Procedures to Retrieve Trouble Codes

Toyota Odb1 Codes

There are several different types and locations of diagnostic connectors which are used to trigger and, in some cases, read diagnostic code output from Toyota EFI engines. All late model TCCS applications, from 1988, use a multiple terminal diagnostic check connector. Earlier models use this same multiple terminal or a two-terminal check connector, all located under the hood. The procedure to examine the ECU memory for diagnostic codes is typically very simple regardless of which vintage engine...

Inspect and Adjust the Shift Cable

To inspect the shift cable, move the gear selector from neutral to each position. The gear selector should move smoothly and accurately to each gear position. Adjust the shift cable in the indicator does not line-up with the position indicator while in the proper detent. To adjust, loosen the swivel nut on the shift linkage. Push the manual lever at the transmission fully toward the torque converter end of the transmission. Then pull the lever back two notches from Park through Reverse to the...

Fuel Pressure and Volume Testing

Tester Pressure Fuel Toyota Prius

Safety Tips Prior to installing a fuel pressure gauge and checking fuel pressure, residual pressure must be safely relieved to reduce the hazard of fire when the fuel line is opened. It is advisable to have a fire extinguisher whenever opening the fuel system. Common gauge hookup locations are at the fuel rail, fuel filter, or the cold start valve using SST 09268-45012 and 09268-45013-01. Repair manual procedures should always be followed. Whenever a fuel hose connection secured with a copper...

OnOff Control Vacuum Switching Valve VISC System

Vacuum Switch Valve Corolla

The simple On-Off Vacuum Switching Valve VSV ISC system is controlled by signals from the ECU or directly by tail lamp and rear window defogger circuits. The Vacuum Switching Valve VSV is typically located on the engine often under the intake manifold or in the engine compartment, controlling a fixed air bleed into the intake manifold. The valve is a normally closed N Q design which is opened when current is passed through the solenoid windings. Unlike most ECU controlled circuits which are...

Karman Vortex Air Flow Meter Operation

Karman Vortex Air Flow Sensor

Intake air flow reacting against the vortex generator creates a swirling effect to the air downstream, very similar to the wake created in the water after a boat passes. This wake or flutter is referred to as a Karman Vortex. The frequencies of the vortices vary in proportion to the intake air velocity engine load . The vortices are metered into a pressure directing hole from which they act upon the metal foil mirror. The air flow against the mirror causes it to oscillate in proportion to the...

Throttle Position Sensor

Rav4 Throttle Position Sensor Measure

The TPS is mounted on the throttle body and converts the throttle valve angle into an electrical signal. As the throttle opens, the signal voltage increases. The ECM uses throttle valve position information to know engine mode idle, part throttle, wide open throttle. switch off AC and emission controls at Wide Open Throttle WOT . The basic TPS requires three wires. Five volts are supplied to the TPS from the VC terminal of the ECM. The TPS voltage signal is supplied to the VTA terminal. A...

Shift Lock Override Button

In order to move the shift lever out of Park, the ignition switch must be in the Accessory or ON position and the brake pedal must be depressed. When the brake pedal is depressed, the ECU turns on the solenoid, moving the plate stopper and allowing the shift lock plate to move down with the grooved pin. If the shift lock solenoid becomes inoperative, the shift lever cannot be moved and the vehicle cannot be moved. The shift lock override button can be used to release the plate stopper from the...

ECU Grounds and Quick Checks

Drawing Corolla 4efe E11

No electrical circuit will function normally without a dependable ground. Toyota EFI systems use a redundant ground system which significantly reduces the chance of ground problems however, this circuit should never be overlooked when troubleshooting ECU related systems. The E2 circuit serves as a signal return or sensor ground. Referring to an EWD, you will notice that the throttle position sensor, water and air temperature sensors, and air flow meter all flow current to ground through circuit...

Vapor Pressure Sensor

Evaporation Pressure Sensor Code 193

The Vapor Pressure Sensor (VPS) measures the vapor pressure in the evaporative emission control system. The Vapor Pressure Sensor may be located on the fuel tank, near the charcoal canister assembly, or in a remote location. This sensor uses a silicon chip with a calibrated reference pressure on one side of the chip, the other side of the chip is exposed to vapor pressure. Changes in vapor pressure cause the chip to flex and vary the voltage signal to the ECM. The voltage signal out depends on...

NE Signal and G Signal

What Signal

Though there are different types of ignition systems, the use of the NE and G signals is consistent. The NE signal indicates crankshaft position and engine RPM. The G signal also called VVT signal provides cylinder identification. By comparing the G signal to the NE signal, the ECM is able to identify the cylinder on compression. This is necessary to calculate crankshaft angle initial ignition timing angle , identify which coil to trigger on Direct Ignition System independent ignition , and...

Injector Maintenance and Cleaning

Spray Patterns Fuel Injectors

Although it is not the problem it was back in the early to mid '80s, fuel injector restriction is still an issue which needs to be addressed from both a preventative maintenance and repair viewpoint. The best method of injector maintenance is continuous use of high quality fuels with a level of detergency adequate to keep the injector nozzles clean. It is also prudent to offer injector cleaning service using the Toyota approved injector cleaning system and solvents. This service can be offered...

Intake Air Temperature IAT Sensor

Iat Sencor Toyota Corola

The IAT detects the temperature of the incoming air stream. On vehicles equipped with a MAP sensor, the IAT is located in an intake air passage. On Mass Air Flow sensor equipped vehicles, the IAT is part of the MAF sensor. The IAT is connected to the THA terminal on the ECM. The IAT is used for detecting ambient temperature on a cold start and intake air temperature as the engine heats up the incoming air. NOTE One strategy the ECM uses to determine a cold engine start is by comparing the ECT...

Air Conditioning Idleup

Daewoo Matiz Idle Valve Location

The air conditioning idle-up system is used to increase engine idle rpm any time the air conditioning compressor is in operation. The system shown is used on D type EFI applications where the ECU controlled Idle Speed Control Valve ISCV does not have an A C idle-up feature. This system maintains engine idle stability during periods of A C compressor operation. Additionally, it keeps compressor speed sufficiently high to ensure adequate cooling capacity at idle speed. The A C idle-up system...

Injector Driver Circuits

Efi Injector Drive Circuits

Current is supplied to the ECU driver circuits 10 and 20 in example through the fuel injectors. Current flows either directly from the ignition switch or from the EFI Main Relay. When the ECU driver circuit turns on, current flows to ground through the injector solenoid coil. The magnetic field created causes the injector to open against spring tension. When the ECU driver circuit turns off, the spring closes the injector valve. There are two common types of driver circuits currently in use on...

Karman Vortex Air Flow Meter Terminal Identification

Air Flow Sensor Karman Vortex

Digital frequency signal representing air flow The Karman vortex air flow meter and ECU are wired as shown in the diagram. Signal characteristics are represented by the illustration of the variable frequency square wave. Because of the pull-up resistor wired between the Vcc and Ks circuit, the Ks signal will go to 5 volts if the circuit is opened. When air passes through the air flow meter, the vortex generator creates a swirling of the air downstream. This swirling effect is referred to as a...

Toyota Camry Electrical Wiring Diagram

Toyota Wiring Diagrams Color Code

INTRODUCTION A HOW TO USE THIS MANUAL B TROUBLESHOOTING C ABBREVIATIONS D GLOSSARY OF TERMS AND SYMBOLS E RELAY LOCATIONS F ELECTRICAL WIRING ROUTING G POWER SOURCE Current Flow Chart H ABS ANTI-LOCK BRAKE SYSTEM AIR CONDITIONING PUSH CONTROL SW TYPE . AIR CONDITIONING LEVER CONTROL SW TYPE AUTO ANTENNA S D AUTO ANTENNA W G BACK DOOR LOCK W G w o POWER WINDOW BACK-UP LIGHT CHARGING CIGARETTE LIGHTER AND CLOCK COMBINATION METER CRUISE CONTROL DOOR AND AT INDICATOR 3VZ-FE AND A T INDICATOR 5S-FE...

Throttle Position Sensor Signal

Toyota Camry Throttle Position Sensor

In order to determine if the throttle position sensor signal and brake switch signal are being received by the ECU, place the ignition switch to the ON position with the engine off, connect a digital voltmeter to the diagnostic check connector and slowly depress the throttle. On models prior to 1987, if the vehicle does not have a diagnostic check connector in the engine compartment, connect the voltmeter to the DG Terminal. Its location can be found in the appropriate repair manual. The ECT...

Decel Dashpot and Throttle Opener Systems

Dise Milinos Azteca

A decel dashpot or throttle opener is mounted to the throttle body on some engines. The decel dashpot is designed to keep the throttle valve from closing too suddenly during deceleration. The throttle opener is designed to hold the throttle valve open slightly after the engine is turned off. Non ECU Controlled Throttle Opener Starting with 1990 3S-FE and 5S-FE engines, a simple throttle opener diaphragm was added to the throttle body. The throttle opener diaphragm is spring loaded in the...

OBD OnBoard Diagnostic System Generation

Toyota Engine Diagnostic Receipt

In April 1985, the California Air Resources Board CARB approved On-Board Diagnostic system regulations, referred to as OBD. These regulations, which apply to almost all 1988 and newer cars and light trucks marketed in the State of California, require that the engine control module ECM monitor critical emission related components for proper operation and illuminate a malfunction indicator lamp MIL on the instrument panel when a malfunction is detected. The OBD system also provides for a system...

Step Motor Type ISC Valve

Isc Stepper Motor

The Step Motor type ISCV is located on the intake air chamber or throttle body. It regulates engine speed by means of a stepper motor and pintle valve which controls the volume of air by-passing the closed throttle valve. The ISCv throttle air by-pass circuit routes intake air past the throttle valve directly to the intake manifold through a variable opening between the pintle valve and its seat. The valve assembly consists of four electrical stator coils, a magnetic rotor, a valve and valve...

The Air Induction System

Type Efi Air Flow System Diagrams

The air induction system consists of the air cleaner, air flow meter, throttle valve, air intake chamber, intake manifold runner, and intake valve. Air delivered to the engine is a function of driver demand. As the throttle valve is opened further, more air is allowed to enter the engine cylinders. When the throttle valve is opened, air flows through the air cleaner, through the air flow meter (on L type systems), past the throttle valve, and through a well tuned intake manifold runner to the...

The Obdii Diagnostic Circuit

Obd Scan Tool Diagram

The OBD-II data line is a bi-directional communication link which is capable of transmitting and receiving data. This feature allows the Diagnostic Tester to operate system actuators and send commands to the ECM in addition to displaying system data. The high speed OBD-II data stream typically consists of 50 to 75 data words representing virtually all sensor inputs, actuator outputs, several calculated parameters, many fuel feedback related parameters, and cylinder misfire data. The data is...

The OBD Diagnostic Circuit

2002 Toyota 4runner Dlc Terminal

This unidirectional data stream typically consists of 14 to 20 data words representing primarily sensor inputs and three outputs injection pulse width, spark advance angle, and idle speed control command. Data is transmitted at a rate of 100 baud, updating on the Diagnostic Tester display approximately once every 1.25 seconds. Depending on application, the data is accessed from either DLC 1 or DLC 2. Data is triggered by grounding the TE2 circuit and reading the VF1 circuit. Diagnostic Trouble...

Engine Cranking Signal STA

What Mean Ecu

The STA signal is used by the ECU to allow additional air to enter the intake manifold while cranking the engine. Additionally, it is used to determine when to enrich injection for starting and when to operate the Fuel Pressure-Up (FPU) system. In the event that the STA signal malfunctions, the engine may be difficult to start. The STA signal at the ECU will be low at all times except while the engine is cranking. While cranking, the STA signal goes high (cranking voltage) as current flows...

Learned Idle Speed Control

Idle Control Valve Toyota Yaris

The idle speed control program is based on an ECU stored look up table which lists pintle step positions in relation to specific engine rpm values. Over time, engine wear and other variations tend to change these relationships. Because this system is capable of feedback control, it is also capable of memorizing changes in the relationship of step position and engine rpm. The ECU periodically rewrites the look up table to provide more rapid and accurate response to changes in engine rpm. The...

Electronic Control System

The electronic control system consists of various engine sensors, Electronic Control Unit (ECU), fuel injector assemblies, and related wiring. The ECU determines precisely how much fuel needs to be delivered by the injector by monitoring the engine sensors. The ECU turns the injectors on for a precise amount of time, referred to as injection pulse width or injection duration, to deliver the proper air fuel ratio to the engine.

Electrical Load Sensor ELS

Strategic Layout Hospitals

The ELS circuit signals the ECU when significant electrical load has been placed on the charging system from the vehicle lighting or rear window defogger systems. The ECU uses this information to increase the duty cycle ratio on the Rotary ISC Valve, thereby maintaining a stable idle speed. The ELS signal at the ECU will be low as long as the tail lamps and rear window defogger are off. When either of these accessories are turned on, current flows to the accessory and through an isolation diode...

Displaying Engine Data

Toyota Tdcl

The type of serial data available depends on the vehicle you are working on. Many Toyota vehicles with OBD, manufactured since 1989, have a serial data stream available on the VF1 terminal of DLC 1 Check connector or the ENG terminal of DLC 2 TDCL . Vehicles which support a serial data stream can be identified by the presence of a TE2 circuit see the application matrix on page 86 of this handbook . Depending on the vehicle, there can be as many as 20 different sensor, actuator, and diagnostic...

Manifold Absolute Pressure MAP Sensor

Absolute Pressure

In the Manifold Absolute Pressure MAP sensor there is a silicon chip mounted inside a reference chamber. On one side of the chip is a reference pressure. This reference pressure is either a perfect vacuum or a calibrated pressure, depending on the application. On the other side is the pressure to be measured. The silicon chip changes its resistance with the changes in pressure. When the silicon chip flexes with the change in pressure, the electrical resistance of the chip changes. This change...

OBD Diagnostic Trouble Codes DTC

Diagnostic Trouble Codes or DTCs are generated by the on-board diagnostic system and stored in the ECM memory. They indicate the circuit in which a fault has been detected. DTC information remains stored in the ECM long term memory regardless of whether a continuous hard fault or intermittent fault caused the code to set. Toyota products with OBD will continue to store a DTC in the ECM long term memory until the code is cleared by removing power from the ECM BATT terminal. In most cases, the...

ESA Ignition System Operation

Rav4 Igniter Igt Transistor

In the example above, when the engine is cranked, an alternating current signal is generated by a 24-tooth Ne pickup and a four-tooth G pickup. These signals are sent to the ECU where they are conditioned and relayed to the microprocessor. The microprocessor drives a trigger circuit, referred to as IGt TR1 . The IGt signal is sent to the igniter to switch the primary circuit power transistor on and off. While cranking, IGt fixes spark timing at a predetermined value. When the engine is running,...

Air Temperature Sensor THA

Air Temperature Control System

The air temperature sensor monitors the temperature of air entering the intake manifold by means of a thermistor. This thermistor is integrated within the air flow meter on L type systems and located in the intake air hose just downstream of the air cleaner on D type systems. It has the same resistance characteristics as the water temperature sensor. 4 32 68 104 140 176 212 248 F Temperature ( F) 4 32 68 104 140 176 212 248 F Temperature ( F) This sensor has a two-terminal electrical connector...

Fuel Pump Test Terminals

Engine Control System

To facilitate testing and allow pump operation independent of the air flow meter or ECU control, all engines utilize a fuel pump test connector. There are two basic types of fuel pump test circuits. Most late model TCCS engines use an Fp test terminal located in the check connector. With the ignition switch on, jumpering +B to the Fp terminal sends current-directly to the fuel pump. Earlier engines use a jumper connector referred to as a 2P fuel pump check connector. This connector, when...

Distributorless Direct Ignition Systems Overview

Direct Ignition System Car

Essentially, a Distributorless Ignition System is an ignition system without a distributor. Eliminating the distributor improved reliability by reducing the number of mechanical Greater control over ignition spark generation - There is more time for the coil to build a sufficient magnetic field necessary to produce a spark that will ignite the air fuel mixture. This reduces the number of cylinder misfires. Electrical interference from the distributor is eliminated - Ignition coils can be placed...

Barometric Pressure Sensor

Barometric Pressure Sensor

The Barometric Pressure Sensor, sometimes called a High Altitude Compensator HAC , measures the atmospheric pressure. Atmospheric pressure varies with weather and altitude. At higher elevations the air is less dense, therefore, it has less pressure. In addition, weather changes air pressure. This sensor operates the same as the MAP sensor except that it measures atmospheric pressure. It is located inside the ECM. If it is defective, the entire ECM must be replaced.

Manifold Absolute Pressure Sensor D Type EFI

Manifold Pressure Signals

The D type EFI system eliminates the use of an air flow meter and uses a manifold absolute pressure sensor as a load measurement device instead. Because pressure in the intake manifold is proportional to the amount of air entering it, the manifold absolute pressure sensor is used to measure air intake volume in the D type EFI system. This sensor compares a variable pressure inside the intake manifold with a fixed reference pressure inside the sensor. A total vacuum chamber is placed on one side...

Where to Find Fuel Trim Data

The easiest way to perform a fuel trim inspection is to use your Diagnostic Tester. Fuel trim data is available on all OBD-II and most OBD data streams. The following chart indicates what fuel trim data is available for diagnosis Possible problem indicated outside of this range Accessed at VF1 terminal of check connector, TE1 off to injection system 5.0 volts lean condition 0 volts rich condition Target A F represents command to injection system 5.0 volts lean condition 0 volts rich condition...

Air Flow Sensor Terminal Identification First Design Sensor

Www Toyota Carina Airflow Sensor

Signal voltage representing air flow The air flow meter and ECU are wired as shown in the diagram. Signal characteristics are depicted by the accompanying graph. The use of battery voltage, VB, as a sensor input necessitates the use of the Vc terminal as a constant reference signal for the ECU. This is because battery voltage may change with variances in electrical load and ambient temperatures. Without the use of a constant reference voltage, these changes would cause a change in the Vs signal...