Engine Control System (Diagnostics & Circuit Tests): Overview Scion tC II рестайлинг

DESCRIPTION

TEXT IN ILLUSTRATION

HINT

The canister pressure sensor, the leak detection pump and the vent valve are built into the canister pump module.

TEXT IN ILLUSTRATION

Note. In the EVAP system of this vehicle, turning ON the vent valve does not seal off the EVAP system. To check for leaks in the EVAP system, disconnect the air inlet vent hose and apply pressure from atmospheric side of the canister.

While the engine is running, if a predetermined condition (closed-loop, etc.) is met, the purge VSV is opened by the ECM and fuel vapors stored in the canister are purged to the intake manifold. The ECM changes the duty cycle ratio of the purge VSV to control purge flow volume.

The purge flow volume is also determined by the intake manifold pressure. Atmospheric pressure is allowed into the canister through the vent valve to make sure that the purge flow is maintained when negative pressure (vacuum) is applied to the canister.

The following two monitors run to confirm appropriate EVAP system operation.

1. Key-off monitor This monitor checks for EVAP (evaporative emission) system leaks and canister pump module malfunctions. The monitor starts 5 hours* after the ignition switch is turned off. At least 5 hours are required for the fuel to cool down to stabilize the EVAP pressure, thus making the EVAP system monitor more accurate. The leak detection pump creates negative pressure (vacuum) in the EVAP system and the pressure is measured. Finally, the ECM monitors for leaks from the EVAP system, and malfunctions in both the canister pump module and purge VSV 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.
2. Purge flow monitor The purge flow monitor consists of the 2 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 purge 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 0.15 kPa(gauge) [1.13 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 of the purge flow monitor, is measured by the ECM. TEXT IN ILLUSTRATION *1 Canister *2 to Intake Manifold *3 ECM *4 Soak Timer *5 Purge VSV (On) *6 Fuel Tank Cap Assembly *7 Canister Filter *8 Fuel Tank *9 Leak Detection Pump (Off) *10 Canister Pressure Sensor *11 Reference Orifice (0.02 Inches) *12 Vent Valve (Off) *13 Canister Pump Module - - *a EVAP Purge Flow - - Component Operation Canister Contains activated charcoal to absorb EVAP (Evaporative Emissions) generated in fuel tank. Cut-off valve Located in fuel tank. Valve floats and closes when fuel tank is 100% full. Purge VSV (Vacuum Switching Valve) Opens or closes line between canister and intake manifold. ECM uses purge VSV to control EVAP purge flow. In order to discharge EVAP absorbed by canister to intake manifold, ECM opens purge VSV. EVAP discharge volume to intake manifold controlled by purge VSV duty cycle (current-carrying time). (Open: on, Close: off) Roll-over valve Located in fuel tank. Valve closes by its own weight when vehicle overturns to prevent fuel from spilling out. Soak timer Built into ECM. To ensure accurate EVAP monitor, measures 5 hours (+/-15 min) after ignition switch is turned off. This allows fuel to cool down, stabilizing EVAP pressure. When approximately 5 hours elapsed, ECM activates see scheme 3 Canister pump module Consists of (a) to (d) below. Canister pump module cannot be disassembled. (a) Vent valve Vents and closes EVAP system. When ECM turns valve on, EVAP system is closed. When ECM turns valve off, EVAP system is vented. Negative pressure (vacuum) is created in EVAP system to check for EVAP leaks by closing purge VSV, turning on vent valve (closing it) and operating leak detection pump see scheme 1 (b) Canister pressure sensor Indicates pressure as voltages. ECM supplies regulated 5 V to pressure sensor, and uses feedback from sensor to monitor EVAP system pressure see scheme 2 (c) Leak detection pump Creates negative pressure (vacuum) in EVAP system for leak check. (d) Reference orifice Has opening with 0.02 inch diameter. Vacuum is produced through orifice by closing purge VSV, turning off vent valve and operating leak detection pump, to monitor reference pressure. Reference pressure indicates a small leak of EVAP. TEXT IN ILLUSTRATION *1 Canister *2 Reference Orifice (0.02 Inches) *3 Canister Pressure Sensor - - *a Canister Pump Module see scheme 1 *b Airflow *c Condition: Purge Flow *d Condition: Leak Check *e Vent Valve: off (vent) *f to Canister Filter (Atmosphere) *g Leak Detection Pump: off *h Vent Valve: on (closed) *i Leak Detection Pump: on

When the ignition switch is turned to ON, the battery voltage is applied to the IGSW terminal of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil of the integration relay (EFI NO. 1 relay), closing the contacts and supplying power to terminals +B and +B2 of the ECM.

Scheme 98

When the ignition switch is turned to ON, the battery voltage is applied to the IGSW terminal of the ECM. The output signal from the MREL terminal of the ECM causes a current to flow to the coil of the integration relay (EFI NO. 1 relay), closing the contacts and supplying power to terminals +B and +B2 of the ECM.

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

Scheme 99

When the VC circuit is short-circuited, the microprocessor in the ECM and the sensors that are supplied with power through the VC circuit are inactivated because 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.

Scheme 100

Scheme 101

Scheme 102

1. CHECK MIL Check that the Malfunction Indicator Lamp (MIL) lights up when the ignition switch is turned to ON. OK MIL lights up. NG --> See step 2 OK --> See step 10
2. CHECK COMMUNICATION BETWEEN TECHSTREAM 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 11 B: Go to next step
3. CHECK MIL (THROTTLE POSITION SENSOR) Disconnect the 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 HINT: Perform "Inspection After Repair" after replacing the throttle with motor body assembly. Refer to «INITIALIZATION [05/2013 - ]»(ref-615120-S07565023022014050900000). A --> See step 12 B: Go to next step
4. CHECK MIL (ACCELERATOR PEDAL POSITION SENSOR) Disconnect the accelerator pedal position sensor connector. Turn the ignition switch to ON. Check the MIL. RESULT Result Proceed to MIL illuminates A MIL does not illuminate B A --> See step 13 B: Go to next step
5. CHECK MIL (CANISTER PUMP MODULE) Disconnect the 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 A --> See step 14 B: Go to next step
6. CHECK MIL (INTAKE AIR CONTROL VALVE ACTUATOR (FOR TCV)) Disconnect the intake air control valve actuator (for TCV) connector. Turn the ignition switch to ON. Check the MIL. RESULT Result Proceed to MIL illuminates A MIL does not illuminate B A --> See step 16 B: Go to next step
7. CHECK MIL (CAMSHAFT POSITION SENSOR (FOR INTAKE SIDE)) Disconnect the camshaft position sensor (for Intake Side) connector. Turn the ignition switch to ON. Check the MIL. RESULT Result Proceed to MIL illuminates A MIL does not illuminate B A --> See step 17 B: Go to next step
8. CHECK MIL (CAMSHAFT POSITION SENSOR (FOR EXHAUST SIDE)) Disconnect the camshaft position sensor (for Exhaust Side) connector. Turn the ignition switch to ON. Check the MIL. RESULT Result Proceed to MIL illuminates A MIL does not illuminate B A --> See step 18 B: Go to next step
9. CHECK HARNESS AND CONNECTOR Disconnect the throttle with motor body assembly connector. Disconnect the accelerator pedal position sensor connector. Disconnect the canister pump module connector. Disconnect the intake air control valve actuator (for TCV) connector. Disconnect the camshaft position sensor (for Intake Side) connector. Disconnect the camshaft position sensor (for Exhaust Side) connector. Disconnect the ECM connectors. Measure the resistance according to the value(s) in the table below. Standard Resistance Tester Connection Condition Specified Condition B30-88 (VCTA) - Body ground Always 10 kohms or higher A35-57 (VCPA) - Body ground Always 10 kohms or higher A35-58 (VCP2) - Body ground Always 10 kohms or higher B30-72 (VCIA) - Body ground Always 10 kohms or higher B30-113 (VCPP) - Body ground Always 10 kohms or higher B30-98 (VCE1) - Body ground Always 10 kohms or higher B30-99 (VCV1) - Body ground Always 10 kohms or higher NG --> REPAIR OR REPLACE HARNESS OR CONNECTOR OK --> See step 15
10. PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to «PROBLEM SYMPTOMS TABLE [05/2013 - 01/2014]»(ref-615120-S16624443392014050900000)
11. GO TO MIL CIRCUIT. Refer to «MIL Circuit»(ref-615235-S24980826702014050900000)
12. REPLACE THROTTLE WITH MOTOR BODY ASSEMBLY. Refer to «REMOVAL [05/2013 - ]»(ref-615228-S19667413492014050900000)
13. REPLACE ACCELERATOR PEDAL POSITION SENSOR ASSEMBLY. Refer to «REMOVAL [05/2013 - ]»(ref-615228-S21579820712014050900000)
14. REPLACE CANISTER. Refer to «REMOVAL [05/2013 - ]»(ref-615251-S01365067382014050900000)
15. REPLACE ECM. Refer to «REMOVAL [05/2013 - 01/2014]»(ref-615228-S17169059992014050900000)
16. REPLACE INTAKE AIR CONTROL VALVE ACTUATOR (FOR TCV). Refer to «REMOVAL [05/2013 - ]»(ref-615249-S21260711612014050900000)
17. REPLACE CAMSHAFT POSITION SENSOR. Refer to «REMOVAL [05/2013 - ]»(ref-615228-S31093354652014050900000)
18. REPLACE CAMSHAFT POSITION SENSOR. Refer to «REMOVAL [05/2013 - ]»(ref-615228-S31093354652014050900000)

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

When the VC circuit is short-circuited, the microprocessor in the ECM and the sensors that are supplied with power through the VC circuit are inactivated because 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.

When the engine is cranked, the starter relay drive signal output from the ignition switch*1 or power source control ECU*2 is input into the STA terminal of the ECM, and the NE signal generated by the crankshaft position sensor is input into the NE+ terminal. The ECM determines that the engine is cranked, and turns transistor Tr1 in the ECM internal circuit on. Current flows to the C/OPN (Circuit Opening) relay by turning Tr1 on.

Then, the fuel pump operates.

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

*1: w/o Smart Key System

*2: w/ Smart Key System

Scheme 103

When the engine is cranked, the starter relay drive signal output from the ignition switch*1 or power source control ECU*2 is input into the STA terminal of the ECM, and the NE signal generated by the crankshaft position sensor is input into the NE+ terminal. The ECM determines that the engine is cranked, and turns transistor Tr1 in the ECM internal circuit on. Current flows to the C/OPN (Circuit Opening) relay by turning Tr1 on.

Then, the fuel pump operates.

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

*1: w/o Smart Key System

*2: w/ Smart Key System

The fuel injectors are located on the intake manifold. They inject fuel into the cylinders based on the signals from the ECM.

Scheme 104

The fuel injectors are located on the intake manifold. They inject fuel into the cylinders based on the signals from the ECM.

While the engine is being cranked, current flows from terminal ST1 of the ignition switch*1 or terminal STAR of the power source control ECU*2 to the park/neutral position switch (for A/T) or clutch pedal switch (for M/T) and also flows to terminal STA of the ECM (STA signal).

1. *1: w/o Smart Key System
2. *2: w/ Smart Key System

Scheme 105

Scheme 106

While the engine is being cranked, current flows from terminal ST1 of the ignition switch*1 or terminal STAR of the power source control ECU*2 to the park/neutral position switch (for A/T) or clutch pedal switch (for M/T) and also flows to terminal STA of the ECM (STA signal).

1. *1: w/o Smart Key System
2. *2: w/ Smart Key System

This circuit opens and closes the Intake Air Control Valve (IACV) according to the engine load in order to increase intake efficiency (ACIS: Acoustic Control Induction System).

Scheme 107

Scheme 108

This circuit opens and closes the Intake Air Control Valve (IACV) according to the engine load in order to increase intake efficiency (ACIS: Acoustic Control Induction System).

When the vehicle is being driven, depressing the accelerator pedal sensor assembly and brake 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 109

Activation Conditions

1. When the accelerator pedal and brake pedal are depressed.

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

Items Controlled

1. When the vehicle speed is extremely low, the accelerator opening value used when controlling the engine is reduced more than normal.

HINT

During control, the Accelerator Position value in the Data List becomes smaller.

1. When the vehicle speed is not extremely low, the accelerator opening value is forcibly lowered to a fixed value.

HINT

During control, the Accelerator Position value in the Data List is forcibly reduced to a specified value regardless of the actual accelerator opening value (Accel Sens.No. 1 Volt%).

Deactivation Conditions

1. When the brake pedal or the accelerator pedal returns to some degree.

When the vehicle is being driven, depressing the accelerator pedal sensor assembly and brake 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.

Activation Conditions

1. When the accelerator pedal and brake pedal are depressed.

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

Items Controlled

1. When the vehicle speed is extremely low, the accelerator opening value used when controlling the engine is reduced more than normal.

HINT

During control, the Accelerator Position value in the Data List becomes smaller.

1. When the vehicle speed is not extremely low, the accelerator opening value is forcibly lowered to a fixed value.

HINT

During control, the Accelerator Position value in the Data List is forcibly reduced to a specified value regardless of the actual accelerator opening value (Accel Sens.No. 1 Volt%).

Deactivation Conditions

1. When the brake pedal or the accelerator pedal returns to some degree.

The MIL (Malfunction Indicator Lamp) is used to indicate the detection of vehicle malfunctions 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 when the engine is started. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the Techstream.

Scheme 110

The MIL (Malfunction Indicator Lamp) is used to indicate the detection of vehicle malfunctions 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 when the engine is started. If the MIL remains illuminated or is not illuminated, conduct the following troubleshooting procedure using the Techstream.

See also:
• DTC P2420: Evaporative Emission System Switching Valve Control Circuit High
• ON-VEHICLE INSPECTION [05/2013 - ] - Step 1