Learned Voltage Feedback and Target Air Fuel Ratio

Although Long FT, Target A F, and LVF (Learned Voltage Feedback) are essentially the same, there is a difference in how this data parameter is displayed on OBD engines. LVF and Target A F are displayed as a voltage signal with a range of 0 to 5 volts. The signal, which varies in fixed 1.25 volt increments, has a nominal value of 2.50 volts. When LVF is at 2.50 volts, it indicates that basic injection duration calculation is within 10 of required injection duration (to achieve 14.7 to 1 AFR). If...

IAC System Functional Tests

Because functional checks vary between the four major types of IAC systems, refer to the Repair Manual for specific procedures on performing an on-vehicle IAC inspection. On some late model OBD-II vehicles, an active test feature will allow you to manually command IACV positioning from fully open to fully closed. A quick check can be made by commanding a change to IACV positioning while watching for expected changes to idle rpm. The EGR System reduces NOx output by recirculating exhaust gases...

TWC Efficiency Quick Check CA Vehicles

On CA vehicles equipped with sub-O2 sensors, a quick check of TWC operation can be made by comparing the signal activity of the main oxygen sensor with the sub-oxygen sensor. Since the main O2S in located upstream of the converter and the sub-O2S is located downstream, a signal comparison would indicate whether a catalytic reaction is taking place inside the converter. If the catalyst is operating, the main O2S signal should normally toggle rich lean, while the sub-O2 sensor should react very...

Ammetersanalog And Digital

Ammeters measure amperage, or current flow, in a circuit, and provide information on current draw as well as circuit continuity. High current flow indicates a short circuit, unintentional ground or a defective component. Some type of defect has lowered the circuit resistance. Low current flow may indicate high resistance or a poor connection in the circuit or a discharged battery. No current indicates an open circuit or loss of power. Ammeters must always be connected in series with the...

Battery Types

PRIMARY CELL The chemical reaction totally destroys one of the metals after a period of time. Small batteries for flashlights and radios are primary cells. 2. SECONDARY CELLS The metals and acid mixture change as the battery supplies voltage. The metals become similar, the acid strength weakens. This is called discharging. By applying current to the battery in the opposite direction, the battery materials can be restored. This is called charging. Automotive lead-acid batteries are secondary...

Checks and Adjustments

The transmission requires regular maintenance intervals if it is to continue to operate without failure. As we discussed in previous sections, transmission fluid loses certain properties over time and especially due to heat. The Maintenance Schedules found in the repair manual or the Owners Manual indicate the appropriate replacement schedules based on how the vehicle is used. Schedule A for example, recommends replacement of the fluid every 20,000 miles or 24 months. Whereas Schedule B...

Clean Air Act Amendments of

On November 15, 1990, the Clean Air Act was amended, directing the Environmental Protection Agency (EPA) to promote new regulations, under section 207(a), requiring automobile manufacturers to install on-board diagnostic systems capable of. Identifying deterioration or malfunction of major emissions components which could result in vehicle failure to comply with federal emissions standards. Alerting the vehicle operator of the need to maintain and or repair emissions related components and or...

Computers And Logic Circuits

Dealing with computers can seem overwhelming for those who are accustomed to working with mechanical systems. Since we cannot actually see what is going on inside the computer or the system it controls, computers may not be as easy to understand as mechanical components such as transmissions and engines. However, computers are not as complicated as they might sound. This chapter will help demystify computers. The computers found on a vehicle are really no different than any other computer...

Construction

CASE Container which holds and protects all battery components and electrolyte, separates cells, and provides space at the bottom for sediment (active materials washed off plates). Translucent plastic cases allow checking electrolyte level without removing vent caps. 2. COVER Permanently sealed to the top of the case provides outlets for terminal posts, vent holes for venting of gases and for battery maintenance (checking electrolyte, adding water). 3. PLATES Positive and negative plates have a...

Diagnosis

During diagnosis, always verify the customer complaint. If the verification includes a test drive, be sure to check the level of ATF first. This will ensure that a low level is not contributing to the problem and give you an idea as to the condition and service that the vehicle has seen. Although preliminary checks suggest making adjustments, drive the vehicle before any adjustments in order to experience the same condition as the customer. If you are unable to verify the problem, ask the...

Diode Tests

Diodes can be checked with the alternator on the vehicle using a scope. Scope testing can identify open or shorted diodes, as well as problems in the stator coils. The scope patterns shown below include c) two diodes of the same polarity short-circuited f) one phase of the stator coil short-circuited g) one phase of the stator coil disconnected and, h) two phases of the stator coil short-circuited. This brief self-test will help you measure your understanding of The Charging System. The style...

Effects of IAC Operation on Emissions Driveability

Improper operation of the IAC system can have significant impact on idle quality and driveability. If idle speed is too low, the engine may stall or idle very rough. If idle speed is too high, harsh A T gear engagement may result. On some IAC systems, the IACV step count or ECM duty ratio may provide hints as to whether a major correction is being made to offset a idle speed problem. For instance, if false air entry causes idle speed to be much higher than normal, the IAC system may correct for...

Efitccs System

With the introduction of the Toyota Computer Control System (TCCS), the EFI system went from a simple fuel control system to a fully integrated engine and emissions management system. Although the fuel delivery system operates the same as Conventional EFI, the TCCS Electronic Control Unit (ECU) also controls ignition spark angle. Additionally, TCCS also regulates an Idle Speed Control device, an Exhaust Gas Recirculation (EGR) Vacuum Switching Valve and, depending on application, other engine...

EGR System Functional Tests

On some OBD-II vehicles, the EGR system can be controlled using the active test feature of the Diagnostic Tester. This is the easiest way to verify EGR system operation and can generally be performed as follows Start the engine and allow it to reach operating temperature Using the Diagnostic Tester, access the Active Test menu Select EGR System from the Active Test menu Raise engine speed and maintain a steady 3000 rpm Activate the EGR VSV (turn EGR On) You should notice a slight drop in engine...

Electronic Control Transmission ECT

The Electronic Control Transmission is an automatic transmission which uses modern electronic control technologies to control the transmission. The transmission itself, except for the valve body and speed sensor, is virtually the same as a full hydraulically controlled transmission, but it also consists of electronic parts, sensors, an electronic control unit and actuators. The electronic sensors monitor the speed of the vehicle, gear position selection and throttle opening, sending this...

Fuel Injection Volume Control

The amount of fuel injected depends on fuel system pressure and the length of time the injector is turned on. Fuel system pressure is controlled by the pressure regulator, and injector on time is controlled by the ECM. The time the injector is on is often called duration or pulse width, and it is measured in milliseconds (ms). Cold starting requires the highest pulsewidth. Pulsewidth is dependent primarily on engine load and engine coolant temperature. The higher the engine load and the more...

Functional Testing

Spark advance problems can result from an incorrect initial timing setting or a problem with spark advance during operation. Before attempting to check spark advance during operating conditions, the initial or base ignition timing setting should checked and adjusted. This procedure varies between systems, but on TCCS equipped vehicles, it generally requires jumping terminals at an underhood check connector (DLC1) to default the TCCS system to initial timing. After checking or adjusting initial...

IGF Detection Using Primary Current Method

The primary current level method measures the current level in the primary circuit. The minimum and maximum current levels are used to turn the IGF signal on and off. The levels will vary with different ignition systems. Regardless of method, the Repair Manual shows the scope pattern or provides you with the necessary voltage reading to confirm that the igniter is producing the IGF signal. Lack of an IGF on many ignition systems will produce a DTC. On some ignition systems, the ECM is able to...

Logic Circuits

As computers and solid state control modules become more prevalent on automobiles, some of the logic gate symbols that represent their internal circuits will show up more often. It is necessary to know not only what the logic symbols stand for, but to understand the basic operation of the circuits they represent when you analyze wiring diagrams during troubleshooting. Therefore, you should know a little about logic circuits and the symbols used to represent them. A logic gate symbol is simply a...

Operation

A detection circuit in the ECM detects the change and strength of current flow and puts out a voltage signal relatively proportional to exhaust oxygen content. NOTE This voltage signal can only be measured by using the Diagnostic Tester or OBD II compatible scan tool. The A F sensor current output cannot be accurately measured directly. If an OBD 11 scan tool is used, refer to the Repair Manual for conversion, for the output signal is different. The A F sensor is designed so that at...

Resistive Sensors Potentiometers

A potentiometer is a variable resistor that is commonly used as a sensor. A potentiometer has three terminals one for power input, one for a ground and one to provide a variable voltage output. A potentiometer is a mechanical device whose resistance can be varied by the position of the movable contact on a fixed resistor. The movable contact slides across the resistor to vary the resistance and as a result varies the voltage output of the potentiometer. The output becomes higher or lower...

Self Test

This brief self-test will help you measure your understanding of The Starting System. The style is the same as that used for A.S.E. certification tests. The answers to this self test are shown on next page. 1. The starting system has two circuits. They are the A. motor circuit and ignition circuit B. insulated circuit and power circuit C. motor circuit and control circuit D. ground circuit and control circuit 2. A basic starter control circuit energizes the magnetic switch through the ignition...

Selftest Answers

For the preceding self-test on The Battery, the following best complete the sentence or answer the question. In cases where you may disagree with the choice - or may simply want to reinforce your understanding -please review the appropriate workbook page or pages noted. 1 . B - The number and size of the plates determine current capability. (Page 2.) 2. A - When immersed in electrolyte, a cell produces about 2.1 volts (regardless of the number of size of plates). (Page 2.) 3. B - In a fully...

What is Serial Data

Serial data is electronically coded information which is transmitted by one computer and received and displayed by another computer. Using an analog digital circuit, the transmitting computer digitizes the data from sensors, actuators, and other calculated information. Typically, this means that each sensor or actuator value is converted into a one byte (8 bits) binary word before it is transmitted to the receiving computer. In order to display the data in familiar units that you are used to...

OBDII OnBoard Diagnostic System Generation

Although OBD supplies valuable information about a number of critical emissions related systems and components, there are several important items which were not incorporated into the OBD standard due to technical limitations at the time that the system was phased into production (during the 1988 model year.) Since the introduction of OBD, several technical breakthroughs have occurred. For example, the technology to monitor engine misfire and catalyst efficiency has been developed and...

OBDII OnBoard Diagnostic System Generation Continued

As a result of these technical breakthroughs and because existing I M programs have proven to be less effective than desired in detecting critical emissions control system defects which occur during normal road load operation, a more comprehensive OBD system was developed under the direction of CARB. OBD-II, which is implemented over the 1994 through 1996 model years, adds catalyst efficiency monitoring, engine misfire detection, canister purge system monitoring, secondary air system...

Incorrect Injection Duration

In addition to the problems mentioned above, false sensor input from any of the six major input sensors can also cause the air fuel ratio to shift sufficiently to cause driveability and or emissions concerns. If engine load is incorrectly calculated, fuel requirements are also miscalculated, resulting in a driveability or emissions concern. This type of a condition can be identified by reading sensor signals and comparing them to standard values. With this type of condition, the ECM adaptive...

Closed Loop Control System Functional Checks

If you suspect that the closed loop system is not properly controlling fuel delivery, one of the first checks you should perform is an Oxygen (02) Sensor signal check. Since the ECM relies on the 02S signal to fine tune injection duration during closed loop operation, an accurate check of the 02S signal is crucial in diagnosing problems that you suspect are the result of improper closed loop control. Remember, the engine (and engine control system) must meet certain conditions prior to checking...

Types of VAF Meters

There were two major types of VAF meters. The first design, is the oldest type. It uses battery voltage for supply voltage. With this type of VAF meter, as the measuring plate opens signal voltage increases. Two were two different VAF designs. The newest type, second design, the voltage decreases as the measuring plate opens.

Standardization of Service Information and DTCs

Under the provisions of OBD-II regulations, emissions related diagnostic and service information will be readily available to the service industry, from the vehicle manufacturer. This information includes procedures and specifications necessary to diagnose the engine control system. Although enhanced diagnostics may be available using special equipment and procedures, at a minimum, repair procedures will be written using the generic scan tool and other commonly available test equipment like...

Power Side Switch Circuit

A power side switch is a switch located between the power supply and load. Sometimes the power side switch is called hot side switch because it is located on the hot side, that is, before the load, in a circuit. The Stop Lamp switch is a good example. When the brake pedal is depressed, the Stop Lamp switch closes sending battery voltage to the ECM. This signals the ECM that the vehicle is braking. The following switches act as switches for the ECM. Usually, they are supply side switches. Note...

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...

Fuel System Monitoring

Most fuel systems continually shift their base calibration to compensate for changes in atmospheric pressure, temperature, fuel composition, component variations, and other factors. This adaptive behavior is normal as long as it remains within the design limits of the system. When conditions occur which cause the fuel system to operate outside of its design parameters, for example, a skewed air flow meter signal, incorrect fuel pressure, or other mechanical problems, the OBD-II system is...

PCV System Operation

Toyota Pcv Valve

Like the previous system, this system also uses manifold vacuum to draw crankcase vapors back into the intake manifold. Typically, blowby production is the greatest during high load operations and very light during idle and light load operations. Since the characteristics of manifold vacuum do not match the flow requirements needed for proper crankcase ventilation, a PCV valve is used to regulate blowby flow back into the intake manifold. During idle and deceleration, blowby production is very...

Readiness Test Continued

The readiness test is a flag which is used during I M inspections to indicate that the vehicle on board diagnostic system cannot supply information required during the test. In this case, the vehicle must be operated until all readiness testing conditions have been satisfied. When entering CARS OBD-il diagnostic functions, this display will appear if the ECM has not completed all of its continuous monitor or once per trip dynamic tests. NOT ALL SUPPORTED ON-BOARD SYSTEM READINESS TESTS HAUE...

Visual Inspection

Battery service should begin with a thorough visual inspection. This may reveal simple, easily corrected problems, or problems that might require battery replacement. 1 . Check for cracks in the battery case and for broken terminals. Either may allow electrolyte leakage. The battery must be replaced. 2. Check for cracked or broken cables or connections. Replace, as needed. 3. Check for corrosion on terminals and dirt or acid on the case top. Clean the terminals and case top with a mixture of...

Electrical Load Sensor ELS

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...

Injector Maintenance and Cleaning

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...

Malfunction Indicator Light MIL

When a malfunction occurs, the MIL remains illuminated as long as the fault is detected and goes off once normal conditions return, leaving a Diagnostic Trouble Code (DTC) stored in the ECM memory. Circuits are monitored for continuity, shorts, and in some cases, normal parameter range. The Malfunction Indicator Light (MIL) is also a visual inspection item in most emissions inspection and maintenance programs U M), allowing the emissions inspector to make a quick visual determination whether...

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...

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.

Ignition Timing

All engines equipped with TCCS utilize a test terminal (T or TE1) somewhere under the hood. Early TCCS utilizes a two-terminal check connector in the wiring harness. This yellow body connector contains circuits T and E1, which when jumpered, default the TCCS system to initial timing. The location of this test terminal varies between applications. Refer to the appropriate repair manual for connector location. A new design multipurpose check connector began phase-in starting with 1985 models. By...

NE Signal and G 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...

Charging

A battery in good condition may occasionally fail to crank the engine fast enough to make it start. In such cases, the battery may require charging. All battery chargers operate on the same principle an electric current is applied to the battery to reverse the chemical action in the cells. Never connect or disconnect leads with the charger turned ON. Follow the battery charger manufacturer's instructions. And, do not attempt to charge a battery with frozen electrolyte. When using a battery...

Step Battery Voltage Correction

The final step is a battery voltage correction. The input signal used in battery voltage corrections is 0 Battery Voltage (+B) There is an operational delay between the time the ECU sends the injection signal to the driver circuit and the actual opening of the injector. This delay changes with the strength of the magnetic field around the injector coil. The delay increases as battery voltage falls. To determine final injection duration, the ECU corrects for injector opening delay by using a...

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...

Ignition Advance Service

Though the Diagnostic Tester shows the computed ignition, advance, using a timing light confirms that advance took place and the timing marks are in the correct position. With Distributor Ignition Systems, the point at which ignition occurs may vary because the base reference point can be moved. It is critical that the base reference point be set to factory specifications. With DLI and DIS, the base reference point is determined by the Crankshaft Position Sensor and rotor, which is...

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...

Engine Cranking Signal STA

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...

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...

Electrical Diagnostic Testing Onboard Diagnostics

The ECU is equipped with a built-in self diagnostic system, which monitors the speed sensors, solenoid valves and their electrical circuitry. If the ECU senses a malfunction 1. It blinks the OD OFF light to warn the driver. 2. It stores the malfunction code in its memory. 3. (When properly accessed) it will output a diagnostic code indicating the faulty component or circuit. Once a malfunction is stored in the memory system, it will be retained until canceled (erased). The vehicle battery...

Vane Air Flow Meter L Type EFI

The vane type air flow meter is a commonly used air volume measurement device on Toyota EFI engines. The meter consists of a measuring plate, which is spring loaded closed by a return spring, and a potentiometer attached to the plate, which varies an electrical signal to the ECU as the position of the plate changes. Air volume entering the engine is directly proportional to the amount of movement detected from the measuring plate. Additionally, the air flow meter incorporates a fuel pump enable...

Fuel Pressure and Volume Testing

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...

No Spark Output

Igniter Coil Rav4 Diagram

The following procedures assume that a 3) spark tester reveals no spark at two different cylinders while the engine is cranked. These procedures and specifications are general guidelines. Consult the appropriate repair manual for more specific information about the vehicle you are troubleshooting. 1) Ensure battery condition prior to ignition system analysis. 2) Check and confirm good connections at distributor, igniter, and coil. 3) Basic secondary leakage checks at coil and coil wire. 1)...

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...

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...

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...

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...

What Is Igf Signal

Igf Signal

On Conventional EFI engines, the IG signal is used to inform the ECU of engine rpm. This signal is generated directly from the coil negative terminal or from an electrically equivalent point inside the igniter on the early P-7 2S-E engine. Conventional EFI engines do not use an Ne or G sensor and do not use an IGf signal. The IG signal is also used by the ECU to trigger injection pulses therefore, if this signal is lost, the engine will stall for lack of injection pulse.

Starting Injection Control

To provide accurate fuel injection duration during cranking periods, the ECU uses a program which determines a basic injection volume based on engine coolant temperature. Once a basic injection duration is calculated, corrections are made for intake air temperature and battery voltage (which is typically low under cranking load). Basic injection duration while cranking is increased at low coolant temperatures. Injection duration while cranking is corrected for battery voltage by increasing...

Effects of Oxygen Sensor Degradation

Since the oxygen sensor is the heart of the closed loop control system, proper operation is critical to efficient emission control. There are several factors which can cause the oxygen sensor signal to degrade and they include the following Silicon contamination from chemical additives, some RTV sealers, and contaminated fuel. Lead contamination can be found in certain additives and leaded motor fuels. Carbon contamination is caused by excessive short trip driving and or malfunctions resulting...

Ignition Advance Modes and Corrections

The ECM calculates the IGT signal on time based on engine operating modes and conditions. The IGT signal is based primarily on the crankshaft position sensor signal, engine load, temperature, knock Initial Ignition Timing Angle Basic Ignition Advance Angle Warm-Up Correction Over-Temperature Correction Stable Idling Correction EGR Correction Air-Fuel Ration Feedback Correction Knocking Correction Torque Control Correction Other Correction Maximum And Minimum Advance Angle Control

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...

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...

Sub Oxygen Sensor OX

The sub-oxygen sensor is used on California and some Federal engines. It is used to monitor the exhaust stream after the catalyst to determine if the air fuel mixture is within the range for efficient converter operation. The sub-oxygen sensor is identical to the Zr02 main oxygen sensor located ahead of the catalyst. Information from this sensor is used by the ECU to fine tune the air fuel ratio and improve emissions. Oxygen Sensor Terminal Identification Oxygen Sensor Terminal Identification...

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,...

Fixed Orifice PCV System

On some early Toyota EFI vehicles, a fixed orifice PCV system is used to meter blowby from the crankcase into the intake manifold, where they would be consumed during normal engine operation. This system is simple in design and construction, and provides crankcase ventilation based on the size of the fixed orifice valves and the normal operating characteristics of intake manifold vacuum. The two fixed orifice valves are used to balance the strength of vacuum applied to the crankcase as engine...

Main Relay Circuits

Toyota Camry Efi Main Relay

Toyota utilizes several different EFI Main Relay circuits depending on application. These circuits can be categorized into four distinct types. 1 Dual contact EFI Main Relay, ignition switch controlled 2 Single contact EFI Main Relay, ignition switch controlled 3 Dual EFI Main Relays, ignition switch or ECU controlled 4 Single contact EFI Main Relay, ECU controlled Generally speaking, the EFI Main Relay supplies current to the following major circuits Injectors dual relay or dual contact relay...

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...

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...

EGR Vacuum Modulator

Egr Exhaust Back Pressure

Because exhaust backpressure increases proportionally with engine load, the EGR vacuum modulator uses this principle to precisely control the strength of the vacuum signal to the EGR valve. The typical EGR control system uses two ported vacuum signals from the throttle body. Port E is the first stage ported vacuum signal and Port R is the second stage ported vacuum signal uncovered by the opening throttle valve. When vacuum is applied from port E, the strength of the vacuum signal applied to...

Battery Voltage Correction

The applied voltage to the fuel injector will affect when the injector opens and the rate of opening. The ECM monitors vehicle system voltage and will change the injection on time signal to compensate. If system voltage is low, the injection on time signal will be longer, but the actual time the injector is open will remain the same if system voltage were higher . When the evaporative purge valve is on, fumes from the charcoal canister are drawn into the intake manifold. The ECM will compensate...

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...

Positive Crankcase Ventilation System

Pcv System Diagram

During normal compression stroke, a small amount of gases in the combustion chamber escapes past the piston. Approximately 70 of these blowby gases are unburned fuel HC that can dilute and contaminate the engine oil, cause corrosion to critical parts, and contribute to sludge build up. At higher engine speeds, blowby gases increase crankcase pressure that can cause oil leakage from sealed engine surfaces. The purpose of the Positive Crankcase Ventilation PCV system is to remove these harmful...

Toyota Camry Electrical Wiring Diagram

Color Abbreviations

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...

Misfire Monitoring

Misfire Monitoring

By using a high frequency crankshaft position signal, the ECM can closely monitor crankshaft speed variations during individual cylinder power strokes. When an engine is firing cleanly on all cylinders, the crankshaft speeds up with each power stroke. When misfire occurs, crankshaft speed increase is effected for that cylinder. Toyota OBD-II engines use a 36 minus 2 tooth Ne sensor which directly measures crankshaft speed and position. This information is processed by the ECM to determine if...

Manifold Absolute Pressure MAP Sensor

Inside Manifold Absolute Map Sensor

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...

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...

Decel Dashpot and Throttle Opener Systems

Vsv Valve 3sfe

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...

Uses and Limitations of Scan Tool Serial Data for Diagnosis

Scan Tool Serial Data

A scan tool is an exceptionally useful tool when diagnosing engine control system problems. It gives you access to vast quantities of information from a conveniently located diagnostic connector. A scan tool allows a quick check of sensors, actuators, and ECM calculated data. For example, when checking for sensor signals which may be shifted out of normal range, scan data allows you to quickly compare selected data to repair manual specifications or known good vehicle data. When checking for...

How Long FT Works

Long FT is a data parameter on the OBD and OBD-II data streams. It is a more permanent correction to fuel delivery because it is part of the basic injection duration calculation. Long FT changes slowly, in response to Short FT. Its normal range is 20 , positive values indicating rich correction and negative values indicating lean correction. If Short FT deviates significantly from 10 for too long, the Long FT shifts, changing the basic injection duration. This shift in basic injection duration...

Shift Lock Mechanism

Rav4 Lock Mechanism

The shift lock mechanism is made up of a number of components as seen in the illustration below. The shift position switch shift lock control switch is used to detect the position of the shift lever. It has two contacts, P1 and P2. When the select lever is in the Park position, P1 is on closed and P2 is off open . In this position, the key can be removed but the select lever is locked in position. When the select lever is in a position other than Park, P1 is off open and P2 is on closed . In...

G or G Signal Group

Signal Toyota

The G signal generator is very similar to the Ne signal generator. The G1 signal represents the standard crankshaft angle and is used by the ECU to determine ignition and injection timing in relation to TDC. Depending on engine, there are different variations of Ne and G1 signal generators. The following illustrations show the relationship between the Ne and G1 signals and the different variations of signal generators.

Current Draw Test

Voltmeter Battery Current Drain Test

A starter current draw test provides a quick check of the entire starting system. With the Sun VAT-40 tester, it also checks battery's cranking voltage. If another type of tester is used, follow the manufacturer's recommended procedure. The starting current draw and cranking voltage should meet the specifications listed for the Toyota model being tested. Typical current draw specs are 130-150 amps for 4-cylinder models and 175 amps for 6-cylinder models. Cranking voltage specs range from 9.6 to...

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...

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...

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...

Serial Data Streams

Obd Serial Data

Although not required by the OBD regulation, the use of serial data accessible by special scan tools, has been introduced by some manufacturers. Serial data is electronic information about sensors, actuators, and ECM fuel spark strategy, which is accessed from a single wire coming from the ECM. The term serial data implies that the information is digitally coded and transmitted in a series of data words. The data words are decoded and displayed by a scan tool. The typical Toyota OBD serial data...

Procedures to Retrieve Trouble Codes

Toyota Corolla Ae100 Diagnostics

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...

Malfunction Indicator Light Illumination

Once a malfunction has been established two trip detection logic where applicable the MIL will illuminate and remain illuminated even if the condition is intermittent. The MIL will remain on after subsequent restarts even if the malfunction condition is no longer present. The OBD-II system can only extinguish the MIL if the malfunction does not reoccur during three subsequent sequential trip cycles. The OBD-II system can only erase a stored DTC if the malfunction is not detected during forty...

Stateofcharge Test

The state-of-charge test checks the battery's chemical condition. One method uses a hydrometer to measure the specific gravity of the electrolyte. Another method uses a digital voltmeter to check the battery's open circuit voltage and, for a general indication of the battery's condition, check the indicator eye if the battery has one or check the headlamp brightness during starting. Specific gravity means exact weight. The hydrometer compares the exact weight of electrolyte with that of water....

Step Motor IAC System

2001 Highlander Air Bypass Passageway

This system uses a step-motor type IACV to control bypass airflow. The IACV consists of a stepmotor with four coils, magnetic rotor, valve and seat, and can vary bypass airflow by positioning it's valve into one of 125 possible steps. Basically, the higher the IACV step number, the larger the airflow opening and the greater the volume of air bypassed around the closed throttle. The ECM controls IACV positioning by sequentially energizing its four motor coils. For each coil that is pulsed, the...

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...

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.

Throttle Position Sensor

Tps Signal Voltage

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...

Assignmentname

Describe the basic construction of a lead-acid battery. 2. Explain what materials are used to make up the positive plate, negative plate, and electrolyte. 3. Describe the basic chemical operation of a single cell that makes a battery. 4. List the voltage output of both a single battery cell and a six cell automotive battery. Be exact. 5. Explain the four basic battery capacity ratings systems. 6. List the gases that are produced during the charging process from both the positive and the...

Oxides of Nitrogen NOx Emission

Nox Engine

High cylinder temperature and pressure which occur during the combustion process can cause nitrogen to react with oxygen to form Oxides of Nitrogen NOx . Although there are various forms of nitrogen-based emissions that comprise Oxides of Nitrogen NOx , nitric oxide NO makes up the majority, about 98 of all NOx emissions produced by the engine. Generally speaking, the largest amount of NOx is produced during moderate to heavy load conditions when combustion pressures and temperatures are their...

ECT Analyzer

Ect Analyser Toyota Transmission

The ECT Analyzer is designed to determine if a transmission malfunction is ECU electrical circuit related or in the transmission. The analyzer is connected at the solenoid electrical connector using appropriate adapter harnesses. The vehicle is driven using the analyzer to shift the transmission. If the transmission operates properly with the ECT Analyzer, the fault lies between the solenoid connectors up to and including the ECU. On the other hand, if the transmission does not operate properly...

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...