Engine Control (Sfi) System (Dtcs P0420 - U0101 & Circuit Tests): Overview Lexus IS II facelift

MONITOR DESCRIPTION

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 cylinder No. 1.
2. Bank 2 refers to the bank that does not include cylinder No. 1.
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.

DESCRIPTION

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

5 hours* after the engine switch is turned off, the electric vacuum pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) 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.

HINT

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

Scheme 35

Scheme 36

1. The leak defection pump creates negative pressure through the reference orifice. When the system is normal, the EVAP pressure 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 is this malfunction is detected in consecutive drive cycles. *: Typical value.

The circuit 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 37

Scheme 38

Scheme 39

1. KEY-OFF MONITOR 5 hours* after the engine switch is turned off, the electric vacuum pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) 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 hours (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 70 kPa and 110 kPa (525 mmHg and 825 mmHg), ECM cancels EVAP system monitor. 10 seconds B First 0.02 inch leak pressure measurement In order to determine 0.02 inch leak pressure standard, vacuum pump creates negative pressure (vacuum) through 0.02 inch orifice and then ECM checks if vacuum 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 they will be used in leak check. If EVAP pressure does not stabilize within 15 minutes, ECM cancels EVAP system monitor. 15 seconds* D EVAP VSV monitor EVAP VSV opened and then EVAP system pressure measured by ECM. Large increase indicates normal. 10 seconds E Second 0.02 inch leak pressure measurement After second 0.02 inch leak pressure measurement, leak check performed by comparing first and second 0.02 inch leak pressure standards. If stabilized system pressure higher than second 0.02 inch leak pressure standard, ECM determines that EVAP system leaking. 60 seconds F Final check Atmospheric pressure measured and then monitoring result recorded by ECM. - HINT: *: If only a small amount of fuel is in the fuel tank, it takes longer for the EVAP pressure to stabilize. EVAP VSV stuck open In operation C, the vacuum pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) system. The EVAP system pressure is then measured by the ECM using the pressure sensor. If the stabilized system pressure is higher than [second 0.02 inch leak pressure standard x 0.2], the ECM interprets this as the EVAP VSV (Vacuum Switching Valve) being stuck open. The ECM illuminates the MIL and sets the DTC (2 trip detection logic). EVAP VSV stuck closed In operation D, the pressure sensor measures the EVAP (Evaporative Emission) system pressure. The pressure measurement for EVAP VSV monitor is begun when the EVAP VSV is turned ON (open) after the EVAP leak check. When the measured pressure indicates an increase of 0.3 kPa (2.25 mmHg) or more, the EVAP VSV is functioning normally. If the pressure does not increase, the ECM interprets this as the EVAP 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. The 1st monitor While the engine is running and the EVAP VSV (vacuum Switching Valve) 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. 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 EVAP VSV being stuck closed, and 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 pressure, before and after conduction of the purge flow monitor, is measured by the ECM.

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

Scheme 40

1. DTC P0450: Pressure sensor voltage abnormal fluctuation If the pressure sensor output voltage 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 pressure sensor or its circuit, and stops the EVAP (Evaporative Emission) system monitor. The ECM then illuminates the MIL and sets the DTC (1 trip detection logic).
2. DTC P0451: Pressure sensor noising or stuck If the pressure sensor output voltage fluctuates rapidly for 10 seconds, the ECM stops the EVAP system monitor. The ECM interprets this as noise from the pressure sensor, and stops the EVAP system monitor. The ECM then illuminates the MIL and sets the DTC. Alternatively, if the sensor output voltage 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 the malfunctions are detected by 2 trip detection logic).
3. DTC P0452: Pressure sensor voltage low If the pressure sensor output voltage is below 0.45 V, the ECM interprets this as an open or short circuit malfunction in the 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: Pressure sensor voltage high If the pressure sensor voltage output is 4.9 V or more, the ECM interprets this as an open or short circuit malfunction in the 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 circuit description can be found in the EVAP (Evaporative Emission) System. Refer to DESCRIPTION.

5 hours* after the engine switch is turned off, the electric vacuum pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) 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.

HINT

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

Scheme 41

1. P0455: EVAP (Evaporative Emission ) gross leak In operation C, the vacuum 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 0.02 inch leak pressure standard 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. P0456: EVAP very small leak In operation C, the vacuum 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 0.02 inch leak pressure standard, the ECM determines that the EVAP system has a small leakage, illuminates the MIL and sets the DTC (2 trip detection logic).

The speed sensor detects the wheel speed and sends the appropriate signals to the skid control ECU. The skid control ECU converts these wheel speed signals into a 4-pulse signal and outputs it to the ECM via the combination meter. The ECM determines the vehicle speed based on the frequency of these pulse signals.

Scheme 42

Manual Transaxle Models

The ECM assumes that the vehicle is being driven while the vehicle speed sensor signal is being transmitted by the combination meter. If there is no signal from the No. 1 vehicle speed sensor despite this condition being met, the ECM interprets this as a malfunction in the sensor. The ECM then illuminates the MIL and sets the DTC.

The stop light switch is a duplex system that transmits two 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 conditions are as shown in the table below. The signals can be read using Techstream.

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 and the MIL comes on and the ECM stores the DTC. The vehicle must stop (less than 2 mph (3 km/h)) and go (19 mph (30 km/h) or more) 5 times for two driving cycles in order to detect a malfunction.

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; 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

1. The learned idling air flow volume remains at the maximum or minimum 5 times or more during a driving cycle
2. After driving at 6 mph (10 km/h) or more, the actual engine idling speed varies from the target idling speed by between 100 RPM and 200 RPM, 5 times or more during a driving cycle.

1. Example: If the actual idling speed varies from the target idling speed by more than 200 RPM* 5 times during a driving cycle, the ECM illuminates the MIL and sets the DTC.

HINT

*: Threshold idling speed varies with engine load.

Scheme 43

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

In addition, the ECM retards the ignition timing and the ETCS increases the intake air amount to quickly increase the catalyst temperature at cold start to reduce emissions.

Scheme 44

The ECM monitors the intake air amount during idling and the ignition timing.

When the Engine Coolant Temperature (ECT) is between -10°C and 50°C (14°F and 122°F), the ECM calculates the idling intake air amount for 10 seconds, beginning 3 seconds after the engine starts.

When the accumulated value is below the threshold, the ECM interprets this as a malfunction in the Idle Speed Control (ISC) system at cold start.

The ECM also monitors the ignition timing at cold start, and judges it to be incorrect when it is advanced to the same value for a warm engine for 5 seconds or more of the 10 second monitoring period.

Example

P050A is detected when all conditions below are met (2 trip detection logic).

1. The ECT is between -10°C and 50°C (14°F and 122°F) when the engine starts.
2. The engine idles for 13 seconds after engine start.
3. The accumulated intake air amount is below the threshold.

The ECM sets the DTC and illuminates the MIL 13 seconds after the engine is next started.

Note. When the negative battery terminal is disconnected during inspection or repairs, the ISC learning values are cleared. The ISC learning must be performed by warming up the engine and idling for 5 minutes with the ECT at 75°C (167°F) or more because DTCs cannot be detected with the ISC learning values cleared.

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 set after the engine 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 lower than 50°C (122°F) of the engine coolant temperature, the ECM measures the accumulated mass air flow at the engine 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 cleared.

Scheme 45

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

The ECM continuously monitors its internal processors (CPUs), heated oxygen sensor transistors. This self-check ensures that the ECM is functioning properly.

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

The ECM also monitors the cruise control cancel circuit. If this circuit malfunctions, the ECM will set a 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 Techstream.

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

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 high pressure side fuel pump 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, 580 to 1885 psi) according to the operating condition, and it feeds the fuel to the fuel delivery pipe.

The Swirl Control Valve (SCV) is built into the intake manifold. The SCV consists of the position sensor and a DC motor. The SCV is attached to one side of the independent intake port. Depending on signals from the ECM, the DC motor opens and closes the SCV. The position sensor detects the opening angle of the SCV. When the SCV closes, the intake air flow velocity that will pass through the port on the other side of the independent intake port will become faster, which causes the lateral turbulence of the fuel in the fuel tank to strengthen. As a result, when engine coolant temperature is low, the fuel's atoms accelerate and the fuel's stability increases. Also, when the engine is running with a light load, the fuel efficiency increases, decreasing fuel consumption.

When the ECM has requested an SCV close operation but the SCV's actual opening angle is more than 20° for 1 second, DTC P2004 is output. When the ECM has requested an SCV open operation but the SCV's actual opening angle is less than 35° for 1 second, DTC P2006 is output.

HINT

After confirming DTCs P2004 and/or P2006, use Techstream to confirm the SCV ANG SENS D4 (SCV position sensor output voltage) while performing the SCV DUTY RATIO (DC Motor for SCV) of the Active Test.

REFERENCE VOLTAGE (NORMAL CONDITION)

The ECM activates the DC motor for Swirl Control Valve (SCV), which opens and closes SCV. The ECM activates the DC motor based on engine RPM, coolant temperature, engine load signals and other conditions. When the voltage of the DC motor deviates from the standard range, the ECM determines that a malfunction has occurred and outputs a DTC.

The Swirl Control Valve (SCV) position sensor is a non-contact type.

The position sensor measures the opening angle of the SCV. The sensor is reliable and accurate, as it is electrically controlled by Hall elements.

The ECM's IAC1 terminal voltage increases in correlation with the opening angle of the SCV. When the SCV is fully closed, approximately 0.6 V is applied to the IAC1 terminal. When the SCV is fully open, approximately 3.6 V is applied to the IAC1 terminal.

When the output voltage of the IAC1 terminal deviates from the standard range, the ECM determines that a malfunction has occurred in the position sensor and outputs a DTC.

Scheme 46

HINT

After confirming DTC P2014, P2016 or P2017, use Techstream to confirm the SCV ANG SENS D4 (SCV position sensor output voltage) from Powertrain / Engine and ECT / Data List.

SYSTEM DESCRIPTION

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 less than 0.5 A and the throttle actuator duty ratio exceeds 80%, 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 is stated and has idled for 5 seconds.

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 47

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 (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 48

HINT

When any of these DTCs are set, check the APP sensor voltage by entering the following menus on Techstream: Powertrain / Engine and ECT / Data List / Accel Sensor Out No. 1 and Accel Sensor Out No. 2.

HINT

1. Accelerator pedal positions are expressed as voltages.
2. AP denotes 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.

HINT

When any of these DTCs are set, check the APP sensor voltage by entering the following menus on Techstream: Powertrain / Engine and ECT / Data List / Accel Sensor Out No. 1 and Accel Sensor Out No. 2.

HINT

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

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 a 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 though 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 49

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 cylinder No. 1.
4. Bank 2 refers to the bank that includes cylinder No. 2.
5. When any of these DTCs are set, check the A/F sensor output voltage by entering the following menus on Techstream: Powertrain / Engine and ECT / Data List / A/F Control System / AFS Voltage B1 S1 or AFS Voltage B2 S1.
6. Short-term fuel trim values can also be read using 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 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, despite the HO2 sensor voltage output fails 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, despite 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 50

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 turn the engine switch On (IG), 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 0.6V and 4.5V, 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 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, 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 0.6V and 4.5V 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 51

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 turn the engine switch On (IG), 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 0.6V and 4.5V, 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 next driving cycle, the MIL will be illuminated and a DTC will be stored.

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

5 hours* after the engine switch is turned off, the electric vacuum pump creates negative pressure (vacuum) in the EVAP (Evaporative Emission) 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.

HINT

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

In operation C, the vent valve turns ON (closes) and the EVAP (Evaporative Emission) system pressure is then measured by the ECM using the pressure sensor to conduct an EVAP leak check. If 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 52

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 53

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 cylinder No. 1.
4. Bank 2 refers to the bank that includes cylinder No. 2.
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 though 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 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 A/F sensor response rate. The ECM receives a signal from the A/F sensor while performing active A/F ratio control and uses it to calculate the A/F sensor response rate deterioration level.

If the value 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 54

The engine control unit and the transmission control unit are located inside the ECM. The engine control unit intercommunicates with the transmission control ECU through the Controller Area Network (CAN).

If there is a problem in this intercommunication, the ECM sets a 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 and +B1 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 applies 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.

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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 +B (A5-6) - E1 (E4-7) 9 to 14 V +B1 (A5-5) - E1 (E4-7) 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 E4 ECM connector. Measure the resistance according to the value(s) in the table below. Standard resistance (Check for open) Tester Connection Specified Condition E1 (E4-7) - Body ground Below 1 ohms Reconnect the ECM connector. 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 IGSW (A5-17) - E1 (E4-7) 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 Reinstall the IGN fuse. NG --> REPLACE FUSE OK: Go to next step
5. INSPECT IGNITION RELAY NO. 2 Remove the IG2 relay from the engine room R/B No. 2. 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 IGNITION RELAY NO. 2 OK --> CHECK AND REPLACE 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 MREL (A5-13) - E1 (E4-7) 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 J/B No. 2. Measure the resistance of the EFI fuse. Standard resistance Below 1 ohms Reinstall the EFI fuse. NG --> REPLACE FUSE OK: Go to next step
8. INSPECT INTEGRATION NO. 1 RELAY (EFI MAIN RELAY) Remove the integration relay from the engine room J/B No. 2. Measure the resistance according to the value(s) in the table below. Standard resistance Tester Connection Specified Condition 2A-5 - 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 J/B No. 2. Disconnect the A5 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 - MREL (A5-13) Below 1 ohms Standard resistance (Check for short) Tester Connection Specified Condition 2A-6 or MREL (A5-13) - 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 J/B No. 2. 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 AND CONNECTOR (TERMINAL +B OF ECM - BATTERY POSITIVE TERMINAL)

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

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.

Refer to DTC P0230. Refer to DTC P0230: Fuel Pump Primary Circuit.

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 an 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 (A/T) or clutch pedal switch (M/T) 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 67

The cold start injector is attached to the intake air surge tank and is designed to improve startability when the engine is cold. It operates when the engine coolant temperature is -12°C or less, and the starter signal is ON.

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1. INSPECT COLD START INJECTOR Disconnect the E57 cold start injector connector. Measure the resistance according to the value(s) in the table below. Standard resistance Tester Connection Condition Specified Condition 1 - 2 20°C (68°F) 11.6 to 12.6 ohms NG --> REPLACE COLD START INJECTOR OK: Go to next step
2. INSPECT ECM (STJ1 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 STJ1 (E3-7) - E1 (E4-7) 9 to 14 V OK --> REPLACE ECM NG: Go to next step
3. CHECK HARNESS AND CONNECTOR (COLD START INJECTOR - ECM) Disconnect the E57 cold start injector connector. Disconnect the E3 ECM connector. Measure the resistance according to the value(s) in the table below. Standard (Check for open) Tester Connection Specified condition E57-1 - STJ1 (E3-7) Below 1 ohms Standard (Check for short) Tester Connection Specified condition E57-1 or STJ1 (E3-7) - Body ground 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> CHECK AND REPLACE HARNESS AND CONNECTOR (COLD START INJECTOR - BATTERY POSITIVE TERMINAL)

When the Intake Air Control Valve (IACV) opens and closes, the ACIS control circuit causes the engine load intake efficiency to increase. When the engine is running at 2450 to 4100 RPM and the throttle valve opening angle is 30° or more, current flows through the ACIS control circuit and the IACV closes. For all other situations, current does not flow through the ECM and the IACV is open.

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1. PERFORM ACTIVE TEST USING TECHSTREAM (OPERATE INTAKE AIR CONTROL VALVE) Connect Techstream to the DLC3. Start the engine and turn the tester on. Enter the following menus: Powertrain / Engine and ECT / Active Test / Activate the VSV for Intake Control. Check if operating noise can be heard when operating the intake control valve using Techstream. OK Operating noise can be heard. OK --> CHECK FOR INTERMITTENT PROBLEMS NG: Go to next step
2. CHECK AIR INTAKE VALVE (OPERATION) Disconnect the VCV ACIS connector. Apply battery voltage between the terminals of the air intake valve connector. Check air intake valve operation. OK Operating noise can be heard. NG --> REPLACE INTAKE AIR SURGE TANK OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (VCV ACIS - ECM, VSV ACIS - EFI NO. 2 FUSE) Check the wire harness between the intake air control connector and the ECM connector. Disconnect the VCV ACIS connector. Disconnect the E5 ECM connector. Measure the resistance according to the value(s) in the table below. Standard resistance (Check for open) Tester Connection Specified Condition VCV ACIS (E50-2) - ACIS (E5-3) Below 1 ohms Standard resistance (Check for short) Tester Connection Specified Condition VCV ACIS (E50-2) or ACIS (E5-3) - Body ground 10 kohms or higher Check the wire harness between the VCV ACIS connector and the EFI No. 2 fuse. Disconnect the air intake valve connector. Remove the EFI No. 2 fuse from the engine room R/B No. 2. Measure the resistance according to the value(s) in the table below. Standard resistance (Check for open) Tester Connection Specified Condition VCV ACIS (E50-1) - EFI No. 2 fuse (2) of Engine room No. 2 relay block Below 1 ohms NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> REPLACE ECM

The MIL (Malfunction Indicator Lamp) is used to indicate malfunction detections 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 Techstream.

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See also:
• COMPONENTS
• ON-VEHICLE INSPECTION