Engine Controls - Theory & Operation Toyota Camry Solara I

INTRODUCTION

Note. References to California models apply to California emission vehicles, which may be verified by underhood Emission Control label. California emissions may be available in other states.

This article covers basic description and operation of engine performance-related systems and components. Read this article before diagnosing vehicles or systems with which you are not completely familiar.

ACOUSTIC CONTROL INDUCTION SYSTEM (ACIS)

Note. ACIS may also be referred to as intake air control valve system.

Avalon

ACIS is a variable induction system that improves engine performance by increasing the length of intake runners in the air intake chamber. In accordance with engine speed and throttle opening angle, ACIS controls the length of intake runners in air intake chamber in 3 stages by opening and closing the 2 intake air control valves located on end of air intake chamber and downstream of the throttle valves. (Scheme 1)

When engine is under a heavy load and vehicle speed is low, Engine Control Module (ECM) turns on both ACIS Vacuum Switching Valves (VSVs) resulting in vacuum being supplied from vacuum tank to both actuators for the intake air control valves. This results in both intake air control valves closing, enabling the air intake chamber, throttle bodies and air cleaner hose to function as an intake manifold. When engine is under a medium load and vehicle speed in the mid-range, ECM turns on ACIS VSV at the air intake chamber side and turns off ACIS VSV downstream of the throttle valves. As a result, the intake air control valve in the air intake chamber closes and intake air control valve downstream of the throttle valves opens, enabling air intake chamber to function as the intake manifold. When engine is idling, engine is under a light load or vehicle speed is high, ECM turns off both ACIS VSVs. This allows both intake air control valves to open, enabling air intake chamber to function as a normal air intake chamber. ECM uses an engine RPM input signal and throttle position sensor input signal for determining ACIS operation. Engine RPM input signal is provided by camshaft and crankshaft position sensors.

Scheme 1

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

ACIS is a variable induction system that improves engine performance by increasing the length of intake runners in the air intake chamber. In accordance with engine speed and throttle opening angle, ACIS controls the length of intake runners in air intake chamber in 2 stages by opening and closing the intake air control valve located on end of air intake chamber. (Scheme 2) ACIS is controlled by Engine Control Module (ECM). ECM controls ACIS Vacuum Switching Valve (VSV) which controls vacuum supply from vacuum tank to the actuator, which operates intake air control valve in air intake chamber. ECM uses engine RPM input signal and throttle position sensor input signal for determining ACIS operation. Engine RPM input signal is provided by camshaft and crankshaft position sensors.

Scheme 2

Celica

ACIS is a variable induction system that improves engine performance and reduces engine noise by dividing the air intake duct into 2 stages. When engine is operating in low-to-mid speed range, ACIS causes variable intake valve to close one side of the intake air duct. (Scheme 3) When engine is operating in the high-speed range, ACIS causes variable intake valve to open, allowing both sides of the intake air duct to supply intake air. Variable intake valve operation is controlled by a vacuum controlled actuator. (Scheme 3) Engine Control Module (ECM) controls the ACIS Vacuum Switching Valve (VSV) which controls vacuum supply from vacuum tank to the actuator. (Scheme 3) ECM uses engine RPM input signal and throttle position sensor input signal for determining ACIS operation. Engine RPM input signal is provided by camshaft and crankshaft position sensors.

Scheme 3

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 & Tundra 4.7L V8

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 4) 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. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs. 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 4)

Scheme 4

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 5)- (Scheme 20). 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 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Avalon, Camry Gasoline Models, 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 SYSTEMS. For ECM location (Scheme 21)- (Scheme 32).

Scheme 21

Scheme 22

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Scheme 32

VARIABLE VALVE LIFT (VVL) SYSTEM

Note. VVL system may also be referred to as Variable Valve Timing Lift Intelligent (VVTL-I or VVTL-i) system.

Celica (1.8L 2ZZ-GE)

The VVL system controls amount of intake and exhaust valve lift while engine is operating at high speeds to provide improved engine performance and fuel economy. VVL system consists of Oil Control Valve (OCV), camshaft changeover mechanism, camshaft position sensor, crankshaft position sensor, engine coolant temperature sensor, camshafts with low-and-medium-speed camshaft lobes and high-speed camshaft lobes, Engine Control Module (ECM) and associated wiring. (Scheme 33)

Note. OCV for VVL system may also be referred to as camshaft timing oil control valve (VVL) or Variable Valve Lift (VVL) oil control valve.

When engine is operating in low-to-medium-speed range, low-and-medium-speed camshaft lobes operate to move the valves by using needle roller and rocker arm on camshaft changeover mechanism. (Scheme 33) The high-speed camshaft lobes also push downward on the rocker arm pad, but because rocker arm pad moves freely, this movement of high-speed camshaft lobes does not cause the rocker arm to move the valves. When engine coolant temperature is greater than 140°F (60°C) with engine speed greater than 6000 RPM, the Engine Control Module (ECM) operates oil control valve for VVL system to allow oil pressure to be applied to the rocker arm pin. (Scheme 33) When oil pressure is applied to rocker arm pin, rocker arm pin is pushed to the locked position. This prevents rocker arm pad from moving freely and this changes operation from low-and-medium-speed camshaft lobes to the high-speed camshaft lobes to provide more valve lift for improved engine performance and fuel economy.

Oil control valve for VVT is an electrically controlled valve that receives oil pressure from the oil pump. (Scheme 34) When engine is operating in low-to-medium-speed range, ECM operates oil control valve to move spool valve to open position. This allows oil pressure to drain instead of being applied to rocker arm pin for use of high-speed camshaft lobes. When engine coolant temperature is greater than 140°F (60°C) with engine speed greater than 6000 RPM, ECM operates oil control valve to move spool valve to the closed position. This allows oil pressure to be applied to rocker arm pin for use of the high-speed camshaft lobes. The ECM uses input signals for engine speed, intake air volume, throttle position and engine coolant temperature to determine operation of oil control valve for VVT.

If a problem exists in the VVL system, Diagnostic Trouble Code (DTC) may be stored in ECM. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs.

Scheme 33

Scheme 34

VARIABLE VALVE TIMING (VVT) SYSTEM

Note. VVT system may also be referred to as Variable Valve Timing Intelligent (VVT-I or VVT-i) system.

The VVT system controls intake camshaft valve timing to provide improved engine performance and fuel economy, and reduce exhaust emissions. VVT system consists of 2 camshaft timing oil control valves, variable valve timing controller on each intake camshaft, crankshaft position sensor, engine coolant temperature sensor, Engine Control Module (ECM), variable valve timing sensors and associated wiring. (Scheme 35)

Note. Camshaft timing oil control valve may also be referred to as VVT camshaft timing oil control valve, camshaft timing oil control valve VVT, oil control valve for VVT or VVT Oil Control Valve (OCV). Variable valve timing controller may also be referred to as variable valve timing actuator or Variable Valve Timing (VVT) controller.

Exhaust camshaft is driven by the timing belt and intake camshaft is driven by gear on the end of exhaust camshaft. Intake camshaft drive gear is integrated with the variable valve timing controller to vary intake camshaft valve timing. Variable valve timing controller consists of a housing driven from the exhaust camshaft and a vane that is fixed on the intake camshaft. (Scheme 36) Oil pressure may be delivered from the advance or retard side of the intake camshaft to the variable valve timing controller. This oil pressure causes variable valve timing controller to rotate, causing intake camshaft to rotate and change the valve timing. When engine is stopped, to improve stability, intake camshaft will be placed in the most retarded state. At this time, a lock pin secures the housing and the vane inside the variable valve timing controller. After the engine starts, lock pin is released by oil pressure.

Camshaft timing oil control valve is an electrically controlled valve that receives oil pressure from the oil pump. (Scheme 37) The ECM uses input signals for engine speed, intake air volume, throttle position and engine coolant temperature to determine operation of camshaft timing oil control valve. The ECM also uses input signals from variable valve timing sensors and crankshaft position sensor for determining the actual intake camshaft valve timing. Variable valve timing sensors may also be referred to as camshaft position sensors. The ECM operates camshaft timing oil control valve by controlling position of spool valve to determine which side of variable valve timing controller the oil pressure will be applied on for advancing or retarding the valve timing by rotating the intake camshaft. (Scheme 37) When engine is stopped, camshaft timing oil control valve is in the retarded state.

When engine is idling, intake camshaft valve timing is set at the standard or hold position to stabilize the idle and obtain better fuel economy. During light engine load, intake camshaft valve timing is retarded to provide stable engine operation. During medium engine load, intake camshaft valve timing is advanced to provide increased fuel economy and improved emission control. During heavy engine load in low-to-medium-speed range, intake camshaft valve timing is advanced to provide increased torque. During heavy engine load in high-speed range, intake camshaft valve timing is retarded to provide improved high-speed range operation and better fuel economy. During cold temperatures, intake camshaft valve timing is set at the standard or hold position to stabilize fast idle speed and obtain better fuel economy. When engine is started or stopped, intake camshaft valve timing is set at the standard or hold position to improve engine starting.

If a problem exists in the VVT system, Diagnostic Trouble Code (DTC) may be stored in ECM. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs.

Scheme 35

Scheme 36

Scheme 37

Celica, Corolla & ECHO

The VVT system controls intake camshaft valve timing to provide improved engine performance and fuel economy, and reduce exhaust emissions. VVT system consists of camshaft timing oil control valve, variable valve timing controller on intake camshaft, crankshaft position sensor, Engine Control Module (ECM), camshaft position sensor and associated wiring. (Scheme 38)and (Scheme 39).

Note. Camshaft timing oil control valve may also be referred to as oil control valve for VVT, VVT Oil Control Valve (OCV) or camshaft timing oil control valve VVT. Variable valve timing controller may also be referred to as variable valve timing actuator or Variable Valve Timing (VVT) controller.

Intake and exhaust camshaft are driven by a timing chain and drive gear on each camshaft. Intake camshaft drive gear is integrated with the variable valve timing controller to vary intake camshaft valve timing. Variable valve timing controller consists of a housing which is driven from the timing chain and a vane that is fixed on the intake camshaft. (Scheme 40) Oil pressure may be delivered from advance or retard side of intake camshaft to the variable valve timing controller. This oil pressure causes variable valve timing controller to rotate, causing intake camshaft to rotate and change the valve timing. When engine is stopped, to improve stability, intake camshaft will be placed in the most retarded state. When no oil pressure is applied to variable valve timing controller immediately after engine is started, lock pin prevents movement of variable valve timing controller to prevent a knocking noise. Once engine is started and oil pressure exists at variable valve timing controller, the lock pin is released by the oil pressure.

Camshaft timing oil control valve is an electrically controlled valve that receives oil pressure from the oil pump. (Scheme 37) The ECM uses input signals for engine speed, intake air volume, throttle position and engine coolant temperature to determine operation of camshaft timing oil control valve. The ECM also uses input signals from camshaft position sensor and crankshaft position sensor for determining the actual intake camshaft valve timing. Camshaft position sensor may also be referred to as variable valve timing sensor. The ECM operates camshaft timing oil control valve by controlling position of spool valve to determine which side of variable valve timing controller the oil pressure will be applied on for advancing or retarding the valve timing by rotating the intake camshaft. (Scheme 37) When engine is stopped, camshaft timing oil control valve is in the retarded state.

When engine is idling, intake camshaft valve timing is set at the standard or hold position to stabilize the idle and obtain better fuel economy. During light engine load, intake camshaft valve timing is retarded to provide stable engine operation. During medium engine load, intake camshaft valve timing is advanced to provide increased fuel economy and improved emission control. During heavy engine load in low-to-medium-speed range, intake camshaft valve timing is advanced to provide increased torque. During heavy engine load in high-speed range, intake camshaft valve timing is retarded to provide improved high-speed range operation and better fuel economy. During cold temperatures, intake camshaft valve timing is set at the standard or hold position to stabilize fast idle speed and obtain better fuel economy. When engine is started or stopped, intake camshaft valve timing is set at the standard or hold position to improve engine starting.

If a problem exists in the VVT system, Diagnostic Trouble Code (DTC) may be stored in ECM. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs.

Scheme 38

Scheme 39

Scheme 40

INPUT DEVICES

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 & Tundra 4.7L V8)

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 2.2L 4-Cyl. CNG Models, Camry 2.2L 4-Cyl. Gasoline Models With Manual A/C & Camry Solara 2.2L 4-Cyl. Models With Manual A/C)

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 Evaporator Temperature Sensor (Camry 2.2L 4-Cyl. CNG Models, Camry 2.2L 4-Cyl. Gasoline Models With Manual A/C & Camry Solara 2.2L 4-Cyl. With Manual A/C)

A/C evaporator temperature sensor detects temperature inside A/C cooling unit and delivers input signal to Engine Control Module (ECM). A/C evaporator temperature sensor is located inside A/C cooling unit, near A/C evaporator core.

A/C Switch (All Models)

When A/C is turned on, input signal is delivered to Engine Control Module (ECM). ECM may use input signal to control engine idle speed during A/C operation. Input signal may be delivered from A/C switch, A/C amplifier, A/C control assembly or A/C clutch depending on model application.

Air/Fuel (A/F) Sensor (Avalon, Camry 2.2L 4-Cyl. CNG Models, Camry 2.2L 4-Cyl. Gasoline Models With Calif. Emissions, Camry 3.0L V6 Calif. Emission Vehicles, Camry Solara 2.2L 4-Cyl. Calif. Emission Vehicles, Camry Solara 3.0L V6 Calif. Emission Vehicles, RAV4 Calif. Emission Vehicles, Sienna Calif. Emission Vehicles, Tacoma 2.4L 4-Cyl. Calif. Emission Vehicles, Tacoma 2.7L 4-Cyl. Calif. Emission Vehicles, Tacoma 3.4L V6 Calif. Emission Vehicles, Tundra 3.4L V6 Calif. Emission Vehicles, 4Runner 2.7L 4-Cyl. 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, Celica, Corolla, ECHO, Land Cruiser, Sienna, Tacoma, Tundra & 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 signals for determining ignition timing (spark advance), for 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, ECHO, RAV4, Sienna, Tacoma, Tundra 3.4L V6 & 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 & Tundra 4.7L V8)

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, Celica, Corolla With A/T, ECHO, Land Cruiser, Sienna, Tacoma Calif. Emission Vehicles, Tundra & 4Runner)

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 (RAV4 With A/T & Tacoma Except Calif. Emission Vehicles)

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)

Camshaft position sensors and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensors may also be referred to Variable Valve Timing (VVT) sensors. Camshaft position sensors are located at flywheel end of each 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, Acoustic Control Induction System (ACIS) and VVT system.

Camshaft & Crankshaft Position Sensors (Camry 2.2L 4-Cyl. CNG & Gasoline Models, & 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 (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 Acoustic Control Induction System (ACIS).

Camshaft & Crankshaft Position Sensors (Celica, Corolla & ECHO)

Camshaft position sensor and crankshaft position sensor deliver input signals to Engine Control Module (ECM). Camshaft position sensor may also be referred to Variable Valve Timing (VVT) sensor. On Celica and Corolla, camshaft position sensor is located just above intake manifold on cylinder head, at flywheel end of engine. On ECHO, camshaft position sensor is located on end of cylinder head at flywheel end of engine. On all models, 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, engine idle speed control system and VVT 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 Acoustic Control Induction System (ACIS).

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, Tundra 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.

Camshaft & Crankshaft Position Sensors (Tundra 4.7L V8)

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.

Center Air Bag Sensor Assembly (Camry 2.2L CNG Models, Celica & Corolla)

Center air bag sensor assembly delivers an input signal to Engine Control Module (ECM) if an airbag is deployed. If ECM detects air bags are deployed, ECM will stop fuel pump operation by opening the circuit opening relay. This operation is referred to fuel cut control. If fuel cut control has been activated, turning ignition switch from OFF position to ON position cancels the fuel cut control operation and fuel pump will operate.

EGR Gas Temperature Sensor (Camry 3.0L V6, Camry Solara 3.0L V6, Tacoma 2.4L 4-Cyl. 2RZ-FE Except Calif. Emission Vehicles, Tacoma 2.7L 4-Cyl. 3RZ-FE & 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 (Camry 3.0L V6 & Camry Solara 3.0L V6)

EGR position sensor monitors movement of EGR valve and delivers an input signal to 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 may also be referred to as EGR valve position sensor. 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 may use input signal to maintain proper engine idle speed.

Electrical Load Signal (Camry 2.2L 4-Cyl. CNG & Gasoline Models, Camry Solara 2.2L 4-Cyl., Land Cruiser, RAV4, Tacoma 2.4L 4-Cyl. 2RZ-FE, Tundra 4.7L V8 & 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 may use input signal to maintain proper engine idle speed.

Electrical Load Signal (Corolla)

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 rear window defroster or headlights are turned on. ECM may use input signal to maintain proper engine idle speed.

Electrical Load Signal (ECHO)

On vehicles equipped for cold areas, an input signal is delivered to ELS terminal of Engine Control Module (ECM) to indicate when high electrical output is required when HTR SUB1 relay is energized to provide voltage to Positive Temperature Coefficient (PTC) heater. PTC heater is a small electrical heater located in the heater core. PTC heater will be turned on when engine coolant temperature is less than 176°F (80°C), engine speed is greater than 1050 RPM, generator power ratio is less than 95 percent and heater temperature control switch is positioned in maximum heat range. ECM may use 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.

Fuel Pipe Fuel Pressure Sensor (Camry 2.2L 4-Cyl. CNG Models)

Fuel pipe fuel pressure sensor delivers input signal to Engine Control Module (ECM). ECM may use input signal to determine fuel line pressure for fuel gauge operation. Fuel pipe fuel pressure sensor may also be referred to as fuel pressure sensor (fuel pipe). Fuel pipe fuel pressure sensor is located near fuel pressure regulator located in the fuel line between fuel tank and the fuel rail, just below the brake booster. (Scheme 41)

Scheme 41

Fuel Rail Fuel Pressure Sensor (Camry 2.2L 4-Cyl. CNG Models)

Fuel rail fuel pressure sensor delivers input signal to Engine Control Module (ECM). ECM may use input signal to help correct the fuel injection volume. Fuel rail fuel pressure sensor may also be referred to as delivery pipe fuel pressure sensor or fuel pressure sensor (delivery pipe). Fuel rail fuel pressure sensor is located on end of fuel rail, near discharge valve.

Fuel Rail Fuel Temperature Sensor (Camry 2.2L 4-Cyl. CNG Models)

Fuel rail fuel temperature sensor delivers input signal to Engine Control Module (ECM). ECM may use input signal to help correct the fuel injection volume. Fuel rail fuel temperature sensor may also be referred to as delivery pipe fuel temperature sensor or fuel temperature sensor (delivery pipe). Fuel rail fuel temperature sensor is located at center of the fuel rail.

Fuel Tank Fuel Temperature Sensor (Camry 2.2L 4-Cyl. CNG Models)

Fuel tank fuel temperature sensor delivers input signal to Engine Control Module (ECM). ECM may use input signal to determine fuel tank temperature for fuel gauge operation. Fuel tank fuel temperature sensor may also be referred to as fuel temperature sensor (fuel tank). Fuel tank fuel temperature sensor is located on end of fuel tank behind the rear seat, near fuel tank fuel shutoff valve. (Scheme 42)

Scheme 42

Heated Oxygen Sensor (All Models)

Heated 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 heated oxygen sensor. A heater is used to warm oxygen sensor to improve heated oxygen sensor detection operation. Heater is controlled by ECM.

Intake Air Temperature Sensor (Avalon, Camry 3.0L V6, Camry Solara 3.0L V6, Celica, Corolla, ECHO, Land Cruiser, Sienna, Tacoma, Tundra & 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 determining ignition timing (spark advance), and for controlling fuel injection system.

Intake Air Temperature Sensor (Camry 2.2L 4-Cyl. CNG & Gasoline Models, Camry Solara 2.2L 4-Cyl. & 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 & Tundra 4.7L V8)

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. Gasoline Models, Camry Solara 2.2L 4-Cyl., Celica, Corolla, ECHO, RAV4, 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 or 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, Tundra 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. CNG & Gasoline Models, Camry Solara 2.2L 4-Cyl. & 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.

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 Sensor (ECHO)

Power steering pressure sensor 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 sensor may also be referred to as power steering oil pressure sensor. Power steering pressure sensor is located on side of power steering pump.

Power Steering Pressure Switch (Avalon, Camry, Camry Solara, Celica, Corolla, Sienna, Tacoma 2.4L 2RZ-FE Calif. Emission Vehicles, Tacoma 2.7L 3RZ-FE Calif. Emission Vehicles, Tacoma 3.4L V6, Tundra 3.4L V6, 4Runner 2.7L 4-Cyl. Calif. Emission Vehicles & 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.

Temperature Control Switch (ECHO)

On vehicles equipped for cold areas, temperature control switch operates a maximum hot switch which provides an input signal to Engine Control Module (ECM) for controlling Positive Temperature Coefficient (PTC) heater. PTC heater is a small electrical heater located in the heater core. Maximum hot switch may also be referred to as MAX HOT switch. For additional information on PTC heater, see POSITIVE TEMPERATURE COEFFICIENT (PTC) HEATER under MISCELLANEOUS CONTROLS.

Throttle Position (TP) Sensor (Avalon, Camry, Camry Solara, Celica, Corolla, ECHO, RAV4, Sienna, Tacoma, Tundra 3.4L V6 & 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 & Tundra 4.7L V8)

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 (Avalon, Camry 2.2L 4-Cyl. Gasoline Models, Camry 3.0L V6, Camry Solara, Celica & Corolla)

Vapor pressure sensor, pressure switching valve Vacuum Switching Valve (VSV) and canister closed valve Vacuum Switching Valve (VSV) are used to determine if a leak or an abnormality exists in the EVAP system. (Scheme 43) Engine Control Module (ECM) determines if a leak or an abnormality exists in EVAP system by using input signal from vapor pressure sensor. Vapor pressure sensor may also referred to as EVAP vapor pressure sensor. Canister closed valve Vacuum Switching Valve (VSV) may also be referred to as EVAP Canister Closed Valve Vacuum Switching Valve (EVAP-CCVVSV). Pressure switching valve Vacuum Switching Valve (VSV) may also be referred to as EVAP Pressure Switching Valve Vacuum Switching Valve (EVAP-PSVVSV).

Scheme 43

Vapor Pressure Sensor (ECHO)

Vapor pressure sensor and canister closed valve Vacuum Switching Valve (VSV) are used to determine if a leak or an abnormality exists in the EVAP system. (Scheme 43) Engine Control Module (ECM) determines if a leak or an abnormality exists in EVAP system by using input signal from vapor pressure sensor. Vapor pressure sensor may also referred to as EVAP vapor pressure sensor. Canister closed valve Vacuum Switching Valve (VSV) may also be referred to as EVAP Canister Closed Valve Vacuum Switching Valve (EVAP-CCVVSV).

Vapor Pressure Sensor (Land Cruiser, RAV4, Sienna, Tacoma, Tundra & 4Runner)

Vapor pressure sensor and vapor pressure sensor Vacuum Switching Valve (VSV) are used to determine if a leak or an abnormality exists in the EVAP system. (Scheme 44) Engine Control Module (ECM) determines if a leak or an abnormality exists in EVAP system by using input signal from vapor pressure sensor. 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).

Scheme 44

Variable Valve Timing (VVT) Sensor (Avalon)

See CAMSHAFT & CRANKSHAFT POSITION SENSORS (AVALON) .

Variable Valve Timing (VVT) Sensor (Celica, Corolla & ECHO)

See CAMSHAFT & CRANKSHAFT POSITION SENSORS (CELICA, COROLLA & ECHO) .

Vehicle Speed Sensor (Avalon, 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.

Vehicle Speed Sensor (Camry, Camry Solara, Celica, Corolla, ECHO, Land Cruiser, RAV4, Tacoma, Tundra & 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).

4WD Switch (Tacoma, Tundra 3.4L V6 & 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.

See ACOUSTIC CONTROL INDUCTION SYSTEM (ACIS) 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.

Canister Closed Valve Vacuum Switching Valve (CCVVSV)

See EVAPORATIVE EMISSION (EVAP) SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

Circuit Opening Relay

See FUEL DELIVERY under FUEL SYSTEM.

EGR Vacuum Switching Valve (VSV)

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

Electronically Controlled Transmission/Transaxle

See TRANSMISSION/TRANSAXLE CONTROLS under MISCELLANEOUS CONTROLS.

Electronic Spark Advance System

See DISTRIBUTORLESS IGNITION SYSTEM under IGNITION SYSTEM.

EVAP Vacuum Switching Valve (VSV)

See EVAPORATIVE EMISSION (EVAP) SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

Fuel Pump

See FUEL DELIVERY under FUEL SYSTEM.

Fuel Pressure Regulator Fuel Shutoff Valve

See FUEL DELIVERY under FUEL SYSTEM.

Fuel Pump Relay

See FUEL DELIVERY under FUEL SYSTEM.

Fuel Rail Fuel Shutoff Valve

See FUEL DELIVERY under FUEL SYSTEM.

Fuel Tank Fuel Shutoff Valve

See FUEL DELIVERY under FUEL SYSTEM.

HRT SUB1 Relay

See POSITIVE TEMPERATURE COEFFICIENT (PTC) HEATER under MISCELLANEOUS CONTROLS.

Idle Speed Control System

See IDLE SPEED under FUEL SYSTEM.

IG2 Relay

See IG2 RELAY under MISCELLANEOUS CONTROLS.

LOW FUEL LEVEL Warning Light

See FUEL LEAK DETECTION (CAMRY 2.2L 4-CYL. CNG MODELS) under FUEL CONTROL.

Pressure Switching Valve Vacuum Switching Valve

See EVAPORATIVE EMISSION (EVAP) SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

Self-Diagnostic System

See SELF-DIAGNOSTIC SYSTEMS .

Throttle Control Motor

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

Vapor Pressure Sensor Vacuum Switching Valve

See EVAPORATIVE EMISSION (EVAP) SYSTEM under EMISSION SYSTEMS & SUB-SYSTEMS.

Variable Valve Timing (VVT) Camshaft Timing Oil Control Valve

Variable Valve Timing (VVT) Camshaft Timing Oil Control Valve may also be referred to as oil control valve or VVT Oil Control Valve (OCV). See VARIABLE VALVE TIMING (VVT) SYSTEM under COMPUTERIZED ENGINE CONTROLS.

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.

A/F Heater Relay (Avalon, Camry 3.0L V6 Calif. Emission Vehicles, Camry Solara 3.0L V6 Calif. Emission Vehicles & Sienna Calif. Emission Vehicles)

A/F heater relay may also be referred to as A/F relay or A/F HTR relay. Constant battery voltage is supplied from battery, through A/F heater fuse to one side of A/F heater relay. A/F heater relay is energized by MREL terminal of Engine Control Module (ECM). When A/F heater relay is energized, 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 table.

A/F HEATER RELAY LOCATION

Scheme 45

Circuit Opening Relay (Avalon)

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 from ignition switch 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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

Circuit Opening Relay (Camry 2.2L 4-Cyl. CNG Models)

Circuit opening relay controls fuel supply 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 tank fuel shutoff valve and fuel pressure regulator fuel shutoff valve. For circuit opening relay location, see CIRCUIT OPENING RELAY LOCATION table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

Circuit Opening Relay (Camry 2.2L 4-Cyl. Gasoline Models, Camry 3.0L V6 & 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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

Circuit Opening Relay (Celica & ECHO)

Circuit opening relay controls fuel supply 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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

Circuit Opening Relay (Tundra 3.4L V6)

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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

Circuit Opening Relay (Tundra 4.7L V8)

Circuit opening relay controls fuel pump circuit by supplying voltage to fuel pump relay. 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 relay which supplies voltage to fuel pump for fuel pump operation. For circuit opening relay location, see CIRCUIT OPENING RELAY LOCATION table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article. For operation of fuel pump relay, see FUEL PUMP RELAY & FUEL PUMP RESISTOR .

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 table. Circuit opening relay may also be identified by appropriate illustration in appropriate SYSTEM & COMPONENT TESTING article.

CIRCUIT OPENING RELAY LOCATION (1)

EFI Main Relay (Avalon)

EFI main relay may also be referred to as EFI relay. EFI No. 1 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 table.

EFI Main Relay (Camry 2.2L 4-Cyl. CNG Models)

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 table.

EFI Main Relay (Camry 2.2L 4-Cyl. Gasoline Models & 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 table.

EFI Main Relay (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 table.

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. 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, EFI No. 1 and 2 fuses 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 table.

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 table.

EFI Main Relay (ECHO)

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. EFI main relay is then energized and provides battery voltage to circuit opening relay 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 table.

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. 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 +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 . For EFI main relay location, see EFI MAIN RELAY LOCATION table.

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 table.

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 table.

EFI Main Relay (Tacoma 2.4L 4-Cyl. & 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 Engine Control Module (ECM) when ignition is turned on. For EFI main relay location, see EFI MAIN RELAY LOCATION table.

EFI Main Relay (Tacoma 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. On Calif. emission vehicles, EFI main relay is energized by MREL terminal of Engine Control Module (ECM). On except Calif. emission vehicles, when ignition is turned on, voltage is supplied through IGN fuse to other side of EFI main relay and EFI main relay is then energized. On all models, 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 Engine Control Module (ECM) when ignition is turned on. For EFI main relay location, see EFI MAIN RELAY LOCATION table.

EFI Main Relay (Tundra 3.4L V6)

EFI main relay may also be referred to as EFI relay. EFI fuse No. 1 supplies constant battery voltage to one side of EFI main relay. On Calif. emission vehicles, EFI main relay is energized by MREL terminal of Engine Control Module (ECM). On except Calif. emission vehicles, when ignition is turned on, voltage is supplied through IGN fuse to other side of EFI main relay and EFI main relay is then energized. On all models, 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 table.

EFI Main Relay (Tundra 4.7L V8)

EFI main relay may also be referred to as EFI relay. EFI fuse No. 1 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, through EFI fuse No. 2, and to data link connector No. 1 and various other electrical components. EFI main relay also provides battery voltage to +B and +B1 terminals of ECM. For EFI main relay location, see EFI MAIN RELAY LOCATION table.

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 table.

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 table.

EFI MAIN RELAY LOCATION

Fuel Manual Shutoff Valve & Fuel Filter Assembly (Camry 2.2L 4-Cyl. CNG Models)

Fuel manual shutoff valve can be used to shut off fuel supply from the fuel tank if a gas leak exists or when performing service procedures. Fuel manual shutoff valve is located near driver's side rear tire, underneath the vehicle, near fuel lines just below fuel tank behind the rear seat. (Scheme 46) Rotating handle on fuel manual shutoff valve clockwise 90 degrees will close the valve and rotating the handle counterclockwise 90 degrees will open the valve.

Fuel filter assembly for CNG system is located below vehicle floor, next to fuel manual shutoff valve. (Scheme 46) Fuel filter assembly consists of a fuel filter body, fuel filter housing, fuel filter element and drain plug. (Scheme 46) Fuel filter element is located inside fuel filter housing and can be changed. Drain plug may be removed to allow water and oil to be drained from fuel filter assembly.

Scheme 46

Fuel Pump (Avalon, Camry 2.2L 4-Cyl. Gasoline Models, Camry 3.0L V6, Camry Solara, Celica, Corolla, ECHO, RAV4, Sienna, Tacoma, Tundra 3.4L V6 & 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 (Tundra 4.7L V8)

Electric fuel pump is mounted in fuel tank. Fuel pump operating speed is controlled by operating condition of the engine such as: starting, idling, light load or heavy load by use of fuel pump resistor and fuel pump relay. For operation of fuel pump relay and fuel pump resistor, see FUEL PUMP RELAY & FUEL PUMP RESISTOR .

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

Fuel pump operating speed is controlled by engine operating conditions 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. When engine starts, or engine is under heavy load at high speeds, ECM delivers input signal of about 3.8 volts to fuel pump ECU. Fuel pump ECU then delivers about battery voltage to fuel pump and fuel pump operates at high speed. When engine is under heavy load at low speeds, ECM delivers an input signal of about 2.5 volts to fuel pump ECU. Fuel pump ECU then delivers about 10 volts to fuel pump and fuel pump operates at medium speed. When engine is idling or under light loads, ECM delivers an input signal of about 1.3 volts to fuel pump ECU. Fuel pump ECU then delivers about 8.5 volts to fuel pump and fuel pump operates at low speed. If a problem exists in fuel pump ECU or control circuit, Diagnostic Trouble Code (DTC) P1200 may be stored in ECM. See SELF-DIAGNOSTIC SYSTEM in 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 47)

Scheme 47

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 48) Fuel pump switch contains a reset switch which has an OFF and ON position. (Scheme 48) 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 48

Fuel Pump Relay & Fuel Pump Resistor (Tundra 4.7L V8)

Fuel pump operating speed is controlled by operating condition of the engine such as: starting, idling, light load or heavy load. When engine is cranking and start signal is received at Engine Control Module (ECM), the ECM energizes circuit opening relay and voltage is applied to both sides of fuel pump relay. Fuel pump relay contacts are closed to one side and voltage is applied directly to fuel pump in which fuel pump operates at high speed. After engine starts during idling or light loads, fuel pump relay is energized by FPR terminal of ECM and contacts in fuel pump relay close to other side of relay. Voltage is then supplied to fuel pump by going from fuel pump relay through fuel pump resistor. Fuel pump now operates at low speed. Fuel pump relay is located in fuse/relay box at driver's side front corner of engine compartment, next to battery. Fuel pump resistor is located at driver's side front corner of engine compartment, near end of fuse/relay box. (Scheme 49)

Scheme 49

Fuel Pressure Regulator (Avalon, Camry 2.2L 4-Cyl. Gasoline Models, Camry 3.0L V6, Camry Solara, Celica, Corolla, ECHO, 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 (Camry 2.2L 4-Cyl. CNG Models)

Fuel pressure regulator is used to regulate fuel pressure from fuel tank to the fuel injectors at 114 psi (8.0 kg/cm 2 ). Fuel pressure regulator is located in fuel line between fuel tank and fuel rail, just below brake booster. (Scheme 41) An oil separator is used to trap moisture and oil in the fuel on low-pressure side of the fuel system between fuel pressure regulator and fuel rail. Oil separator is located on bottom of fuel pressure regulator. (Scheme 41) A relief valve is incorporated into fuel pressure regulator and is used to protect fuel system components on low-pressure side of the system between fuel pressure regulator and fuel rail.

Fuel pressure regulator contains a coolant passage which allows engine coolant to flow through the fuel pressure regulator. Engine coolant is used to warm fuel pressure regulator to prevent damage to any rubber components, as fuel pressure regulator becomes excessively cold while reducing the fuel pressure.

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

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 pressure regulator is mounted on the fuel rail.

Fuel Pressure Regulator Fuel Shutoff Valve (Camry 2.2L 4-Cyl. CNG Models)

Fuel pressure regulator fuel shutoff valve is controlled by Engine Control Module (ECM). ECM uses fuel pressure regulator fuel shutoff valve to shut off fuel supply at fuel inlet side of fuel pressure regulator when ignition is off, engine stalls, air bag is deployed, or fuel pressure in the fuel pipe becomes abnormally low. Fuel pressure regulator fuel shutoff valve may also be referred to as fuel shutoff valve (fuel pressure regulator). Fuel pressure regulator fuel shutoff valve is located on fuel pressure regulator located in fuel line between fuel tank and fuel rail, just below brake booster. (Scheme 41)

Fuel Rail Fuel Shutoff Valve (Camry 2.2L 4-Cyl. CNG Models)

Fuel rail fuel shutoff valve is controlled by Engine Control Module (ECM). ECM uses fuel rail fuel shutoff valve to shut off fuel supply at fuel rail when ignition is off, engine stalls, air bag is deployed, or fuel pressure in the fuel pipe becomes abnormally low. Fuel rail fuel shutoff valve may also be referred to as delivery pipe fuel shutoff valve or fuel shutoff valve (delivery pipe). Fuel rail fuel shutoff valve is located at end of fuel rail at flywheel end of engine and contains a Blue 2-pin electrical connector.

Fuel Tank Fuel Shutoff Valve (Camry 2.2L 4-Cyl. CNG Models)

Fuel tank fuel shutoff valve is controlled by Engine Control Module (ECM). ECM uses fuel tank fuel shutoff valve to shut off fuel supply at fuel tank when ignition is off, engine stalls, air bag is deployed, or fuel pressure in the fuel pipe becomes abnormally low. Fuel tank fuel shutoff valve may also be referred to as shutoff valve (fuel tank). Fuel tank fuel shutoff valve is located on fuel tank valve assembly at end of fuel tank behind the rear seat. (Scheme 42)

Fuel Tank Valve Assembly (Camry 2.2L 4-Cyl. CNG Models)

Fuel tank valve assembly is located at end of fuel tank behind rear seat. (Scheme 42) Fuel tank valve assembly contains fuel tank fuel shutoff valve, inlet check valve and relief valve.

Inlet check valve is used to prevent fuel leakage and is connected to the filler pipe. Inlet check valve remains closed by spring pressure and pressure of the gas in the fuel tank. When filling fuel tank, inlet check valve opens by pressure of incoming gas and then closes when filling is complete.

Relief valve is used to prevent damage to fuel tank by releasing excessive fuel pressure from fuel tank if fuel tank is exposed to abnormally hot temperatures. When fuel tank is exposed to abnormally hot temperatures, relief valve opens at specified temperature by melting, allowing excessive fuel pressure to be released by discharging gas through vent tube to the outside of the vehicle to prevent fuel tank from bursting.

IG2 Relay (Avalon, Celica & RAV4)

See IG2 RELAY under MISCELLANEOUS CONTROLS.

Fuel Clearing Control (Camry 2.2L 4-Cyl. CNG Models)

After vehicle is driven at speeds greater than approximately 38 MPH and ignition is turned off after Engine Control Module (ECM) has detected intake air temperature is less than 77°F (25°C), ECM closes fuel rail fuel shutoff valve. Engine will not stop immediately, as fuel clearing control allows engine to stop after fuel in fuel rail has been used. If engine remains running for more than 2 seconds after ignition is turned off, EFI main relay will be turned off to stop the engine.

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.

Fuel Injector Unsticking Control (Camry 2.2L 4-Cyl. CNG Models)

When ignition is turned on after fuel clearing control was performed, fuel injector unsticking control activates 2 fuel injectors at one time to free the valve in the fuel injector that is stuck to the valve seat. At low temperature conditions, fuel rail fuel shutoff valve remains closed so fuel injectors will not inject fuel. This prevents fuel injector from sticking and ensures engine starts at low temperature conditions.

Fuel Leak Detection (Camry 2.2L 4-Cyl. CNG Models)

If Engine Control Module (ECM) detects a gas leak through signals received from fuel rail fuel pressure sensor and fuel pipe fuel pressure sensor, ECM performs fuel leak detection and closes fuel tank fuel shutoff valve, fuel rail fuel shutoff valve and fuel pressure regulator fuel shutoff valve. ECM also flashes LOW FUEL LEVEL warning light on instrument panel at one second intervals to warn the operator. LOW FUEL LEVEL warning light is located on instrument panel near bottom of fuel gauge. LOW FUEL LEVEL warning light may also flash if a low fuel condition exists. If a low fuel condition exists, this display is different than display for a fuel leak detection, as LOW FUEL LEVEL warning light will be off for 2 seconds and then come on for one second with a 2 second pause between the flashes.

Fuel leak detection may be reset by disconnecting negative battery cable momentarily and then reconnecting negative battery cable. This should enable engine to start.

A/C-Cut Control System (Camry 2.2L 4-Cyl. CNG & Gasoline Models, Camry Solara 2.2L 4-Cyl., Celica, Corolla, ECHO & 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, ECHO, RAV4, Sienna, Tacoma, Tundra 3.4L V6 & 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 & Tundra 4.7L V8)

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

Throttle Opener (Avalon, Camry, Camry Solara, RAV4, Sienna, Tacoma, Tundra 3.4L V6 & 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 also 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 2 camshaft position sensors and crankshaft position sensor. Camshaft position sensors may also be referred to as Variable Valve Timing (VVT) sensors. Camshaft position sensors and crankshaft position sensor deliver input signals to ECM. ECM detects standard crankshaft position based on input signals from camshaft position sensors and actual crankshaft position, and engine speed by crankshaft position sensor input signals. Camshaft position sensors are located at flywheel end of each cylinder head, just below valve cover. (Scheme 5) Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. (Scheme 5) For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

The ECM uses 6 ignition primary control signals to the ignitors for the ignition coils. DIS uses 6 ignition coils with internal ignitors, one ignition coil for each cylinder. (Scheme 50) 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. ECM monitors IGF circuit at ignitor to ensure ignition coils have fired.

Note. IG2 relay provides voltage to ignition coils. For additional information on IG2 relay, see IG2 RELAY under MISCELLANEOUS CONTROLS.

Scheme 50

Camry 2.2L 4-Cyl. CNG & Gasoline Models, Camry Solara 2.2L 4-Cyl. & 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 camshaft position sensor and crankshaft 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 timing belt end of cylinder head, on firewall side of engine. (Scheme 6), (Scheme 7) and (Scheme 13). Crankshaft position sensor is located behind lower timing belt cover, near crankshaft sprocket. (Scheme 6), (Scheme 7) and (Scheme 13). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

The ECM uses 2 ignition primary control signals to ignitor for ignition coils. DIS uses 2 ignition coils with internal ignitors to fire 2 cylinders simultaneously using same ignition coil. (Scheme 51) Cylinders No. 1 and 4 fire together and cylinders No. 2 and 3 fire together. Cylinder No. 1 is front cylinder at timing belt 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.

Note. On Camry 2.2L CNG models, INJ relay provides voltage to ignition coils. For additional information on INJ relay, see INJ RELAY under MISCELLANEOUS CONTROLS.

Note. On RAV4, IG2 relay provides voltage to ignition coils. For additional information on IG2 relay, see IG2 RELAY under MISCELLANEOUS CONTROLS.

Scheme 51

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 camshaft position sensor and crankshaft 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 8)and (Scheme 14). Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. (Scheme 8)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. DIS uses 3 ignition coils which fire 2 cylinders simultaneously using same ignition coil. (Scheme 52) 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 52

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 camshaft position sensor and crankshaft position sensor. Camshaft position sensor may also be referred to as Variable Valve Timing (VVT) 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 Celica and Corolla, camshaft position sensor is located just above intake manifold on cylinder head, at flywheel end of engine. (Scheme 9)and (Scheme 10). On ECHO, camshaft position sensor is located on end of cylinder head at flywheel end of engine. (Scheme 11) On all models, crankshaft position sensor is located on front of engine, near crankshaft pulley. (Scheme 9)- (Scheme 11). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

ECM uses 4 ignition primary control signals to ignitors for ignition coils. DIS uses 4 ignition coils with internal ignitors, one ignition coil for each cylinder. (Scheme 53) Cylinder No. 1 is front cylinder at timing chain end of engine and cylinder No. 4 is rear cylinder at flywheel end of engine. ECM monitors IGF circuit at ignitor to ensure ignition coils have fired.

Note. On Celica, IG2 relay provides voltage to ignition coils. For additional information on IG2 relay, see IG2 RELAY under MISCELLANEOUS CONTROLS.

Scheme 53

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 camshaft position sensor and crankshaft 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 12)and (Scheme 18). Crankshaft position sensor is located at front of crankshaft, near crankshaft pulley. (Scheme 12)and (Scheme 18). 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 54) 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 54

Tacoma 2.4L 4-Cyl. Calif. Emission Vehicles, Tacoma 2.7L 4-Cyl. Calif. Emission Vehicles & 4Runner 2.7L 4-Cyl. Calif. Emission Vehicles

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 camshaft position sensor and crankshaft 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 15)and (Scheme 19). Crankshaft position sensor is located near crankshaft pulley, just above oil pan on driver's side of engine. (Scheme 15)and (Scheme 19). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.

ECM uses 4 ignition primary control signals to ignitors for ignition coils. DIS uses 4 ignition coils with internal ignitors, one ignition coil for each cylinder. (Scheme 53) Cylinder No. 1 is front cylinder at timing chain end of engine and cylinder No. 4 is rear cylinder at flywheel end of engine. ECM monitors IGF circuit at ignitor to ensure ignition coils have fired.

Tacoma 2.4L 4-Cyl. Except Calif. Emission Vehicles, Tacoma 2.7L 4-Cyl. Except Calif. Emission Vehicles & 4Runner 2.7L 4-Cyl. Except Calif. Emission Vehicles

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 camshaft position sensor and crankshaft 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 15)and (Scheme 19). Crankshaft position sensor is located near crankshaft pulley, just above oil pan on driver's side of engine. (Scheme 15)and (Scheme 19). 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 51) 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, Tundra 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 camshaft and crankshaft 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 16), (Scheme 17) and (Scheme 20). Crankshaft position sensor is located at front of engine, just above crankshaft pulley. (Scheme 16), (Scheme 17) and (Scheme 20). For knock sensor location, see REMOVAL, OVERHAUL & INSTALLATION - V6 & V8 article.

ECM uses 3 ignition primary control signals to ignitor for ignition coils. (Scheme 55) 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 55

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 56) Amount of EGR operation is regulated by EGR vacuum modulator according to engine load. EGR valve operation is controlled by EGR VSV which is controlled by Engine Control Module (ECM). If ECM turns on EGR VSV, this causes EGR valve to close and shuts off the exhaust gas. ECM may shut off EGR system if any of the following conditions exist.

1. Engine Is Not At Normal Operating Temperature
2. During Deceleration With Throttle Closed
3. During Light Or Heavy Engine Load
4. Engine Is Idling
5. Engine Speed Is Greater Than 4400 RPM

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 56

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 position sensor, vacuum tank, EGR Vacuum Switching Valve (VSV) and EGR Vacuum Control Valve (VCV). (Scheme 57) An EGR gas temperature sensor is screwed into lower side of EGR valve.

Amount of EGR operation is regulated by the vacuum which is regulated by EGR VSV which is controlled 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 may shut off EGR system if any of the following conditions exist.

1. Engine Is Not At Normal Operating Temperature
2. During Deceleration With Throttle Closed
3. During Light Engine Load
4. Engine Is Idling
5. Engine Speed Is Greater Than 4400 RPM

The ECM uses various input signals for controlling EGR system operation. For EGR system and component testing, see SYSTEM & COMPONENT TESTING - V6 & V8 article.

Scheme 57

Tacoma 2.4L 4-Cyl. 2RZ-FE Except Calif. Emission Vehicles, Tacoma 2.7L 4-Cyl. 3RZ-FE & 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 58) Amount of EGR operation is regulated by EGR vacuum modulator according to engine load. EGR valve operation is controlled by EGR VSV, which is controlled by Engine Control Module (ECM). If ECM turns on EGR VSV, this causes EGR valve to close and shut off the exhaust gas. ECM may turn on EGR VSV if any of the following exist.

1. Engine Is Not At Normal Operating Temperature
2. During Deceleration With Throttle Closed
3. During Light Engine Load
4. Engine Is At High Speed

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 58

EVAPORATIVE EMISSION (EVAP) SYSTEM

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

Avalon, Camry 2.2L 4-Cyl. Gasoline Models, Camry 3.0L V6, Camry Solara, Celica & Corolla

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. Vapor pressure sensor, pressure switching valve Vacuum Switching Valve (VSV) and canister closed valve Vacuum Switching Valve (VSV) are used to determine if a leak or an abnormality exists in EVAP system. (Scheme 43) Engine Control Module (ECM) determines if a leak or an abnormality exists in EVAP system by using input signal from vapor pressure sensor. Vapor pressure sensor may also referred to as EVAP vapor pressure sensor. Canister closed valve Vacuum Switching Valve (VSV) may also be referred to as EVAP Canister Closed Valve Vacuum Switching Valve (EVAP-CCVVSV). Pressure switching valve Vacuum Switching Valve (VSV) may also be referred to as EVAP Pressure Switching Valve Vacuum Switching Valve (EVAP-PSVVSV). If a leak or an abnormality exists in EVAP system, a Diagnostic Trouble Code (DTC) will be stored in ECM. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs. 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.

ECHO

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. Vapor pressure sensor and canister closed valve Vacuum Switching Valve (VSV) are used to determine if a leak or an abnormality exists in EVAP system. (Scheme 43) Engine Control Module (ECM) determines if a leak or an abnormality exists in EVAP system by using input signal from vapor pressure sensor. Vapor pressure sensor may also referred to as EVAP vapor pressure sensor. Canister closed valve Vacuum Switching Valve (VSV) may also be referred to as EVAP Canister Closed Valve Vacuum Switching Valve (EVAP-CCVVSV). If a leak or an abnormality exists in EVAP system, a Diagnostic Trouble Code (DTC) will be stored in ECM. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs. 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.

Land Cruiser, RAV4, Sienna, Tacoma, Tundra & 4Runner

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. Vapor pressure sensor and vapor pressure sensor Vacuum Switching Valve (VSV) are used to determine if a leak or an abnormality exists in EVAP system. (Scheme 44) Engine Control Module (ECM) determines if a leak or an abnormality exists in EVAP system by using input signal from vapor pressure sensor. 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). If a leak or an abnormality exists in EVAP system, a Diagnostic Trouble Code (DTC) will be stored in ECM. See SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs. 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.

Avalon, Camry 2.2L 4-Cyl. Gasoline Models, Camry 3.0L V6, Camry Solara, Celica, Corolla & ECHO

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 59)

When fuel tank cap is removed, atmospheric pressure is applied to port "A" on overfill check valve. (Scheme 60) Overfill check valve may also be referred to as ORVR-OCKV, fuel tank overfill check valve 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 59

Scheme 60

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.

SELF-DIAGNOSTIC SYSTEMS

Engine Control Module (ECM) is equipped with self-diagnostic system. By analyzing various input signals, ECM detects system malfunctions related to various operating parameters. When malfunction occurs, ECM may inform the driver by turning on Malfunction Indicator Light (MIL) on the instrument panel.

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

Diagnostic Trouble Codes (DTC) may be set by malfunction of various engine sensors, switches or circuits. DTC is stored in ECM memory. When DTC is stored, MIL on instrument panel will come on. DTC can be retrieved for system diagnosis. For additional information on self-diagnostic system, see SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article for retrieving and servicing of DTCs.

MISCELLANEOUS CONTROLS

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

Note. IG2 relay may also be referred to as ignition relay.

IG2 fuse supplies constant battery voltage to one side of IG2 relay. When ignition is turned on, voltage is supplied from ignition switch to other side of IG2 relay and IG2 relay is then energized. When IG2 relay is energized, IG2 relay provides battery voltage to fuel injectors and ignition coils. IG2 relay is located in fuse/relay box at driver's side front corner of engine compartment, near battery and air cleaner.

IG2 fuse supplies constant battery voltage to one side of IG2 relay. When ignition is turned on, voltage is supplied from ignition switch to other side of IG2 relay and IG2 relay is then energized. When IG2 relay is energized, IG2 relay provides battery voltage to fuel injectors and ignition coils. IG2 relay is located in fuse/relay box at driver's side front corner of engine compartment, just in front of strut tower, near battery.

RAV4

IG2 relay may also be referred to as ignition relay. IGN fuse supplies constant battery voltage to one side of IG2 relay. When ignition is turned on, voltage is supplied from ignition switch to other side of IG2 relay and IG2 relay is then energized. When IG2 relay is energized, IG2 relay provides battery voltage to fuel injectors and ignition coils. IG2 relay is located in relay box at driver's side front corner of engine compartment, just in front of strut tower.

Camry 2.2L 4-Cyl. CNG Models

INJ fuse supplies constant battery voltage to one side of INJ relay. INJ relay is energized by MREL terminal of Engine Control Module (ECM). When INJ relay is energized, INJ relay provides battery voltage to ignition coils and +B1 terminal at ECM. INJ relay is located in fuse/relay box at driver's side front corner of engine compartment, just in front of the battery.

PTC heater is a small electrical heater located in the heater core and is used on vehicles equipped for cold areas. (Scheme 61) PTC heater may be turned on if all of the following conditions exist: temperature control switch is at MAX HOT position, engine speed is more than 1050 RPM, engine coolant temperature is less than 176°F (80°C) and generator power ratio is less than 95 percent. PTC heater may also be turned on and off depending on generator power ratio.

Temperature control switch operates a maximum hot switch which provides an input signal to Engine Control Module (ECM) for controlling PTC heater operation. Maximum hot switch may also be referred to as MAX HOT switch.

HTR SUB1 relay is used for supplying battery voltage to PTC heater. HTR SUB1 relay may also be referred to as heater sub relay. HTR SUB1 fuse supplies battery voltage to one side of HTR SUB1 relay. When ignition is turned on, voltage is supplied from ignition switch, through ECU-IG fuse and to other side of HTR SUB1 relay. When PTC amplifier completes ground circuit for HTR SUB1 relay, HTR SUB1 relay then provides battery voltage to PTC heater for PTC heater operation. HTR SUB1 relay is located in fuse/relay box at driver's side front corner of engine compartment, just in front of strut tower, near battery.

Scheme 61

TRANSMISSION/TRANSAXLE CONTROLS

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

Electronically Controlled Transmission/Transaxle (ECT)

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

See also:
• ENGINE IMMOBILIZER SYSTEM AVAILABILITY
• INPUT DEVICES
• OUTPUT SIGNALS
• SELF-DIAGNOSTIC SYSTEMS
• ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS)
• INTAKE AIR TEMPERATURE SENSOR
• CAMSHAFT & CRANKSHAFT POSITION SENSORS (AVALON)
• CAMSHAFT & CRANKSHAFT POSITION SENSORS (CELICA, COROLLA & ECHO)
• ACOUSTIC CONTROL INDUCTION SYSTEM (ACIS)
• FUEL DELIVERY
• EVAPORATIVE EMISSION (EVAP) SYSTEM
• TRANSMISSION/TRANSAXLE CONTROLS
• DISTRIBUTORLESS IGNITION SYSTEM
• FUEL LEAK DETECTION (CAMRY 2.2L 4-CYL. CNG MODELS)
• VARIABLE VALVE TIMING (VVT) SYSTEM
• FUEL PUMP RELAY & FUEL PUMP RESISTOR
• FUEL PUMP ELECTRONIC CONTROL UNIT (ECU) & FUEL PUMP SWITCH