Engine Control System (Diagnostic Codes (P0401-P1605)): Overview Lexus GX J150

DESCRIPTION

Based on the driving conditions, the ECM regulates the volume of exhaust gas that is recirculated to the engine's combustion chambers and thus lowers the combustion temperature to reduce NOx emissions. The ECM monitors signals such as engine speed, coolant temperature, electric load and vehicle speed. When the EGR permission conditions are fulfilled, the ECM controls the opening of the EGR valve linearly through signals to the EGR stepper motor.

MONITOR DESCRIPTION

The ECM monitors the pressure inside the intake manifold while opening and closing the EGR valve during fuel cut operation. If there is no change in the manifold absolute pressure sensor value, the ECM interprets this as a malfunction in the EGR valve assembly, illuminates the MIL and stores the DTC (2 trip detection logic).

Refer to DTC P0401. Refer to DESCRIPTION .

HINT

DTC P0403 is stored when the engine switch is on (IG).

This DTC is designed to detect an open or short in the EGR valve circuit.

If the EGR terminal voltage is low when the EGR terminal output is off, the ECM determines that the EGR valve circuit is malfunctioning.

The secondary air injection system injects air into the exhaust port of the cylinder head using an electric air pump, starting when the engine is started cold and operating until the catalyst warms up, in order to promote combustion of unburned fuel and decrease the amount of hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas.

Scheme 139

This DTC indicates an open or short circuit in the circuit containing the air switching valve of the secondary air injection system. The air injection control driver performs diagnosis of the air pump, air switching valve (bank 1) and itself, and sends the results of this diagnosis to the ECM as a duty signal. When the ECM receives a signal indicating a malfunction in the air pump, air switching valve or air injection control driver, it illuminates the MIL and stores a DTC.

The ECM operates the air injection VSV relay (AI-VSV) which causes the air switching valve (for bank 2) to operate.

These DTCs are designed to detect a malfunction in the air injection VSV (AI-VSV) relay circuit. When the system is normal, the battery voltage is applied to terminal AIR1 of the ECM while the air injection VSV (AI-VSV) relay is turned off, and the battery voltage is not applied to terminal AIR1 of the ECM while the air injection VSV (AI-VSV) relay is turned on. The ECM illuminates the MIL and stores a DTC when either one of the following conditions is detected.

1. The battery voltage is not applied to terminal AIR1 while the air injection VSV (AI-VSV) relay is off.
2. The battery voltage is applied to terminal AIR1 while the air injection VSV (AI-VSV) relay is on.

Refer to DTC P0412. Refer to DESCRIPTION .

This DTC indicates an open or short circuit in the circuit containing the air pump of the secondary air injection system. The air injection control driver performs diagnosis of the air pump, air switching valve and itself, and sends the results of this diagnosis to the ECM as a duty signal. When the ECM receives a signal indicating a malfunction in the air pump, air switching valve or air injection control driver, it illuminates the MIL and stores a DTC.

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 sensor, sends pre-catalyst information to the ECM. The second sensor, the heated oxygen sensor, sends post-catalyst information to the ECM.

In order to detect any deterioration in the Three-way Catalytic Converter (TWC), the ECM calculates the Oxygen Storage Capacity (OSC) of the Three-way Catalytic Converter (TWC). This calculation is based on the voltage output of the heated oxygen sensor while performing active air-fuel ratio control.

The OSC value is an indication of the oxygen storage capacity of the Three-way Catalytic Converter (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 the rich-lean cycle of the heated oxygen sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the heated oxygen sensor and Three-way Catalytic Converter (TWC).

The ECM uses the OSC value to determine the state of the Three-way Catalytic Converter (TWC). If any deterioration has occurred, it illuminates the MIL and stores the DTC.

Scheme 140

TEXT IN ILLUSTRATION

The description can be found in 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 141

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

*: Typical value.

Scheme 142

The description can be found in 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 143

Scheme 144

Scheme 145

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 70 kPa-a and 110 kPa-a (525 mmHg-a and 825 mmHg-a), ECM cancels EVAP system monitor. 60 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. 360 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 measurements. 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. - HINT: *: 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 stores 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 stores the DTC (2 trip detection logic).
2. Purge Flow Monitor The purge flow monitor consists of two 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 0.15 kPa-g (1.12 mmHg-g), the ECM interprets this as the purge VSV being stuck closed, and illuminates the MIL and stores DTC P0441 (2 trip detection logic).

Atmospheric pressure check

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

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

Scheme 146

1. DTC P0451: Canister pressure sensor noise If the canister pressure sensor voltage output fluctuates rapidly for 10 seconds, the ECM interprets this as noise from the canister pressure sensor and stops the EVAP system monitor. The ECM then illuminates the MIL and stores the DTC (2 trip detection logic).
2. DTC P0452: Canister pressure sensor voltage low If the canister pressure sensor output [pressure] is below 42.1 kPa-a (315.9 mmHg-a), 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 stores the DTC (1 trip detection logic).
3. DTC P0453: Canister pressure sensor voltage high If the canister pressure sensor output [pressure] is higher than 123.8 kPa-a (928.4 mmHg-a), 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 stores the DTC (1 trip detection logic).

The description can be found in 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 147

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 leak, illuminates the MIL and stores 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 leak, illuminates the MIL and stores 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 pulse signal and outputs it to the ECM via the combination meter. The ECM determines the vehicle speed based on the frequency of this pulse signal.

Scheme 148

The ECM assumes that the vehicle is being driven when the vehicle speed measured by the output speed sensor (SP2) is more than 9 km/h (5.6 mph). If there is no speed signal from the combination meter despite this condition being met, the ECM interprets this as a malfunction in the speed signal circuit. The ECM then illuminates the MIL and stores 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 stores 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 149

The idling speed is controlled by the ETCS (Electronic Throttle Control System). The ETCS is comprised of: 1) the 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 idling 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 either of the following conditions is met

1. The difference between the target engine idling speed and actual engine idling speed exceeds the threshold and the IAC flow rate learned value is stuck at the upper or lower limit for 5 seconds or more.
2. After driving at a vehicle speed of 10 km/h (6.25 mph) or more, the difference between the target and actual engine idling speed exceeds the threshold 5 times or more during a driving cycle, and then the system determines that the IAC flow rate learned value is stuck at the upper or lower limit, or that the IAC flow rate learned value has been changed by an amount that exceeds the threshold.

Scheme 150

This monitor will run when the engine is started with the engine coolant temperature at -10 to 50°C (14 to 122°F). The DTC will be stored after the engine idles 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 with the engine coolant temperature below 50°C (122°F), the ECM measures the accumulated mass air flow while the engine is idling. If it does not reach the threshold within 10 seconds, the ECM interprets this as a malfunction. The MIL is illuminated and a DTC is stored when the malfunction is detected in consecutive driving cycles (2 trip detection logic).

The ETCS (Electronic 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 cable is disconnected from the negative battery terminal during inspections or repairs, the ISC (Idle Speed Control) learned values are cleared. This DTC cannot be stored with the ISC learned values cleared.

HINT

ISC learning is performed when the engine is warmed up and has been idling for 5 minutes.

Scheme 151

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

The DTC is designed to monitor the ignition timing at cold start. When the engine is started at an engine coolant temperature of below 50°C (122°F), the ECM checks the ignition timing during engine idling. If the ignition timing advances beyond the specified level within 10 seconds, the ECM interprets this as a malfunction. The MIL is illuminated and a DTC is stored when the malfunction is detected in consecutive driving cycles (2 trip detection logic).

Note. When the cable is disconnected from the negative battery terminal during inspections or repairs, the ISC (Idle Speed Control) learned values are cleared. This DTC cannot be stored with the ISC learned values cleared.

HINT

ISC learning is performed when the engine is warmed up and has been idling for 5 minutes.

Scheme 152

The power steering oil pressure switch is turned on when a power steering wheel load is generated by turning the steering wheel. The ECM regulates the engine idling speed according to the voltage output of the sensor.

Scheme 153

The ECM monitors the switch voltage and uses this value to regulate the engine idling speed. When the sensor output voltage deviates from the normal operating range, the ECM determines that there is a malfunction in the power steering oil pressure switch and stores a DTC.

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, the memory is cleared and the ECM determines that there is a malfunction in the power supply circuit. When the engine is next started, the ECM illuminates the MIL and stores the DTC.

HINT

If DTC P0560 is stored, the ECM does not store other DTCs and the data stored in the ECM is partly cleared.

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

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 standard, the ECM will illuminate the MIL and store a DTC immediately.

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

The main CPU and sub CPU of the ECM perform data communication between each other. The main CPU monitors the communications and WDC pulses from the sub CPU. When the signal malfunctions below are detected, a DTC is stored.

This DTC is stored when a communication error occurs in the ECM.

The ECM monitors the input signals of the accelerator pedal position sensor No. 1. When the input signals and control signals deviate, a DTC is stored.

The ECM monitors the input signals of the throttle position sensor No. 1 and stop light switch. As the ECM monitors the input signals of the throttle position sensor No. 1 and the STP signals of the stop light switch, if the input signals and control signals deviate, a DTC is stored.

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 stores the DTC.

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

The ECM monitors its internal operation and stores this DTC when it detects an internal malfunction.

The ECM monitors its internal operation. If there is an internal operation malfunction, the ECM illuminates the MIL and stores a DTC.

DTC P0630 is stored when the Vehicle Identification Number (VIN) is not stored in the ECM or the input VIN is incorrect. The VIN is input 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 usually is 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 store a DTC when the engine switch is turned on (IG).

The stop light switch is part of a duplex system that transmits 2 signals: STP and ST1-. These 2 signals are used by the ECM to monitor whether or not the brake system is working properly. This DTC indicates that the stop light switch remains on. When the stop light switch remains on during GO and STOP driving, the ECM interprets this as a fault in the stop light switch. Then the MIL illuminates and the ECM stores the DTC.

This DTC indicates that the stop light switch remains on. When the stop light switch remains on during GO and STOP driving, the ECM interprets this as a fault in the stop light switch. Then the MIL illuminates and the ECM stores the DTC. The vehicle must GO (30 km/h (18.65 mph) or more) and STOP (less than 3 km/h (1.86 mph)) 5 times for 2 driving cycles in order for the DTC to be stored.

HINT

*: Name of Data List item

This DTC is stored when a deviation from pressure sensor characteristics is detected.

The pressure sensors* are checked 55 minutes after the engine switch is turned off. If the pressures detected by the pressure sensors* differ by a certain amount, the MIL is illuminated and a DTC is stored (2 trip detection logic).

HINT

1. *: P106A checks the canister pressure sensor and manifold absolute pressure sensor. P106B checks the canister pressure sensor and the pressure sensor of the air switching valves (Bank 1 and Bank 2).
2. Correct judgment may not be possible when the elevation is 4000 m (13120 ft.) or more.

The camshaft position sensor (G signal) consists of a magnet and MRE (Magnetoresistive Element).

The camshaft timing gear (LH) has 3 teeth on its outer circumference. When the camshaft timing gear rotates, the air gap between the protrusion on the gear and the MRE changes. The change affects the magnetic field and results in changes in the resistance of the MRE.

The crankshaft angle sensor rotor has 34 teeth and is mounted on the crankshaft. The crankshaft position sensor generates 34 signals per crankshaft revolution. The ECM uses the G2 signal to distinguish between the cylinders, and uses the NE signal to detect the crankshaft position and engine speed.

Scheme 154

1. Reference: Inspection using an oscilloscope. Standard Tester Connection Tool Setting Condition Specified Condition C28-6 (NE+) - C28-5 (NE-) 5 V/DIV., 20 msec./DIV. Cranking or idling The correct waveform is as shown C28-9 (G2) - C28-10 (G2-) 5 V/DIV., 20 msec./DIV. Cranking or idling The correct waveform is as shown HINT: G2 is the camshaft position sensor signal, and NE is the crankshaft position sensor signal.

If no signal is transmitted by the camshaft position sensor despite the engine running, or the rotations of the camshaft and crankshaft are not synchronized, the ECM interprets this as a malfunction of the sensor. Also, when the sensor output voltage remains below 0.3 V, or higher than 4.7 V for more than 4 seconds, the ECM stores a DTC.

P1603

After starting the engine, this DTC is stored when the engine stops without the engine switch being operated.

Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle has ran out of fuel before performing troubleshooting, as this DTC is also stored when the engine stalls due to running out of fuel.

P1605

This DTC is stored if the engine speed drops below the set speed.

Using the Techstream, the conditions present when the DTC was stored can be confirmed by referring to the freeze frame data. Freeze frame data records engine conditions when a malfunction occurs. This information can be useful when troubleshooting.

It is necessary to check if the vehicle ran out of fuel before performing troubleshooting, as this DTC is also stored when idling is unstable due to running out of fuel.

Scheme 155

Scheme 156

Scheme 157

1. Reference waveforms showing a normal cold engine start
2. Reference waveforms showing a normal warm engine start
3. Reference values when there is an air leak in the intake system (disconnect PCV hose) and P1605 is stored