Engine Control System (Diagnostic Codes (P0420-P1605)): Overview Scion xB II рестайлинг

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.

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 stores the DTC.

Scheme 208

DESCRIPTION

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

5 hours* after the ignition 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 ignition 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 ignition 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 209

TEXT IN ILLUSTRATION

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

*: Typical value.

Scheme 210

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 ignition switch is turned off. The purge flow monitor runs while the engine is running.

Scheme 211

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1. KEY-OFF MONITOR 5 hours* after the ignition 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 ignition 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 ignition 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 ignition 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(abs) and 110 kPa(abs) [525 mmHg(abs) and 825 mmHg(abs)], 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. 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. TEXT IN ILLUSTRATION *1 Purge VSV: OFF (closed) *2 Purge VSV: ON (open) *3 Vent Valve: OFF (vent) *4 Vent Valve: ON (closed) *5 Leak Detection Pump: OFF *6 Leak Detection Pump: ON *7 Reference Orifice (0.02 inch) *8 Canister Pressure Sensor *9 Canister *10 Fuel Tank *11 Canister Pump Module *12 Canister Filter *a Operation A: Atmospheric Pressure Measurement *b Operation B, E: Reference Leak Pressure Measurement *c Operation C: EVAP System Pressure Measurement *d Operation D: Purge VSV Monitor *e Atmospheric Pressure *f Negative Pressure 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 0.35], 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(gauge) [2.25 mmHg(gauge)] 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 0.4 kPa(gauge) [3.0 mmHg(gauge)], 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 the atmospheric pressures, before and after conduction of the purge flow monitor, is measured by the ECM.

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

Scheme 214

1. DTC P0451: Canister pressure sensor noise or fixed/flat 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 stores the DTC. Alternatively, if the sensor voltage output does not change for 10 seconds, the ECM interprets this as the sensor being fixed/flat, and stops the monitor. The ECM then illuminates the MIL and stores the DTC. (Both malfunctions are detected by 2 trip detection logic.)
2. DTC P0452: Canister pressure sensor voltage low If the canister pressure sensor voltage output [pressure] is below 0.45 V (42.1 kPa(abs) [315.7 mmHg(abs)]), 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 voltage output [pressure] is 4.9 V (123.8 kPa(abs) [928.5 mmHg(abs)]) 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 stores the DTC (1 trip detection logic).

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

5 hours* after the ignition 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 ignition 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 ignition 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.

TEXT IN ILLUSTRATION

Scheme 215

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 0.35] (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 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 216

Automatic Transaxle Models

The ECM assumes that the vehicle is being driven when the vehicle speed sensor signal is being transmitted by the combination meter. If there is no signal from the combination meter, despite the ECM detecting the speed signal from the speed sensor NC, the ECM interprets this as a malfunction in the speed signal circuit. The ECM then illuminates the MIL and stores the DTC.

Manual Transaxle Models

The ECM assumes that the vehicle is being driven when the fuel-cut operation* is being executed. If there is no speed signal, despite the conditions being met, the ECM interprets this as a malfunction in the speed signal circuit. The ECM then illuminates the MIL and stores the DTC.

*: Idle fuel-cut is executed when the throttle valve is fully closed and engine speed is over 2800 RPM.

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 217

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 (TP) sensor, which detects the opening angle of the throttle valve; 4) the Accelerator Pedal Position (APP) 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 218

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 idle air control at cold start. When the engine is started at an engine coolant temperature of lower than 50°C (122°F), the ECM measures the accumulated mass air flow at engine idling. If it does not reach 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).

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

HINT

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

Scheme 219

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 lower than 50°C (122°F), the ECM checks the ignition timing at 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) learning values are cleared. This DTC cannot be stored with the ISC learning values cleared.

HINT

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

Scheme 220

The battery supplies electricity to the ECM even when the ignition 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 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 or the data stored in the ECM is partly erased.

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 store the 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 standards, the ECM will illuminate the MIL and store the DTC immediately.

The ECM continuously monitors its internal processors (CPUs) and Heated Oxygen (HO2) 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, the DTC is output.

The ECM monitors the input signals of the Accelerator Pedal Position (APP) sensor No. 1. When the input signals and control signals are deviated, the DTC is output.

The ECM monitors the input signals of the Throttle Position (TP) sensor No. 1 and stop light switch. As the ECM monitors the input signals of the TP sensor No. 1 and the STP signals of the stop light switch, if the input signals and control signals are deviated, the DTC is output.

While the engine is being cranked, the 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.

*1: for M/T Models

*2: for A/T Models

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

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

DTC P0630 is stored 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 ignition switch is turned off. If the output voltage is higher than 7 V when the ignition switch is turned off, the ECM will illuminate the MIL and store the DTC when the ignition switch is turned to ON.

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

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 and the MIL comes on and the ECM stores the DTC. The vehicle must STOP (less than 3 km/h [1.86 mph]) and GO (30 km/h [18.65 mph] or more) 5 times during 2 driving cycles, in order to detect a malfunction.

P1603

After starting the engine, this DTC is stored when the engine stops without the ignition 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 run out of fuel in the past before performing troubleshooting, as this DTC is also stored when the engine stalls due to running out of fuel.

*1: for A/T Models

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 has run out of fuel in the past before performing troubleshooting, as this DTC is also stored when idling is unstable due to running out of fuel.

*1: for A/T Models

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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 and P1605 is stored FREEZE FRAME DATA P1605 ROUGH IDLING Parameter -3 -2 -1 0 1 Unit Engine Speed 644 655 374 371 337 RPM Calculate Load 23.9 24.3 29.0 30.5 33.7 % Vehicle Load 12.5 12.5 37.6 36.8 15.6 % MAF 1.95 1.95 3.34 3.26 1.28 gm/sec Atmosphere Pressure -0 -0 -0 -0 -0 psi(gauge) Coolant Temp 196 196 196 196 196 F Intake Air 120 120 120 120 120 F Battery Voltage 13.203 13.164 12.695 12.695 12.617 V Throttle Sensor Volt % 14.9 14.9 16.8 16.8 15.2 % Throttle Sensor #2 Volt % 45.8 45.8 48.2 48.2 46.2 % Throttle Sensor Position 0.0 0.0 0.0 0.0 0.0 % Throttle Motor DUTY 14.9 14.9 16.8 16.8 14.9 % Injector (Port) 2336 2359 3566 3566 3768 μs Injection Volume (Cylinder 1) 0.092 0.093 0.093 0.093 0.093 ml Fuel Pump/Speed Status ON ON ON ON ON EVAP (Purge) VSV 29.0 29.4 28.2 28.2 28.6 % EVAP Purge Flow 9.9 9.9 9.9 9.9 9.9 % Purge Density Learn Value 1.000 1.000 1.000 1.000 1.000 EVAP purge VSV OFF OFF OFF OFF OFF Target Air-Fuel Ratio 0.996 0.996 0.996 0.996 0.996 AF Lambda B1S1 0.996 0.998 1.029 1.037 1.232 AFS Voltage B1S1 3.277 3.294 3.465 3.484 4.487 V O2S B1 S2 0.835 0.835 0.835 0.835 0.835 V Short FT #1 3.906 3.906 3.125 3.125 7.812 % Long FT #1 -3.125 -3.125 -3.125 -3.125 -3.125 % Total FT #1 0.011 0.011 0.011 0.011 0.011 Fuel System Status #1 CL CL CL CL CL IGN Advance 15.0 14.5 11.0 11.0 5.5 deg Knock Feedback Value -3.0 -3.0 -3.0 -3.0 -3.0 CA Knock Correct Learn Value 18.8 18.8 18.8 18.8 18.8 CA VVT Control Status #1 ON ON ON ON ON Starter Signal Close Close Close Close Close