Engine Control System (Sedan) (Diagnostic Codes (P1604-2A00) & Circuit Tests): Overview Toyota Yaris III

DESCRIPTION

This DTC is stored when the engine does not start even though the STA signal is input or when the engine takes a long time to start, and when the engine speed is low or the engine stalls just after the engine starts.

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 there is engine starting trouble due to running out of fuel.

*1: for Automatic Transaxle Models

*2: for Manual Transaxle 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 air induction system during starting difficulty FREEZE FRAME DATA P1604 STARTABILITY MALFUNCTION Parameter -3 -2 -1 0 1 Unit Engine Speed 1497 794 334 249 249 RPM Calculate Load 34.5 28.2 32.1 87.8 87.4 % Vehicle Load 8.6 21.9 15.6 7.4 5.8 % MAF 1.70 2.31 0.70 0.25 0.20 gm/sec Atmosphere Pressure -1 -1 -1 -1 -1 psi(gauge) Coolant Temp 167 167 167 167 167 F Intake Air 93 93 93 93 93 F Ambient Temperature 66 66 66 66 66 F Battery Voltage 13.2 13.0 12.3 12.3 12.3 V Throttle Sensor Volt % 16.0 17.6 17.2 15.6 15.6 % Throttle Sensor #2 Volt % 48.2 50.1 49.4 47.8 47.8 % Throttle Sensor Position 0.0 0.0 0.0 0.0 0.0 % Throttle Motor DUTY 16.0 17.6 17.6 15.6 15.6 % Injector (Port) 3204 2562 2562 2562 2562 μs Injection Volume (Cylinder 1) 0.152 0.152 0.152 0.152 0.152 ml Fuel Pump/Speed Status ON ON ON ON ON EVAP (Purge) VSV 0.0 0.0 0.0 0.0 0.0 % Evap Purge Flow 0.0 0.0 0.0 0.0 0.0 % Purge Density Learn Value 0.000 0.000 0.000 0.000 0.000 EVAP Purge VSV OFF OFF OFF OFF OFF Target Air-Fuel Ratio 0.830 0.841 0.871 0.799 0.799 AF Lambda B1 S1 1.014 1.016 1.021 1.022 1.027 AFS Voltage B1 S1 3.37 3.38 3.40 3.41 3.42 V O2S B1 S2 0.82 0.31 0.07 0.05 0.03 V Short FT #1 0.000 0.000 0.000 0.000 0.000 % Long FT #1 0.000 -4.069 -4.737 -4.737 -4.737 % Total FT #1 -0.043 -0.043 -0.043 -0.043 -0.043 Fuel System Status #1 OL OL OL OL OL IGN Advance -4.0 2.0 4.0 0.0 0.0 deg Knock Feedback Value -3.0 -3.0 -3.0 -3.0 -3.0 CA Knock Correct Learn Value 14.0 14.0 14.0 14.0 14.0 CA VVT Control Status #1 OFF OFF OFF OFF OFF Starter Signal Close Close Close Close Close

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 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 with motor body assembly. 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.

MONITOR DESCRIPTION

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 stores a DTC.

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 stores a DTC.

If the malfunction is not repaired successfully, a DTC is stored when the engine is quickly revved to a high RPM several times after the engine has idled for 5 seconds after engine start.

The idling speed is controlled by the Electronic Throttle Control System (ETCS).

The ETCS is comprised of a throttle actuator, which operates the throttle valve, and a throttle position sensor, which detects the opening amount of the throttle valve.

The ECM controls the throttle actuator to adjust the throttle valve opening amount so that the idling speed is maintained at the target idling speed.

HINT

1. The ISC learned value is the calculated intake air amount corresponding to the throttle opening amount necessary to maintain the idling speed.
2. This malfunction is only detected once per trip. After it has been detected once, the system will not monitor for the malfunction for the rest of the trip.
3. The system uses the throttle with motor body assembly and mass air flow meter assembly to detect this malfunction.

If there are deposits in the throttle valve, a decrease in the ISC flow rate may cause engine stall and unstable idling. Therefore, the necessary ISC flow rate for idling is maintained using the ISC learned value and feedback. The ECM stores this DTC if the ISC learned value approaches its limit. The ECM begins monitoring for the DTC detection conditions when the following preconditions are met: 1) the mass air flow meter is normal: 2) atmospheric pressure is 85 kPa (638 mmHg) or higher: 3) the vehicle has been driven at a speed of 30 km/h (18.65 mph) or more at least once: and 4) the engine coolant temperature is 45 °C (113 °F) or less at engine start, the engine is warmed up and conditions for ISC learning are met, or the ignition switch has been turned to ON (include engine running) for 1 hour or more, the engine is warmed up and conditions for ISC learning are met.

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 with motor body assembly. The TP sensor provides feedback to the ECM in order that it can control the throttle actuator, and therefore the throttle valve, appropriately in response 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 stores a DTC.

If the malfunction is not repaired successfully, a DTC is stored 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. The voltage (+BM) is monitored and when it 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 ignition 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.

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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 stores the DTC.

If the malfunction is not repaired successfully, the DTC is stored 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 stores the DTC.

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

HINT

1. These DTCs relate to the Accelerator Pedal Position (APP) sensor.
2. This ETCS (Electronic Throttle Control System) does not use a throttle cable.

The 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.

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HINT

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

HINT

Accelerator pedal positions are expressed as voltages.

When either output voltage 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 stores 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 stored.

If the malfunction is not repaired successfully, a DTC is stored 2 seconds after the engine is next started.

HINT

1. This DTC relates to the accelerator pedal position sensor.
2. Refer to DTC P2120. Refer to «DESCRIPTION»(ref-472647-S11165574432012051500000).

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

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.

The A/F sensor generates a 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 of 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 air-fuel ratio detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte through the alumina, and therefore the sensor activation is accelerated.

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a 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 into a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.

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HINT

1. When either of these DTCs is stored, check the A/F sensor output by entering the following menus on a Techstream: Powertrain / Engine and ECT / Data List / AFS Voltage B1S1.
2. Short-term fuel trim values can also be read using the Techstream.
3. The ECM regulates the voltages at the A1A+ and A1A- terminals of the ECM to a constant level. Therefore, the A/F sensor output voltage cannot be confirmed without using the Techstream.
4. If the A/F sensor is malfunctioning, the ECM stores the DTC P2195 or P2196.

Sensor voltage detection monitor

Under the air-fuel ratio feedback control, if the A/F sensor output voltage 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 stores a DTC.

Example

If the A/F sensor output voltage is less than 2.8 V (very rich condition) for 10 seconds, despite the rear HO2 sensor output voltage being less than 0.6 V, the ECM stores DTC P2196. Alternatively, if the A/F sensor output voltage is more than 3.8 V (very lean condition) for 10 seconds, despite the rear HO2 sensor output voltage being 0.15 V or more, DTC P2195 is stored.

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 3 seconds or more of cumulative time, the ECM interprets this as a malfunction in the A/F sensor and stores DTC P2195 (high-side stuck). If the A/F sensor output is less than 1.0 mA for 3 seconds or more of cumulative time, the ECM stores DTC P2196 (low-side stuck).

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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.

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

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

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

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

The description can be found in 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 (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 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.

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TEXT IN ILLUSTRATION

P2420: Vent valve stuck open (vent)

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

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The soak timer operates after the ignition switch is turned off. When a certain amount of time has elapsed after turning the ignition switch off the soak timer activates the ECM to perform malfunction checks which can only be performed after the engine is stopped. The soak timer is built into the ECM.

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1. 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 stores the DTC.
2. If the soak timer activates the ECM even though only a short amount of time has elapsed since the ignition switch was turned off, or if the soak timer does not activate the ECM even though a considerable amount of time has elapsed since the ignition switch was turned off, the ECM determines that the soak timer is malfunctioning, illuminates the MIL and stores a DTC the next time the ignition switch is turned ON.

HINT

Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.

Refer to DTC P2195. Refer to DESCRIPTION.

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 control is performed for approximately 10 seconds after the preconditions are met in order to measure the A/F sensor response rate. During active A/F 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 control and uses it to calculate the A/F sensor response rate deterioration level.

If the A/F sensor response rate deterioration level is less than the threshold, the ECM interprets this as a malfunction and stores the DTC.

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When the ignition switch is turned to ON, the battery voltage is applied to the IGSW of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil, closing the contacts of the integration relay (EFI relay) and supplying power to terminals +B and +B2 of the ECM.

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1. INSPECT INTEGRATION NO. 1 RELAY (POWER SOURCE OF INTEGRATION RELAY) Remove the integration relay from the engine room relay block. Measure the voltage between the terminal of the integration relay and body ground. Standard voltage Tester Connections Specified Conditions Engine room relay block (1C-1) - Body ground 11 to 14 V Reinstall the integration relay. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - INTEGRATION RELAY) OK: Go to next step
2. INSPECT INTEGRATION NO. 1 RELAY (EFI RELAY AND IG2 RELAY) Remove the integration relay from the engine room relay block. Inspect the EFI fuse and the AM2 fuse. Remove the EFI fuse and AM2 fuse from the integration relay. Check the resistance of the EFI fuse and AM2 fuse. Standard resistance Below 1 ohms Reinstall the EFI fuse and the AM2 fuse. Inspect the EFI relay and the IG2 relay. Check the resistance between the terminals shown below. Standard resistance Tester Connections Specified Conditions 1C-1 - 1A-4 10 kohms or higher Below 1 ohms (when battery voltage is applied to terminals 1A-2 and 1A-3) 1C-1 - 1B-4 10 kohms or higher Below 1 ohms (when battery voltage is applied to terminals 1B-2 and 1B-3) 1C-1 - 1B-1 Below 1 ohms Reinstall the integration relay. NG --> REPLACE INTEGRATION NO. 1 RELAY OK: Go to next step
3. CHECK HARNESS AND CONNECTOR (+B, +B2 AND MREL CIRCUIT) Check the harness and the connectors between the integration relay and the ECM. Remove the integration relay from the engine room relay block. Disconnect the A21 ECM connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions MREL (A21-44) - Engine room relay block (1A-2) Below 1 ohms +B (A21-2) - Engine room relay block (1A-4) +B2 (A21-1) - Engine room relay block (1A-4) Standard resistance (Check for short) Tester Connections Specified Conditions MREL (A21-44) or Engine room relay block (1A-2) - Body ground 10 kohms or higher +B (A21-2) or Engine room relay block (1A-4) - Body ground +B2 (A21-1) or Engine room relay block (1A-4) - Body ground Check the harness and the connector between the integration relay and body ground. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions Engine room relay block (1A-3) - Body ground Below 1 ohms Reinstall the integration relay. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
4. CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND) Disconnect the C20 ECM connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions E1 (C20-104) - Body ground Below 1 ohms Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
5. INSPECT ECM (IGSW VOLTAGE) Disconnect the C20 and A21 ECM connectors. Turn the ignition switch to ON. Measure the voltage between the terminals of the C20 and A21 ECM connectors. Standard voltage Tester Connections Specified Conditions IGSW (A21-28) - E1 (C20-104) 11 to 14 V Reconnect the ECM connectors. NG --> See step 6 OK --> See step 10
6. INSPECT FUSE (IGN FUSE) Remove the IGN fuse from the main body ECU. Check the IGN fuse resistance. Standard resistance Below 1 ohms Reinstall the IGN fuse. NG --> CHECK FOR SHORTS IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE OK: Go to next step
7. CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY - ECM) Remove the integration relay from the engine room relay block. Disconnect the A21 ECM connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions Engine room relay block (1B-4) - IGSW (A21-28) Below 1 ohms Standard resistance (Check for short) Tester Connections Specified Conditions Engine room relay block (1B-4) or IGSW (A21-28) - Body ground 10 kohms or higher Reinstall the integration relay. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
8. CHECK HARNESS AND CONNECTOR (INTEGRATION RELAY - IGNITION SWITCH) Check the harness and the connectors between the integration relay and the ignition switch. Remove the integration relay from the engine room relay block. Disconnect the D8 ignition switch connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions Engine room relay block (1B-2) - IG2 (D8-6) Below 1 ohms Standard resistance (Check for short) Tester Connections Specified Conditions Engine room relay block (1B-2) or IG2 (D8-6) - Body ground 10 kohms or higher Check the harness and the connectors between the integration relay and body ground. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions Engine room relay block (1B-3) - Body ground Below 1 ohms Reinstall the integration relay. Reconnect the ignition switch connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK: Go to next step
9. INSPECT IGNITION SWITCH Disconnect the D8 ignition switch connector. Check the resistance between the terminals shown below. Standard resistance Tester Connections Key Positions Specified Conditions - LOCK 10 kohms or higher 2-4 ACC Below 1 ohms 1-2-4 ON 5-6 1-3-4 START 5-6-7 Reconnect the ignition switch connector. NG --> REPLACE IGNITION SWITCH OK --> REPAIR OR REPLACE HARNESS OR CONNECTOR (IGNITION SWITCH - INTEGRATION RELAY)
10. REPLACE ECM. Refer to «REMOVAL»(ref-472637-S09325593862012051500000)

The ECM constantly generates 5 V power 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.

Scheme 223

When the VC circuit is short-circuited, the microprocessor in the ECM and sensors that are supplied with 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 ignition switch is first turned to ON. The MIL goes off when the engine is started.

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1. CHECK MIL Check that Malfunction Indicator Lamp (MIL) lights up when turning the ignition switch ON. OK MIL lights up NG --> See step 2 OK --> See step 7
2. CHECK COMMUNICATION BETWEEN TESTER AND ECM Connect the Techstream to the DLC3. Turn the ignition switch to ON. Turn the Techstream on. Check the communication between the Techstream and ECM. RESULT Result Proceed To Communication is possible A Communication is not possible B A --> See step 8 B: Go to next step
3. CHECK MIL (THROTTLE POSITION SENSOR) Disconnect the C17 throttle with motor body assembly connector. Turn the ignition switch to ON. Check the MIL. RESULT Result Proceed To MIL illuminates A MIL does not illuminate B Reconnect the throttle with motor body assembly connector. A --> See step 9 B: Go to next step
4. CHECK MIL (ACCELERATOR PEDAL POSITION SENSOR) Disconnect the A20 accelerator pedal assembly connector. Turn the ignition switch to ON. Check the MIL. RESULT Result Proceed To MIL illuminates A MIL does not illuminate B Reconnect the accelerator pedal assembly connector. A --> See step 10 B: Go to next step
5. CHECK MIL (CANISTER PUMP MODULE) Disconnect the J25 canister pump module connector. Turn the ignition switch to ON. Check the MIL. RESULT Result Proceed To MIL illuminates A MIL does not illuminate B Reconnect the canister pump module connector. A --> See step 11 B: Go to next step
6. CHECK HARNESS AND CONNECTOR (ECM - EACH SENSOR) Disconnect the C17 throttle with motor body assembly connector. Disconnect the A20 accelerator pedal assembly connector. Disconnect the J25 canister pump module connector. Disconnect the A21 and C20 ECM connectors. Check the resistance. Standard resistance (Check for short) Tester Connections Specified Conditions VCTA (C20-67) - Body ground 10 kohms or higher VCPA (A21-57) - Body ground VCP2 (A21-58) - Body ground VCPP (C20-70) - Body ground Reconnect the throttle with motor body assembly connector. Reconnect the accelerator pedal assembly connector. Reconnect the canister pump module connector. Reconnect the ECM connectors. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 12
7. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE»(ref-472422-S06319120112012051500000)
8. GO TO MIL CIRCUIT. Refer to «MIL Circuit»(ref-472647-S39677999762012051500000)
9. REPLACE THROTTLE WITH MOTOR BODY ASSEMBLY. Refer to «REMOVAL»(ref-472637-S42179391792012051500000)
10. REPLACE ACCELERATOR PEDAL ASSEMBLY. Refer to «REMOVAL»(ref-472637-S21969896962012051500000)
11. REPLACE CANISTER. Refer to «REMOVAL»(ref-472640-S39338606712012051500000)
12. REPLACE ECM. Refer to «REMOVAL»(ref-472637-S09325593862012051500000)

When the engine is cranked, the starter relay drive signal output from the STAR terminal of the ECM is input into the STA terminal of the ECM, and NE signal generated by the crankshaft position sensor is also input into the NE+ terminal. Thus, the ECM interprets that the engine is cranked, and turns the transistor Tr1 in the ECM internal circuit ON. The current flows to the C/OPN (Circuit Opening) relay by turning the Tr1 ON. Then, the fuel pump operates.

While the NE signal is input into the ECM, when engine is running, the ECM turns the Tr1 on continuously.

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The fuel injector assembly inject fuel based on the signals from the ECM.

Scheme 229

The cranking holding control system provides a current to the starter when the ECM detects the ignition switch's start signal (STSW). When the ECM judges that the engine has started, the system cuts the current to the starter. When the ECM receives the STSW signal, it turns on the ACC (Accessory) relay, which prevents flickering of the combination meter, clock and audio system. Also, the ECM sends a signal to the ECM's STAR terminal. Then the STAR output signal travels through the Park/Neutral Position (PNP) switch to the ST relay, causing the starter to activate. When the engine is cranking, the starter operation signal is sent to the ECM's STA terminal.

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1. READ VALUE USING TECHSTREAM (STARTER SIGNAL) Connect the Techstream to the DLC3. Turn the ignition switch to ON and turn the Techstream on. Turn the Techstream on. Enter the following menus: Powertrain / Engine and ECT / Engine and ECT / Starter Signal. Check the result when the ignition switch is turned to ON and START. OK Ignition Switch Position Starter Signal ON Close (Starter signal OFF) START Open (Starter signal ON) RESULT Result Proceed to NG A OK B B --> See step 12 A: Go to next step
2. INSPECT ECM (STSW VOLTAGE) Disconnect the A21 ECM connector. Measure the voltage between the terminals of the ECM connector and body ground while cranking the engine. Standard voltage Tester Connections Specified Conditions STSW (A21-14) - Body ground 11 to 14 V Result Result Proceed to Within standard range(A/T) A Within standard range (M/T) B Outside standard range C Reconnect the ECM connector. B --> See step 6 C --> See step 9 A: Go to next step
3. INSPECT ECM (STAR VOLTAGE) Disconnect the C27 Park/Neutral Position (PNP) switch connector. Measure the voltage between the terminals of the PNP switch connector and body ground while cranking the engine. Standard voltage Tester Connections Specified Conditions B (C27-4) - Body ground 11 to 14 V Reconnect the PNP switch connector. NG --> See step 10 OK: Go to next step
4. INSPECT PARK/NEUTRAL POSITION SWITCH Disconnect the C27 PNP switch connector. Check the resistance between each terminal shown below when the shift lever is moved to each range. Standard resistance Tester Connections Shift Position Specified Conditions PL (6) - RB (2) P Below 1 ohms L (5) - B (4) RL (1) - RB (2) R NL (9) - RB (2) N L (5) - B (4) DL (7) - RB (2) D 2L (3) - RB (2) 2 LL (8) - RB (2) L Reconnect the PNP switch connector. NG --> See step 15 OK: Go to next step
5. CHECK HARNESS AND CONNECTOR (PARK/NEUTRAL POSITION SWITCH - ECM) Disconnect the C27 PNP switch connector. Disconnect the A21 ECM connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions L (C27-5) - STA (A21-48) Below 1 ohms Standard resistance (Check for short) Tester Connections Specified Conditions L (C27-5) or STA (A21-48) - Body ground 10 kohms or higher Reconnect the PNP switch connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 16
6. INSPECT ECM (STAR VOLTAGE) Disconnect the A16 clutch start switch connector. Measure the voltage between the terminals of the clutch start switch connector and body ground while cranking the engine. Standard voltage Tester Connections Specified Conditions B (A16-2) - Body ground 11 to 14 V Reconnect the clutch start switch connector. NG --> See step 11 OK: Go to next step
7. INSPECT CLUTCH START SWITCH Disconnect the A16 clutch start switch connector. Check the resistance between the terminals of the clutch start switch. Standard resistance Switch Positions Specified Conditions Pushed in Below 1 ohms Released 10 kohms or higher Reconnect the clutch start switch connector. NG --> See step 17 OK: Go to next step
8. CHECK HARNESS AND CONNECTOR (CLUTCH START SWITCH - ECM) Disconnect the A16 clutch start switch connector. Disconnect the A21 ECM connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions L (A16-1) - STA (A21-48) Below 1 ohms Standard resistance (Check for short) Tester Connections Specified Conditions L (A16-1) or STA (A21-48) - Body ground 10 kohms or higher Reconnect the clutch start switch connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 18
9. INSPECT IGNITION SWITCH Disconnect the D8 ignition switch connector. Check the resistance between the terminals shown below. Standard resistance Key Positions Tester Connections Specified Conditions LOCK - 10 kohms or higher ACC 2 - 4 Below 1 ohms ON 1 - 2 - 4 5 - 6 START 1 - 3 - 4 5 - 6 - 7 Reconnect the ignition switch connector. NG --> See step 19 OK --> REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - IGNITION SWITCH - BATTERY)
10. CHECK HARNESS AND CONNECTOR (IGNITION SWITCH - PARK/NEUTRAL POSITION SWITCH - ECM) Disconnect the D8 ignition switch connector. Disconnect the C27 PNP switch connector. Disconnect the C20 ECM connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions ST2 (D8-7) - B (C27-4) Below 1 ohms STAR (C20-52) - B (C27-4) STAR (C20-52) - L (C27-5) Standard resistance (Check for short) Tester Connections Specified Conditions ST2 (D8-7) or B (C27-4) - Body ground 10 kohms or higher STAR (C20-52) or B (C27-4) - Body ground STAR (C20-52) or L (C27-5) - Body ground Reconnect the ignition switch connector. Reconnect the PNP switch connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 20
11. CHECK HARNESS AND CONNECTOR (IGNITION SWITCH - CLUTCH START SWITCH - ECM) Disconnect the D8 ignition switch connector. Disconnect the A16 clutch start switch connector. Disconnect the C20 ECM connector. Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions ST2 (D8-7) - B (A16-2) Below 1 ohms STAR (C20-52) - B (A16-2) STAR (C20-52) - L (A16-1) Standard resistance (Check for short) Tester Connections Specified Conditions ST2 (D8-7) or B (A16-2) - Body ground 10 kohms or higher STAR (C20-52) or B (A16-2) - Body ground STAR (C20-52) or L (A16-1) - Body ground Reconnect the ignition switch connector. Reconnect the clutch start switch connector. Reconnect the ECM connector. NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 21
12. INSPECT BATTERY Check that the battery is not depleted. Refer to «ON-VEHICLE INSPECTION»(/toyota/yaris/iii-2010-2014/remont/charging-system/#charging-system-sedan-inspection__on-vehicle-inspection) . OK Battery is not depleted. NG --> REPLACE BATTERY OK: Go to next step
13. CHECK BATTERY TERMINAL Check that the battery terminals are not loose or corroded. OK Battery terminals are not loose or corroded. NG --> REPAIR OR REPLACE BATTERY TERMINAL OK: Go to next step
14. CHECK HARNESS AND CONNECTOR (PNP SWITCH OR CLUTCH START SWITCH - ST RELAY) Remove the ST relay from the engine room relay block. Disconnect the C27 PNP switch connector (A/T). Disconnect the A16 clutch start switch connector (M/T). Check the resistance. Standard resistance (Check for open) Tester Connections Specified Conditions L (C27-5) - ST relay (2) Below 1 ohms L (A16-1) - ST relay (2) ST relay (1) - Body ground Standard resistance (Check for short) Tester Connections Specified Conditions L (C27-5) or ST relay (2) - Body ground 10 kohms or higher L (A16-1) or ST relay (2) - Body ground Reinstall the ST relay. Reconnect the PNP switch connector (A/T). Reconnect the clutch start switch connector (M/T). NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> CHECK AND REPLACE STARTER RELAY AND STARTER
15. REPLACE PARK / NEUTRAL POSITION SWITCH. Refer to «REMOVAL»(ref-472644-S22282739222012051500000)
16. REPLACE ECM. Refer to «REMOVAL»(ref-472637-S09325593862012051500000)
17. REPLACE CLUTCH START SWITCH. Refer to «REMOVAL»(ref-472653-S31310627772012051500000)
18. REPLACE ECM. Refer to «REMOVAL»(ref-472637-S09325593862012051500000)
19. REPLACE IGNITION SWITCH. Refer to «REMOVAL»(ref-472652-S15831384822012051500000)
20. REPLACE ECM. Refer to «REMOVAL»(ref-472637-S09325593862012051500000)
21. REPLACE ECM. Refer to «REMOVAL»(ref-472637-S09325593862012051500000)

When the vehicle is being driven with the accelerator pedal depressed, depressing the brake pedal without releasing the accelerator pedal will activate the brake override system to restrict driving torque. The conditions for activating the brake override system as well as the items that are controlled are explained below.

Scheme 243

Activation Conditions

1. Vehicle is running at or above the specified speed.
2. The accelerator pedal is depressed beyond a specified level, and then the brake pedal is depressed.

Note. The vehicle may not enter the brake override system control due to the relation of the accelerator pedal angle and the vehicle's speed.

Items Controlled

1. Driving torque is restricted.

HINT

During brake override system control, the value for the accelerator pedal angle (which is used for engine control) is forcibly reduced to a specified value. For this reason, the Data List value for Accelerator Position (applied to electronic throttle control) will be replaced with a specified value regardless of the actual accelerator pedal angle (Accel Sens. No. 1 Volt %, Accel Sens. No. 2 Volt %)

Deactivation Conditions

1. When the Stop Light Switch turns OFF or the actual accelerator pedal angle increases or decreases beyond the specified range.

The MIL (Malfunction Indicator Lamp) is used to indicate vehicle malfunction detections by the ECM. When the ignition switch is turned to ON, 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 ignition switch is first turned to ON, 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 a Techstream.

Scheme 244

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