWEEN TECHSTREAM AND ECM Connect the Techstream to the DLC3. Turn the engine switch on (IG) and the Techstream on. Check the communication between the Techstream and ECM. Result Result Proceed to Communication is possible A Communication is not possible B A --> GO TO MIL CIRCUIT B: Go to next step
3. CHECK THROTTLE BODY ASSEMBLY (CHECK MIL ILLUMINATED) Disconnect the throttle body connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE THROTTLE BODY ASSEMBLY B: Go to next step
4. CHECK ACCELERATOR PEDAL ASSEMBLY (CHECK MIL ILLUMINATED) Disconnect the accelerator pedal position sensor connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE ACCELERATOR PEDAL ASSEMBLY B: Go to next step
5. CHECK VVT SENSOR FOR INTAKE SIDE BANK 1 (CHECK MIL ILLUMINATED) Disconnect the VVT sensor for intake side bank 1 connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE VVT SENSOR FOR INTAKE SIDE BANK 1 B: Go to next step
6. CHECK VVT SENSOR FOR EXHAUST SIDE BANK 1 (CHECK MIL ILLUMINATED) Disconnect the VVT sensor for exhaust side bank 1 connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE VVT SENSOR FOR EXHAUST SIDE BANK 1 B: Go to next step
7. CHECK VVT SENSOR FOR INTAKE SIDE BANK 2 (CHECK MIL ILLUMINATED) Disconnect the VVT sensor for intake side bank 2 connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE VVT SENSOR FOR INTAKE SIDE BANK 2 B: Go to next step
8. CHECK VVT SENSOR FOR EXHAUST SIDE BANK 2 (CHECK MIL ILLUMINATED) Disconnect the VVT sensor for exhaust side bank 2 connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE VVT SENSOR FOR EXHAUST SIDE BANK 2 B: Go to next step
9. CHECK FUEL PRESSURE SENSOR (CHECK MIL ILLUMINATED) Disconnect the fuel pressure sensor connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE FUEL PRESSURE SENSOR B: Go to next step
10. CHECK CANISTER ASSEMBLY (CHECK MIL ILLUMINATED) Disconnect the canister pump module connector. Turn the engine switch on (IG). Check the MIL. Result Result Proceed to MIL illuminates A MIL does not illuminate B A --> REPLACE CANISTER ASSEMBLY B: Go to next step
11. CHECK HARNESS AND CONNECTOR Disconnect the E39 throttle body connector. Disconnect the A34 accelerator pedal position sensor connector. Disconnect the E50 VVT sensor for intake side bank 1 connector. Disconnect the E58 VVT sensor for exhaust side bank 1 connector. Disconnect the E60 VVT sensor for intake side bank 2 connector. Disconnect the E66 VVT sensor for exhaust side bank 2 connector. Disconnect the E72 fuel pressure sensor connector. Disconnect the V17 canister pump module connector. Disconnect the E8, E45, A7 and A6 ECM connectors. Measure the resistance according to the value(s) in the table below. Standard resistance (Check for short) Tester Connection Specified Condition E8-27 (VCTA) - Body ground 10 kohms or higher E8-23 (VCV1) - Body ground 10 kohms or higher E8-20 (VCV2) - Body ground 10 kohms or higher E45-31 (VCPR) - Body ground 10 kohms or higher E45-22 (VCE1) - Body ground 10 kohms or higher E45-19 (VCE2) - Body ground 10 kohms or higher A7-35 (VCPA) - Body ground 10 kohms or higher A7-27 (VCP2) - Body ground 10 kohms or higher A6-22 (VCPP) - Body ground 10 kohms or higher Reconnect the throttle body connector. Reconnect the accelerator pedal position sensor connector. Reconnect the VVT sensor for intake side bank 1 connector. Reconnect the VVT sensor for exhaust side bank 1 connector. Reconnect the VVT sensor for intake side bank 2 connector. Reconnect the VVT sensor for exhaust side bank 2 connector. Reconnect the fuel pressure sensor connector. Reconnect the canister pump module connector. Reconnect the ECM connectors. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE ECM

Refer to DTC P0230 Refer to DESCRIPTION.

The cranking holding control system provides current to the starter when the ECM detects the engine switch's start signal (STSW). When the ECM performs a firing judgment, the system cuts current to the starter. When the ECM receives the STSW signal, it turns on the ST CUT relay, which prevents flickering of the combination meter, clock, audio system, etc. Also, the ECM sends a signal to the ECM's STAR terminal. Then the STAR output signal travels through the park/neutral position (PNP) switch to the STARTER relay, causing the starter to activate.

When the engine is cranking, the starter operation signal is sent to the ECM's STA terminal.

Scheme 71

The MIL (Malfunction Indicator Lamp) is used to indicate vehicle malfunction detected by the ECM.

By turning the engine switch on (IG), power is supplied to the MIL circuit, and the ECM provides the circuit ground which illuminates the MIL.

The MIL operation can be checked visually: When the engine switch is first turned on (IG), the MIL should be illuminated and should then turn OFF. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the Techstream.

Scheme 72

Scheme 73

1. CHECK THAT MIL IS ILLUMINATED Perform troubleshooting in accordance with the chart below. Result MIL Condition Proceed to MIL remains ON A MIL does not illuminate B B --> See step 6 A: Go to next step
2. CHECK WHETHER MIL TURNS OFF Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Check whether any DTCs have been stored Refer to «DTC CHECK / CLEAR»(ref-382723-S32023580312011012800000). Note them down if necessary. Clear DTCs Refer to «DTC CHECK / CLEAR»(ref-382723-S32023580312011012800000). Check if the MIL turns OFF. OK MIL should turn OFF. OK --> See step 4 NG: Go to next step
3. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT IN WIRE HARNESS) Disconnect the A7 ECM connector. Turn the engine switch on (IG). Check that the MIL is not illuminated. OK MIL is not illuminated. OK --> See step 5 NG --> CHECK AND REPAIR HARNESS AND CONNECTOR (COMBINATION METER - ECM)
4. REPAIR CIRCUITS INDICATED BY OUTPUT DTCSRefer to «DIAGNOSTIC TROUBLE CODE CHART»(ref-382723-S22399221492011012800000)
5. REPLACE ECMRefer to «REMOVAL»(ref-382728-S20466676072011012800000)
6. CHECK THAT MIL IS ILLUMINATED Check if the MIL is illuminated when the engine switch is turned on (IG). OK MIL should be illuminated. OK --> SYSTEM OK NG: Go to next step
7. CHECK THAT ENGINE STARTS Turn the engine switch on (IG). Start the engine. Result Result Proceed To Engine starts A Engine does not start* B HINT: *: Techstream cannot communicate with the ECM. B --> See step 9 A: Go to next step
8. INSPECT COMBINATION METER (MIL CIRCUIT) See the combination meter troubleshooting procedure Refer to «HOW TO PROCEED WITH TROUBLESHOOTING»(ref-382731-S07715468002011012800000). NG --> REPAIR OR REPLACE BULB OR COMBINATION METER ASSEMBLY OK --> CHECK AND REPAIR HARNESS AND CONNECTOR (COMBINATION METER - ECM)
9. GO TO VC OUTPUT CIRCUIT. Refer to «VC Output Circuit»(ref-382724-S09466728742011012800000)

See also:
• COMPONENTS
• REMOVAL
• INSPECTION
• ON-VEHICLE INSPECTION