Engine Controls - Theory & Operation: Other Toyota 4Runner III

ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS)

Note. ETCS may also be referred to as Electronic Throttle Control System-Intelligent (ETCS-I or ETCS-i).

Land Cruiser

ETCS consists of throttle body, accelerator pedal position sensor, Throttle Position (TP) sensor, throttle control motor, magnetic clutch and Engine Control Module (ECM). ETCS uses the ECM to calculate throttle valve opening in the throttle body in relation to driving conditions. ETCS controls idle speed control system and cruise control system operation. Accelerator pedal position sensor is mounted on throttle body and is integrated with throttle lever which attaches to the throttle cable. (Scheme 1) Accelerator pedal position sensor converts amount of accelerator pedal position into 2 different types of output signals and delivers input signals to the ECM. TP sensor delivers input signals to ECM to indicated throttle valve opening.

ECM uses these input signals to operate throttle control motor to obtain proper operating speeds in relation to accelerator pedal position and engine speed, obtain proper idle speed, and provide cruise control operation. Throttle control motor is mounted on side of throttle body and operates throttle valve on throttle body by use of a magnetic clutch.

In the event of a ETCS malfunction, Malfunction Indicator Light (MIL) on instrument panel will be illuminated and Diagnostic Trouble Code (DTC) will be stored in ECM. If malfunction exists, magnetic clutch will be disengaged, allowing spring pressure to close the throttle valve. When magnetic clutch is disengaged, throttle control motor will not operate the throttle valve. If ETCS is shut off, accelerator pedal may be used to operate throttle valve for vehicle operation in limp mode by using limp mode lever on throttle body to operate the throttle valve. (Scheme 1)

Scheme 1

INTAKE AIR CONTROL VALVE SYSTEM

Note. Intake air control valve system may also be referred to as Acoustic Control Induction System (ACIS).

Avalon, Camry 3.0L V6, Camry Solara 3.0L V6 & Sienna

Engine Control Module (ECM) controls amount of airflow into intake manifold by use of an intake air control valve. Intake air control valve is located at end of air intake chamber. (Scheme 2) Operation of intake air control valve system provides increased power in all speed ranges. ECM uses an engine RPM input signal and throttle position sensor input signal for determining intake air control valve system operation. Engine RPM input signal is provided by camshaft and crankshaft position sensors.

ECM controls ground circuit for intake air control valve system Vacuum Switching Valve (VSV). The VSV controls vacuum supply from vacuum tank to the actuator, which operates intake air control valve in air intake chamber.

Scheme 2

ENGINE CONTROL SYSTEM

Engine control system is a computerized emission, ignition and fuel injection control system. Engine control system lowers exhaust emissions while maintaining good fuel economy and driveability. Engine control system consists of various sensors, switches and control units. (Scheme 3)- (Scheme 14). The Engine Control Module (ECM) controls engine control system based on input signals received from various input devices. ECM contains preprogrammed data to maintain optimum engine performance under all operating conditions.

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Avalon, Camry, Camry Solara, Land Cruiser, Sienna & 4Runner

Engine immobilizer system is a theft deterrent system that disables engine from starting by not allowing fuel injector operation and ignition system operation unless ignition key identification code matches ignition key identification code stored in Engine Control Module (ECM). Engine immobilizer system may be standard feature or optional feature on specified models. See ENGINE IMMOBILIZER SYSTEM AVAILABILITY table.

Engine immobilizer system consists of ignition key with transponder chip, transponder key coil, transponder key amplifier and ECM. Transponder chip is incorporated into ignition key. When ignition key is inserted into ignition lock cylinder, the ECM instructs transponder key coil on ignition lock cylinder to supply an electromagnetic energy that enables transponder chip to transmit an ignition key identification code signal.

Transponder key amplifier then amplifies ignition key identification code signal and delivers ignition key identification code signal to the ECM. ECM compares received ignition key identification code signal to ignition key identification code stored in the ECM. If ignition key identification code signal and ignition key identification code in the ECM match, ECM will allow fuel injector operation and ignition system operation. If ignition key identification code signal and ignition key identification code in the ECM do not match, ECM will not allow fuel injector operation and ignition system operation. For additional information on system operation and testing, see appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT.

ENGINE IMMOBILIZER SYSTEM AVAILABILITY

ENGINE CONTROL MODULE (ECM)

ECM monitors and controls vehicle emissions, fuel system, ignition system and other various systems by using input signals from various input devices. ECM processes input signals from input devices and delivers output signals to various components for controlling system operation to achieve optimum engine performance for all operating conditions. See INPUT DEVICES and OUTPUT SIGNALS . ECM contains a fail-safe function which is used in case of sensor or switch failure. Fail-safe function uses preprogrammed values to provide a limp-in mode for minimal driveability. If a failure exists, ECM will inform the driver by turning on Malfunction Indicator Light (MIL) on the instrument panel.

Note. MIL may also be referred to as CHECK ENGINE light.

ECM contains a self-diagnostic system which may store a Diagnostic Trouble Code (DTC) if an electronic control system failure exists. DTC may be retrieved from ECM for system diagnosis by using a scan tool. See SELF-DIAGNOSTIC SYSTEM. For ECM location (Scheme 15)- (Scheme 24).

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Scheme 24

INPUT DEVICES

Note. Components are grouped into 2 categories. First category covers INPUT DEVICES, which control or produce voltage signals monitored by the Engine Control Module (ECM). Second category covers OUTPUT SIGNALS, which are components controlled by the ECM.

Vehicles are equipped with different combinations of input devices. Not all devices are used on all models. Available input signals include the following

Accelerator Pedal Position Sensor (Land Cruiser)

Accelerator pedal position sensor is used with ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) for controlling of throttle operation. See ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) under AIR INDUCTION SYSTEM for additional information.

A/C Compressor Lock Sensor (Camry & Camry Solara)

A/C compressor lock sensor delivers one pulse input signal per engine revolution to Engine Control Module (ECM). If number ratio of A/C compressor speed divided by engine speed is smaller than a predetermined value, ECM will turn off A/C compressor. A/C lock sensor is located near front of A/C compressor.

A/C Switch (All Models)

When A/C is turned on, input signal is delivered to Engine Control Module (ECM). ECM uses input signal to control engine idle speed during A/C operation.

Air/Fuel (A/F) Sensor (Avalon Calif. Emission Vehicles, Camry 2.2L 4-Cyl. Calif. Emission Vehicles, Camry 3.0L V6 Calif. Emission Vehicles With A/T, Camry Solara 2.2L 4-Cyl. Calif. Emission Vehicles, Camry Solara 3.0L V6 Calif. Emission Vehicles With A/T, RAV4 Calif. Emission Vehicles, Sienna Calif. Emission Vehicles & 4Runner 3.4L V6 Calif. Emission Vehicles)

Air Fuel (A/F) sensor may also be referred to as A/F ratio sensor. Heated A/F sensor monitors exhaust gas oxygen content and delivers an input signal to Engine Control Module (ECM). ECM may use input signal to control fuel injection system. For A/F sensor location, see A/F SENSOR LOCATION table.

A/F SENSOR LOCATION

Airflow Meter (Avalon, Camry 3.0L V6, Camry Solara 3.0L V6, Land Cruiser, Sienna, Tacoma & 4Runner)

Note. Airflow meter may also be referred to as Mass Airflow (MAF) meter.

Airflow meter measures intake airflow volume. Input signal for airflow volume is sent from airflow meter to Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance), controlling fuel injection system and oxygen sensor heater. Airflow meter also contains an intake air temperature sensor which is used to measure intake air temperature. See INTAKE AIR TEMPERATURE SENSOR .

Battery Signal (Avalon, Camry, Camry Solara, Celica, RAV4, Sienna, Tacoma & 4Runner)

Battery voltage is always present at BATT terminal of Engine Control Module (ECM). When ignition is turned on, voltage for ECM operation is applied through EFI main relay to +B terminal on ECM. EFI main relay may also be referred to as EFI relay.

Battery Signal (Corolla)

Battery voltage is always present at BATT terminal of Engine Control Module (ECM). When ignition is turned on, voltage for ECM operation is applied through EFI main relay to +B terminal on ECM. EFI main relay may also be referred to as EFI relay or F-HTR relay.

Battery Signal (Land Cruiser)

Battery voltage is always present at BATT and +BM terminals of Engine Control Module (ECM). When ignition is turned on, voltage for ECM operation is applied through EFI main relay to +B and +B1 terminals on ECM. EFI main relay may also be referred to as EFI relay or ECD relay. Voltage is applied to IGSW terminal on ECM through IGN fuse.

Brakelight Signal (Avalon, Camry, Camry Solara, Corolla With 4-Speed A/T, Land Cruiser, Sienna & 4Runner 3.4L V6 With A/T)

Brakelight switch delivers an input signal to STP terminal of Engine Control Module (ECM) to indicate when brakes are applied. Input signal is mainly used for controlling fuel cut-off engine speed. Brakelight switch may also be referred to as stoplight switch.

Brakelight Signal (Celica With A/T, RAV4 With A/T, Tacoma & 4Runner 2.7L 4-Cyl.)

Brakelight switch delivers an input signal to BK terminal of Engine Control Module (ECM) to indicate when brakes are applied. Input signal is mainly used for controlling fuel cut-off engine speed. Brakelight switch may also be referred to as stoplight switch.

Camshaft & Crankshaft Position Sensors (Avalon, Camry 3.0L V6 & Camry Solara 3.0L V6)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located at flywheel end of front cylinder head, just below valve cover. Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system, engine idle speed control system, EGR system, heated oxygen sensor system and intake air control valve system.

Camshaft & Crankshaft Position Sensors (Camry 2.2L 4-Cyl. & Camry Solara 2.2L 4-Cyl.)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located at timing belt end of cylinder head, on firewall side of engine. Crankshaft position sensor is located behind lower timing belt cover, near crankshaft sprocket. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system and engine idle speed control system.

Camshaft & Crankshaft Position Sensors (Celica)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is a pick-up coil located in the distributor. Crankshaft position sensor is located behind lower timing belt cover, near crankshaft sprocket. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system, A/C-cut control system and EGR system.

Camshaft & Crankshaft Position Sensors (Corolla)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located just above intake manifold on cylinder head, at flywheel end of engine. Crankshaft position sensor is located on front of engine, near crankshaft pulley. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system and engine idle speed control system.

Camshaft & Crankshaft Position Sensors (Land Cruiser)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located behind driver's side upper timing belt cover, near camshaft sprocket. Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system.

Camshaft & Crankshaft Position Sensors (RAV4)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located at timing belt end of cylinder head, on firewall side of engine. Crankshaft position sensor is located behind lower timing belt cover, near crankshaft sprocket. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system and engine idle speed control system.

Camshaft & Crankshaft Position Sensors (Sienna)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located at flywheel end of front cylinder head, just below valve cover. Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system, engine idle speed control system, heated oxygen sensor system and intake air control valve system.

Camshaft & Crankshaft Position Sensors (Tacoma 2.4L 4-Cyl. & 2.7L 4-Cyl., & 4Runner 2.7L 4-Cyl.)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located at driver's side front corner of cylinder head, just in front of intake manifold. Crankshaft position sensor is located near crankshaft pulley, just above oil pan on driver's side of engine. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system and heated oxygen sensor system.

Camshaft & Crankshaft Position Sensors (Tacoma 3.4L V6 & 4Runner 3.4L V6)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor is located behind upper timing belt cover, near passenger's side camshaft sprocket. Crankshaft position sensor is located at front of engine, just above crankshaft pulley. ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system and heated oxygen sensor system.

EGR Gas Temperature Sensor (Avalon, Camry 3.0L V6, Camry Solara 3.0L V6, Tacoma 2.4L 4-Cyl. & 2.7L 4-Cyl., & 4Runner 2.7L 4-Cyl.)

EGR gas temperature sensor monitors EGR gas temperature and delivers an input signal to Engine Control Module (ECM). EGR gas temperature sensor is located near EGR valve.

EGR Position Sensor (Avalon, Camry 3.0L V6 & Camry Solara 3.0L V6)

EGR position sensor monitors movement of EGR valve and delivers an input signal to the Engine Control Module (ECM). ECM uses this input signal to obtain the correct amount of EGR valve opening in relation to the engine operation. EGR position sensor is mounted on EGR valve.

Electrical Load Signal (Avalon, Camry 3.0L V6, Camry Solara 3.0L V6 & Sienna)

An input signal is delivered to ELS and ELS2 terminals of Engine Control Module (ECM) to indicate when high electrical output is required. This signal is delivered when items such as headlights or rear window defroster are turned on. ECM uses input signal to maintain proper engine idle speed.

Electrical Load Signal (Camry 2.2L 4-Cyl., Camry Solara 2.2L 4-Cyl., Celica, Land Cruiser, RAV4, Tacoma 2.4L 4-Cyl 2RZ-FE & 4Runner 2.7L 4-Cyl. With A/T)

An input signal is delivered to ELS terminal of Engine Control Module (ECM) to indicate when high electrical output is required. This signal is delivered when items such as rear window defroster or headlights are turned on. ECM uses input signal to maintain proper engine idle speed.

Electrical Load Signal (Corolla)

An input signal is delivered to ELS1 and ELS2 terminals of Engine Control Module (ECM) to indicate when high electrical output is required. This signal is delivered when items such as rear window defroster or headlights are turned on. ECM uses input signal to maintain proper engine idle speed.

Engine Coolant Temperature (ECT) Sensor (All Models)

ECT contains a built-in thermistor in which resistance varies according to engine coolant temperature. ECT delivers an input signal to THW terminal of Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system, engine idle speed control system, heated oxygen sensor system (if equipped), EGR system (if equipped) and operation of electronically controlled transaxles/transmissions (if equipped). For ECT sensor location, see appropriate REMOVAL, OVERHAUL & INSTALLATION article.

Engine Cranking Signal (All Models)

While engine is cranking and voltage is applied to the starter, an input signal is also delivered to STA or NSW terminal of Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system.

Intake Air Temperature Sensor (Avalon, Camry 3.0L V6, Camry Solara 3.0L V6, Land Cruiser, Sienna, Tacoma & 4Runner)

Intake air temperature sensor is located in airflow meter. Intake air temperature sensor measures incoming intake air temperature and delivers an input signal to THA terminal of Engine Control Module (ECM). ECM may use input signal for controlling fuel injection system.

Intake Air Temperature Sensor (Camry 2.2L 4-Cyl., Camry Solara 2.2L 4-Cyl., Celica, Corolla & RAV4)

Intake air temperature sensor is mounted in air filter housing. Intake air temperature sensor measures incoming intake air temperature and delivers an input signal to THA terminal of Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system.

Knock Sensor (Avalon, Camry 3.0L V6, Camry Solara 3.0L V6, Land Cruiser & Sienna)

Knock sensors No. 1 and 2 monitor ignition knock conditions and deliver input signals to KNKR and KNKL terminals of Engine Control Module (ECM). ECM may use input signals for determining ignition timing (spark advance) and for controlling fuel injection system. For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

Knock Sensor (Camry 2.2L 4-Cyl., Camry Solara 2.2L 4-Cyl., Celica, Corolla, Tacoma 2.4L 4-Cyl. & 2.7L 4-Cyl., & 4Runner 2.7L 4-Cyl.)

Knock sensor monitors ignition knock conditions and delivers input signal to KNK terminal of Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system. For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

Knock Sensor (RAV4)

Knock sensor monitors ignition knock conditions and delivers input signal to KNK1 terminal of Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system. For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

Knock Sensor (Tacoma 3.4L V6 & 4Runner 3.4L V6)

Knock sensors No. 1 and 2 monitor ignition knock conditions and deliver input signals to KNK1 and KNK2 terminals of Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system. For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

Manifold Absolute Pressure (MAP) Sensor (Camry 2.2L 4-Cyl., Camry Solara 2.2L 4-Cyl., Celica, Corolla & RAV4)

MAP sensor monitors intake manifold intake air volume and delivers an input signal to Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system. For MAP sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

Oxygen Sensor (All Models)

Oxygen sensor monitors exhaust gas oxygen content and delivers an input signal to Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system. Some models may be equipped with more than one oxygen sensor. On some models, a heated oxygen sensor may be used. On heated oxygen sensors, a heater is used to warm oxygen sensor to improve oxygen sensor detection operation. Heater is controlled by ECM.

Park/Neutral Position Switch (A/T Models)

Park/Neutral Position (PNP) switch delivers an input signal to Engine Control Module (ECM) to indicate transaxle/transmission gear position. ECM may use input signal to control engine idle speed and fuel injection system. PNP switch is located on side of transaxle/transmission.

Power Steering Pressure Switch (Avalon, Camry, Camry Solara, Corolla, Sienna, Tacoma 3.4L V6 & 4Runner 3.4L V6)

Power steering pressure switch delivers an input signal to Engine Control Module (ECM) to indicate power steering pressure. ECM may use input signal to control engine idle speed. Power steering pressure switch may also be referred to as power steering oil pressure switch. Power steering pressure switch is located on power steering pump, near pressure hose.

Throttle Position (TP) Sensor (Avalon, Camry, Camry Solara, Celica, Corolla, RAV4, Sienna, Tacoma & 4Runner)

TP sensor is located on throttle body. TP sensor delivers an input signal indicating throttle position to Engine Control Module (ECM). ECM may use input signal for determining ignition timing (spark advance) and for controlling fuel injection system, idle speed control system and various other systems.

Throttle Position (TP) Sensor (Land Cruiser)

TP sensor is used with Electronic Throttle Control System (ETCS) for controlling of the throttle operation. See ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) under AIR INDUCTION SYSTEM for additional information.

Vapor Pressure Sensor (All Models)

Note. Vapor pressure sensor may also referred to as EVAP vapor pressure sensor. Vapor pressure sensor VSV may also be referred to as EVAP Vapor Pressure Sensor Vacuum Switching Valve (EVAP-VPSVSV).

Engine Control Module (ECM) monitors fuel tank pressure to determine if a leak or an abnormality exists in the EVAP system. A vapor pressure sensor Vacuum Switching Valve (VSV) is located in the vapor line to charcoal canister. ECM will operate vapor pressure sensor VSV, allowing vapor pressure sensor to monitor fuel tank pressure and EVAP system. Vapor pressure sensor delivers an input signal to ECM to indicate fuel tank pressure.

Vehicle Speed Sensor (Avalon, Camry, Camry Solara, Celica, Corolla, Land Cruiser, RAV4, Tacoma & 4Runner 2.7L 4-Cyl.)

Vehicle speed sensor is mounted near rear of transaxle/transmission. Vehicle speed sensor outputs a 4-pulse input signal for every revolution of the drive gear in transaxle/transmission to the instrument cluster where input signal is converted to a rectangular waveform and then sent to Engine Control Module (ECM). ECM determines vehicle speed by using input signal and may use input signal for controlling fuel injection system and electronically controlled automatic transaxle/transmission (if equipped).

Vehicle Speed Sensor (Sienna & 4Runner 3.4L V6)

Wheel speed sensors on each wheel deliver an input signal to Anti-Lock Brake System (ABS) Electronic Control Unit (ECU). ABS ECU converts input signals from wheel speed sensors to a 4-pulse input signal to the instrument cluster. Instrument cluster then converts 4-pulse input signal to a rectangular waveform and then sends input signal to Engine Control Module (ECM). ECM determines vehicle speed by using input signal. ECM uses input signal for controlling fuel injection system and electronic control of automatic transmission/transaxle.

4WD Switch (Tacoma & 4Runner)

On 4WD models, 4WD switch on transfer case delivers an input signal to 4WD terminal of Engine Control Module (ECM) to indicate 4WD operation.

OUTPUT SIGNALS

Note. Vehicles are equipped with different combinations of computer-controlled components. Not all components listed below are used on every vehicle. For theory and operation on each output component, refer to system indicated after component.

Engine Control Module (ECM) receives input from data sensors and switches, depending on model application, to control following components and sub-systems

Accelerator Pedal Position Sensor

See ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) under AIR INDUCTION SYSTEM.

A/C-Cut Control System

See IDLE SPEED under FUEL SYSTEM.

A/F Heater Relay

See FUEL DELIVERY under FUEL SYSTEM.

Circuit Opening Relay

See FUEL DELIVERY under FUEL SYSTEM.

EGR Vacuum Switching Valve (VSV)

See EXHAUST GAS RECIRCULATION (EGR) SYSTEM under EMISSION SYSTEMS.

Electronically Controlled Transmission/Transaxle

See TRANSMISSION/TRANSAXLE CONTROLS under MISCELLANEOUS CONTROLS.

Electronic Spark Advance System

See DISTRIBUTORLESS IGNITION SYSTEM and DISTRIBUTOR TYPE IGNITION SYSTEM under IGNITION SYSTEM.

EVAP Vacuum Switching Valve (VSV)

See EVAPORATIVE EMISSION (EVAP) SYSTEM under EMISSION SYSTEMS.

Fuel Pump

See FUEL DELIVERY under FUEL SYSTEM.

Fuel Pump Relay

See FUEL DELIVERY under FUEL SYSTEM.

Idle Speed Control System

See IDLE SPEED under FUEL SYSTEM.

See INTAKE AIR CONTROL VALVE SYSTEM under AIR INDUCTION SYSTEM.

Self-Diagnostic System

See SELF-DIAGNOSTIC SYSTEM .

Throttle Control Motor

See ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) under AIR INDUCTION SYSTEM.

Vapor Pressure Sensor Vacuum Switching Valve (EVAP-VPSVSV)

See EVAPORATIVE EMISSION (EVAP) SYSTEM under EMISSION SYSTEMS.

FUEL DELIVERY

Vehicles are equipped with different combinations of fuel system electrical components. For complete wiring circuit of electrical components on a specific model, see appropriate wiring diagram in WIRING DIAGRAMS article.

Scheme 25

1. A/F Heater Relay (Avalon Calif. Emission Vehicles, Camry 3.0L V6 Calif. Emission Vehicles With A/T, Camry Solara 3.0L V6 Calif. Emission Vehicles With A/T & Sienna Calif. Emission Vehicles) A/F heater relay may also be referred to as A/F HTR relay. Constant battery voltage is supplied from battery, through A/F heater fuse to one side of A/F heater relay. When A/F heater relay is energized by MREL terminal of Engine Control Module (ECM), A/F heater relay provides battery voltage to +B terminal at A/F sensor. For A/F heater relay location, see «A/F HEATER RELAY LOCATION»(ref-91198-S26114076532001030500000) table. A/F HEATER RELAY LOCATION Application Location Avalon, Camry & Camry Solara In Small Fuse Relay Box At Driver's Side Front Corner Of Engine Comparment, In Front Of Battery Sienna (1) (1) Located near ECM behind passenger's side of instrument panel and contains a 4-pin connector. (Scheme 25)

1. Circuit Opening Relay (Avalon, Camry & Camry Solara) Circuit opening relay controls fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to one side of circuit opening relay. When ignition is turned on, voltage is supplied through IGN fuse to other side of circuit opening relay. When proper input signals are delivered to Engine Control Module (ECM), circuit opening relay ground circuit is grounded at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. For circuit opening relay location, see «CIRCUIT OPENING RELAY LOCATION»(ref-91198-S19261621192001030500000) table.
2. Circuit Opening Relay (Celica) Circuit opening relay controls fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to one side of circuit opening relay. When engine is cranking, circuit opening relay receives a start signal which energizes circuit opening relay. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. When start signal is released from circuit opening relay, Engine Control Module (ECM) then controls ground circuit for circuit opening relay at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. For circuit opening relay location, see «CIRCUIT OPENING RELAY LOCATION»(ref-91198-S19261621192001030500000) table.
3. Circuit Opening Relay (Corolla) Circuit opening relay controls fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to both sides of circuit opening relay. EFI main relay may also be referred to as EFI relay or F-HTR relay. When proper input signals are delivered to Engine Control Module (ECM), circuit opening relay ground circuit is grounded at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. For circuit opening relay location, see «CIRCUIT OPENING RELAY LOCATION»(ref-91198-S19261621192001030500000) table.
4. Circuit Opening Relay (RAV4) Circuit opening relay controls fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to one side of circuit opening relay. When ignition is turned on, voltage is supplied to other side of circuit opening relay. When proper input signals are delivered to Engine Control Module (ECM), circuit opening relay ground circuit is grounded at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. For circuit opening relay location, see «CIRCUIT OPENING RELAY LOCATION»(ref-91198-S19261621192001030500000) table.
5. Circuit Opening Relay (Sienna) Circuit opening relay controls fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to one side of circuit opening relay. When ignition is turned on, voltage is supplied through IGN fuse to other side of circuit opening relay. When proper input signals are delivered to Engine Control Module (ECM), circuit opening relay ground circuit is grounded at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. For circuit opening relay location, see «CIRCUIT OPENING RELAY LOCATION»(ref-91198-S19261621192001030500000) table.
6. Circuit Opening Relay (Tacoma) Circuit opening relay controls fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to one side of circuit opening relay. When engine is cranking, circuit opening relay receives a start signal which energizes circuit opening relay. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. When start signal is released from circuit opening relay, Engine Control Module (ECM) then controls the ground circuit for circuit opening relay at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. For circuit opening relay location, see «CIRCUIT OPENING RELAY LOCATION»(ref-91198-S19261621192001030500000) table.
7. Circuit Opening Relay (4Runner) Circuit opening relay controls fuel pump circuit. When EFI main relay is energized, EFI main relay provides battery voltage to both sides of circuit opening relay. When proper input signals are delivered to Engine Control Module (ECM), circuit opening relay ground circuit is grounded at ECM terminal FC. Circuit opening relay then provides voltage to fuel pump for fuel pump operation. For circuit opening relay location, see «CIRCUIT OPENING RELAY LOCATION»(ref-91198-S19261621192001030500000) table.

CIRCUIT OPENING RELAY LOCATION (1)

1. EFI Main Relay (Avalon, Camry 3.0L V6 & Camry Solara 3.0L V6) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. EFI main relay is energized by MREL terminal of Engine Control Module (ECM). When EFI main relay is energized, EFI main relay provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of ECM. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
2. EFI Main Relay (Camry 2.2L 4-Cyl. & Camry Solara 2.2L 4-Cyl.) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. EFI main relay is energized when ignition is turned on by voltage supplied through IGN fuse to EFI main relay on vehicles not equipped with engine immobilizer system, or by MREL terminal of Engine Control Module (ECM) on vehicles equipped with engine immobilizer system. When EFI main relay is energized, EFI main relay provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of ECM. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
3. EFI Main Relay (Celica) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. When ignition is turned on, voltage is supplied through IGN fuse to other side of EFI main relay. EFI main relay is then energized and provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of Engine Control Module (ECM) when ignition is turned on. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
4. EFI Main Relay (Corolla) EFI main relay may also be referred to as EFI relay or F-HTR relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. EFI fuse may also be referred to as F-HTR fuse. When ignition is turned on, voltage is supplied through IGN fuse to other side of EFI main relay. EFI main relay is then energized and provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of Engine Control Module (ECM) when ignition is turned on. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
5. EFI Main Relay (Land Cruiser) EFI main relay may also be referred to as EFI relay or ECD relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. EFI fuse may also be referred to as ECD fuse. When EFI main relay is energized by MREL terminal of Engine Control Module (ECM), EFI main relay provides battery voltage to +B terminal of fuel pump Electronic Control Unit (ECU) and various other electrical components. EFI main relay also provides battery voltage to +B and +B1 terminals of ECM. For operation of fuel pump ECU and fuel pump switch, see «FUEL PUMP ELECTRONIC CONTROL UNIT (ECU) & FUEL PUMP SWITCH»(ref-91198-S04560479342001030500000) . For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
6. EFI Main Relay (RAV4) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. When ignition is turned on, voltage is supplied to other side of EFI main relay from the ignition switch. EFI main relay is then energized and provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of Engine Control Module (ECM) when ignition is turned on. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
7. EFI Main Relay (Sienna) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. EFI main relay is energized by MREL terminal of Engine Control Module (ECM). When EFI main relay is energized, EFI main relay provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of ECM. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
8. EFI Main Relay (Tacoma) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. When ignition is turned on, voltage is supplied through IGN fuse to other side of EFI main relay. EFI main relay is then energized and provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of Engine Control Module (ECM) when ignition is turned on. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
9. EFI Main Relay (4Runner 2.7L 4-Cyl.) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. When ignition is turned on, voltage is supplied through IGN fuse to other side of EFI main relay. EFI main relay is then energized and provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of ECM. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.
10. EFI Main Relay (4Runner 3.4L V6) EFI main relay may also be referred to as EFI relay. EFI fuse supplies constant battery voltage to one side of EFI main relay. EFI main relay is energized by MREL terminal of Engine Control Module (ECM). When EFI main relay is energized, EFI main relay provides battery voltage to circuit opening relay, data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B terminal of ECM. For EFI main relay location, see «EFI MAIN RELAY LOCATION»(ref-91198-S35692291402001030500000) table.

EFI MAIN RELAY LOCATION

Fuel Pump (Avalon, Camry, Camry Solara, Celica, Corolla, RAV4, Sienna, Tacoma & 4Runner)

Electric fuel pump is mounted in fuel tank. Fuel pump operates at one specified speed.

Fuel Pump (Land Cruiser)

Electric fuel pump is mounted in fuel tank. Fuel pump operating speed is varied by use of fuel pump Electronic Control Unit (ECU). For additional information, see FUEL PUMP ELECTRONIC CONTROL UNIT (ECU) & FUEL PUMP SWITCH .

Fuel Pump Electronic Control Unit (ECU) & Fuel Pump Switch (Land Cruiser)

Fuel pump operating speed is controlled by operating condition of the engine such as: starting, idling, light load or heavy load. Engine Control Module (ECM) delivers an input signal from FPC terminal on ECM to FPC terminal on fuel pump ECU in accordance with engine operating condition. Fuel pump ECU uses this input signal to determine how much voltage should be delivered to fuel pump for varying fuel pump operating speed. If a problem exists in fuel pump ECU or control circuit, Diagnostic Trouble Code (DTC) P1200 may be stored in ECM. See SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs. Fuel pump ECU is located behind inner panel, just behind driver's rear wheelwell. (Scheme 26)

Scheme 26

Fuel pump switch is in the circuit between FPC terminal on ECM and FPC terminal on fuel pump ECU. Fuel pump switch may also be referred to as fuel pump inertia switch or fuel pump control switch. If vehicle is involved in a collision, fuel pump switch will shut off fuel pump by opening this circuit, and not allowing any input signal to be delivered from ECM to fuel pump ECU. Fuel pump switch is located on driver's side of instrument panel. (Scheme 27) Fuel pump switch contains a reset switch which has an OFF and ON position. (Scheme 27) Continuity will exist between electrical terminals on fuel pump switch with reset switch in ON position, and no continuity in OFF position. Reset switch must be in ON position for fuel pump operation.

Scheme 27

Fuel Pressure Regulator (Avalon, Camry, Camry Solara, Corolla, RAV4 & Sienna)

Fuel system is a returnless type system with fuel pressure regulator mounted on the fuel pump in the fuel tank. Fuel pressure regulator maintains constant fuel pressure to the fuel injectors.

Fuel Pressure Regulator (Celica, Land Cruiser, Tacoma & 4Runner)

Mounted on fuel rail, vacuum-operated fuel pressure regulator maintains constant fuel pressure to fuel injectors. As throttle is depressed and manifold vacuum decreases, fuel pressure regulator increases fuel pressure to maintain a constant fuel flow to fuel injectors.

Fuel-Cut System (All Models)

Controlled through input signals, Engine Control Module (ECM) will shut off fuel delivery momentarily during closed throttle deceleration.

Fuel Injectors (All Models)

Fuel injectors are electrically operated solenoids which deliver fuel to individual cylinders. Engine Control Module (ECM) controls fuel injector duration based on various input signals to determine air/fuel mixture.

A/C-Cut Control System (Camry 2.2L 4-Cyl., Camry Solara 2.2L 4-Cyl., Celica, Corolla & RAV4)

Engine Control Module (ECM) uses various input signals for controlling A/C-cut control system. A/C-cut control system interrupts A/C compressor operation for a fixed period of time when vehicle accelerates from low engine speed.

Dashpot (Tacoma 3.4L V6 With M/T & 4Runner 3.4L V6 With M/T)

Dashpot is mounted on throttle body and is used to allow engine to slowly return to specified RPM after throttle is released.

Idle Speed Control System (Avalon, Camry, Camry Solara, Celica, Corolla, RAV4, Sienna, Tacoma & 4Runner)

Idle speed control system may also be referred to as idle air control system. Engine Control Module (ECM) is programmed with engine idle speed values. Idle speed control system provides a stable idle speed when engine is cold or idle speed decreases due to electrical load etc. ECM uses various input signals to maintain proper idle speed by controlling Idle Air Control (IAC) valve.

Throttle Control Motor (Land Cruiser)

Throttle control motor is used with ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) for controlling of the throttle operation and idle speed. See ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) under AIR INDUCTION SYSTEM for additional information.

Throttle Opener (Avalon, Camry, Camry Solara, Celica, RAV4, Sienna, Tacoma & 4Runner)

Throttle opener, mounted on throttle body, is vacuum controlled and allows engine to return to specified RPM after throttle is released.

DISTRIBUTORLESS IGNITION SYSTEM

Note. Distributorless ignition system may be referred to as Electronic Spark Advance (ESA) system.

Distributorless Ignition System (DIS) uses Engine Control Module (ECM) for determining ignition timing (spark advance). ECM may determine ignition timing (spark advance) based on various input signals, engine RPM and knock sensor input signals.

Conventional distributor and pick-up coil have been replaced by a camshaft position sensor and crankshaft position sensor. Camshaft position sensor may also be referred to as cam position sensor. Camshaft position sensor and crankshaft position sensor deliver input signals to ECM. ECM detects standard crankshaft position based on camshaft position sensor input signals and actual crankshaft position, and engine speed by crankshaft position sensor input signals. Camshaft position sensor is located at flywheel end of front cylinder head, just below valve cover. (Scheme 3), (Scheme 5) and (Scheme 10). Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. (Scheme 3), (Scheme 5) and (Scheme 10). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

ECM uses 3 ignition primary control signals to ignitor for ignition coils. DIS uses 3 ignition coils which fire 2 cylinders simultaneously using same ignition coil. (Scheme 28) Cylinder No. 1 is front cylinder on right side of engine when viewed from flywheel end of engine. Cylinder No. 2 is front cylinder on left side of engine when viewed from flywheel end of engine. Cylinders No. 1, 3 and 5 are on right side of engine. Cylinders No. 2, 4 and 6 are on left side of engine.

One ignition coil is mounted on top of spark plug on cylinders No. 2, 4 and 6. Spark plug wires are routed from ignition coils on top of spark plugs to spark plugs on remaining cylinders. ECM monitors IGF circuit at ignitor to ensure ignition coils have fired.

Scheme 28

Camry 2.2L 4-Cyl., Camry Solara 2.2L 4-Cyl., Corolla & RAV4

Distributorless Ignition System (DIS) uses Engine Control Module (ECM) for determining ignition timing (spark advance). ECM may determine ignition timing (spark advance) based on various input signals, engine RPM and knock sensor input signal.

Conventional distributor and pick-up coil have been replaced by a camshaft position sensor and crankshaft position sensor. Camshaft position sensor may also be referred to as cam position sensor. Camshaft position sensor and crankshaft position sensor deliver input signals to ECM. ECM detects standard crankshaft position based on camshaft position sensor input signals and actual crankshaft position, and engine speed by crankshaft position sensor input signals.

On Camry 2.4L 4-cylinder, Camry Solara 2.2L 4-cylinder and RAV4, camshaft position sensor is located at timing belt end of cylinder head, on firewall side of engine. (Scheme 4)and (Scheme 9). Crankshaft position sensor is located behind lower timing belt cover, near crankshaft sprocket. (Scheme 4)and (Scheme 9). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

On Corolla, camshaft position sensor is located just above intake manifold on cylinder head, at flywheel end of engine. (Scheme 7) Crankshaft position sensor is located on front of engine, near crankshaft pulley. (Scheme 7) For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

On all models, ECM uses 2 ignition primary control signals to ignitor on for ignition coils. DIS uses 2 ignition coils with internal ignitors to fire 2 cylinders simultaneously using same ignition coil. (Scheme 29) Cylinders No. 1 and 4 fire together and cylinders No. 2 and 3 fire together. Cylinder No. 1 is front cylinder at timing belt or timing chain end of engine and cylinder No. 4 is rear cylinder at flywheel end of engine. Ignition coils are mounted on end of cylinder head, just below valve cover. ECM monitors IGF circuit at ignitor to ensure ignition coils have fired. ECM stops fuel injection as a fail-safe function if IGF signal if ECM does not receive IGF signal.

Scheme 29

Distributorless Ignition System (DIS) uses Engine Control Module (ECM) for determining ignition timing (spark advance). ECM may determine ignition timing (spark advance) based on various input signals, engine RPM and knock sensor input signals.

Conventional distributor and pick-up coil have been replaced by a camshaft position sensor and crankshaft position sensor. Camshaft position sensor may also be referred to as cam position sensor. Camshaft position sensor and crankshaft position sensor deliver input signals to ECM. ECM detects standard crankshaft position based on camshaft position sensor input signals and actual crankshaft position, and engine speed by crankshaft position sensor input signals. Camshaft position sensor is located behind driver's side upper timing belt cover, near camshaft sprocket. (Scheme 8) Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. (Scheme 8) For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

The ECM uses 8 ignition primary control signals to ignitors for ignition coils. DIS uses 8 ignition coils with internal ignitors, one ignition coil for each cylinder. (Scheme 30) Cylinder No. 1 is front cylinder on left side of engine when viewed from flywheel end of engine. Cylinder No. 2 is front cylinder on right side of engine when viewed from flywheel end of engine. Cylinders No. 1, 3, 5 and 7 are on left side of engine. Cylinders No. 2, 4, 6 and 8 are on right side of engine. The ECM monitors IGF circuit at ignitor to ensure ignition coils have fired.

Scheme 30

Tacoma 2.4L 4-Cyl. & 2.7L 4-Cyl., & 4Runner 2.7L 4-Cyl.

Distributorless Ignition System (DIS) uses Engine Control Module (ECM) for determining ignition timing (spark advance). ECM may determine ignition timing (spark advance) based on various input signals, engine RPM and knock sensor input signal.

Conventional distributor and pick-up coil have been replaced by a camshaft position sensor and crankshaft position sensor. Camshaft position sensor may also be referred to as cam position sensor. Camshaft position sensor and crankshaft position sensor deliver input signals to ECM. ECM detects standard crankshaft position based on camshaft position sensor input signals and actual crankshaft position, and engine speed by crankshaft position sensor input signals. Camshaft position sensor is located at driver's side front corner of cylinder head, just in front of intake manifold. (Scheme 11)and (Scheme 13). Crankshaft position sensor is located near crankshaft pulley, just above oil pan on driver's side of engine. (Scheme 11)and (Scheme 13). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

ECM uses 2 ignition primary control signals to ignitor for the ignition coils. DIS uses 2 ignition coils with internal ignitors to fire 2 cylinders simultaneously using same ignition coil. (Scheme 29) Cylinders No. 1 and 4 fire together and cylinders No. 2 and 3 fire together. Cylinder No. 1 is front cylinder at timing chain end of engine and cylinder No. 4 is the rear cylinder at flywheel end of engine. Ignition coils are mounted near front of cylinder head. ECM monitors IGF circuit at the ignitor to ensure ignition coils have fired.

Tacoma 3.4L V6 & 4Runner 3.4L V6

Distributorless Ignition System (DIS) uses Engine Control Module (ECM) for determining ignition timing (spark advance). ECM may determine ignition timing (spark advance) based on various input signals, engine RPM and knock sensor input signals.

Conventional distributor and pick-up coil have been replaced by a camshaft and crankshaft position sensor. Camshaft position sensor may also be referred to as cam position sensor. Camshaft position sensor and crankshaft position sensor deliver input signals to ECM. ECM detects standard crankshaft position based on camshaft position sensor input signals and actual crankshaft position, and engine speed by crankshaft position sensor input signals. Camshaft position sensor is located behind upper timing belt cover, near passenger's side camshaft sprocket. (Scheme 12)and (Scheme 14). Crankshaft position sensor is located at front of engine, just above crankshaft pulley. (Scheme 12)and (Scheme 14). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

ECM uses 3 ignition primary control signals to ignitor for ignition coils. (Scheme 31) DIS uses 3 ignition coils which fire 2 cylinders simultaneously using same ignition coil. Cylinders No. 1 and 4 fire together, 2 and 5 fire together, and 3 and 6 fire together. Cylinder No. 1 is front cylinder on right side of engine when viewed from flywheel end of engine. Cylinder No. 2 is front cylinder on left side of engine when viewed from flywheel end of engine. Cylinders No. 1, 3 and 5 are on right side of engine. Cylinders No. 2, 4 and 6 are on left side of engine.

One ignition coil is mounted on top of spark plug on cylinder No. 1 with spark plug wire going to cylinder No. 4 spark plug. One ignition coil is mounted on top of spark plug on cylinder No. 3 with spark plug wire going to cylinder No. 6 spark plug. One ignition coil is mounted on top of spark plug on cylinder No. 5 with spark plug wire going to cylinder No. 2 spark plug. ECM monitors IGF circuit at ignitor to ensure ignition coils have fired.

Scheme 31

DISTRIBUTOR TYPE IGNITION SYSTEM

Note. Distributor type ignition system may be referred to as Electronic Spark Advance (ESA) system.

Celica

Ignition system uses Engine Control Module (ECM) for determining ignition timing (spark advance). ECM may determine ignition timing (spark advance) based on various input signals, engine RPM and knock sensor input signal. Ignition coil is a mounted in the engine compartment.

Camshaft position sensor (pick-up coil) and crankshaft position sensor deliver input signals to ECM. Camshaft position sensor in the distributor may be referred to as pick-up coil in distributor. ECM detects standard crankshaft position based on camshaft position sensor input signal and actual crankshaft position, and engine speed by crankshaft position sensor input signals. Crankshaft position sensor is located behind lower timing belt cover, near crankshaft sprocket. (Scheme 6)

ECM determines ignition timing and delivers an output ignition signal to ignitor on IGT wire. Since width of IGT signal is constant, dwell angle control circuit in the ignitor determines the time the control circuit starts primary current flow to ignition coil based on engine RPM and ignition timing one revolution ago.

When ignition timing in obtained, primary circuit is turned off when ECM delivers a signal to ignitor on IGT wire, causing ignition coil to fire the spark plug. After delivering a command to turn off primary circuit on IGT wire, ECM monitors IGF circuit to ignitor to ensure primary switching occurred. ECM stops fuel injection as a fail-safe function when IGF reference signal has not been received.

Avalon, Camry 3.0L V6 & Camry Solara 3.0L V6

EGR system reduces oxides of nitrogen (NOx) emissions by lowering combustion temperatures. Combustion temperatures are lowered by recycling metered amount of exhaust gases back into intake system.

EGR system contains a vacuum-operated EGR valve, EGR Vacuum Control Valve (VCV), EGR position sensor and a vacuum tank. (Scheme 32) An EGR gas temperature sensor is screwed into lower side of EGR valve.

EGR VCV regulates intake manifold vacuum applied to EGR Vacuum Switching Valve (VSV). EGR operation is controlled by EGR VSV which is operated by Engine Control Module (ECM). EGR position sensor monitors movement of EGR valve and delivers an input signal to the ECM. The ECM uses this input signal to obtain the correct amount of EGR valve opening in relation to engine operation. ECM uses various input signals for controlling EGR VSV. For EGR system and component testing, see SYSTEM & COMPONENT TESTING - V6 & V8 article.

Scheme 32

Camry 2.2L 4-Cyl., Camry Solara 2.2L 4-Cyl., Celica, RAV4, Tacoma 2.4L 4-Cyl. & 2.7L 4-Cyl., & 4Runner 2.7L 4-Cyl.

EGR system reduces oxides of nitrogen (NOx) emissions by lowering combustion temperatures. Combustion temperatures are lowered by recycling metered amount of exhaust gases back into intake system. EGR system contains a vacuum-operated EGR valve, EGR vacuum modulator and EGR Vacuum Switching Valve (VSV). (Scheme 33) EGR vacuum modulator regulates exhaust backpressure and balances atmospheric pressure and vacuum to allow EGR operation at heavy throttle. EGR valve operation is controlled by EGR VSV which is controlled by Engine Control Module (ECM).

The ECM uses various input signals for controlling EGR system operation. For EGR system and component testing, see SYSTEM & COMPONENT TESTING - 4-CYLINDER article.

Scheme 33

EVAPORATIVE EMISSION (EVAP) SYSTEM

Note. EVAP may also be referred to as fuel evaporation.

EVAP system prevents fuel tank gasoline vapors from escaping into the atmosphere. Fuel tank gasoline vapors are routed through EVAP canister into air cleaner and intake manifold for combustion in the cylinders. (Scheme 34)

Engine Control Module (ECM) monitors fuel tank pressure to determine if a leak or an abnormality exists in the EVAP system. A vapor pressure sensor Vacuum Switching Valve (VSV) is located in vapor line to EVAP canister. Vapor pressure sensor VSV may also be referred to as EVAP Vapor Pressure Sensor Vacuum Switching Valve (EVAP-VPSVSV).

ECM will operate vapor pressure VSV, allowing vapor pressure sensor to monitor fuel tank pressure and EVAP system. Vapor pressure sensor delivers an input signal to ECM to indicate fuel tank pressure. If a leak or an abnormality exists in the EVAP system, a Diagnostic Trouble Code (DTC) will be stored in ECM. Vapor pressure sensor may be referred to as EVAP vapor pressure sensor.

An EVAP Vacuum Switching Valve (VSV) is used to control EVAP system. ECM operates EVAP VSV which controls vacuum flow for EVAP operation. For EVAP system and component testing, see appropriate SYSTEM & COMPONENT TESTING article.

Scheme 34

Avalon, Camry, Camry Solara, Celica & Corolla

ORVR system is used to recover fuel vapors into EVAP canister that are generated during refueling. ORVR system consists of fuel inlet pipe, overfill check valve and EVAP canister. (Scheme 35)

When fuel tank cap is removed, atmospheric pressure is applied to port "A" on overfill check valve. (Scheme 36) Overfill check valve may also be referred to as ORVR-OCKV or fill check valve. When fuel flows into fuel inlet pipe and fuel tank, the pressure in fuel tank increases. Increased pressure in fuel tank causes valve "B" on overfill valve to open, allowing fuel vapors to flow into EVAP canister. When fuel tank is full, valve "C" closes, shutting off vapor flow to EVAP canister.

Scheme 35

Scheme 36

POSITIVE CRANKCASE VENTILATION

Positive Crankcase Ventilation (PCV) system prevents crankcase vapors from escaping into the atmosphere. Crankcase vapors are routed from crankcase through a vacuum-controlled PCV valve and then delivered back into the cylinders. PCV system provides primary control of crankcase blow-by vapors, according to manifold vacuum. When manifold vacuum is high (at idle), PCV restricts vapor flow to maintain a smooth idle condition.

MISCELLANEOUS CONTROLS

Note. Although not considered true engine performance-related systems, some controlled devices may affect driveability if the malfunction.

TRANSMISSION/TRANSAXLE CONTROLS

Note. Only electronically controlled transmissions/transaxles are covered. Some models have transmissions and transaxles that are not electronically controlled.

Electronically Controlled Transmission/Transaxle (ECT)

Engine Control Module (ECM) uses input signals for controlling transmission/transaxle operation.