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System of onboard diagnostics (OBD) - a principle of functioning and codes of malfunctions
Data on diagnostic devices
 | Check of serviceability of functioning of components of systems of injection and emission control is performed with a universal digital meter (DMM). Using a digital meter is preferred for several reasons. First, on analogue devices it is rather difficult (sometimes impossible) to determine the result of readings with an accuracy of hundredths and thousandths of, while at inspection of the contours including in the structure electronic components, such accuracy takes on special significance. The second, no less important reason is the fact that the internal contour of a digital multimeter, has high enough impedance (internal resistance of the device is 10 million ohms). As the voltmeter is connected to a checked chain in parallel, accuracy of measurement is higher, the smaller parasitic current will flow through the device itself. This factor is not significant when measuring relatively high voltages (9 ÷ 12), but becomes the determining the diagnosis of issuing low voltage components, such as, for example, oxygen sensor, which refers to the measurement of a volt. |
 | The most useful tools for the diagnosis of engine management systems of modern car models are handheld readers scanner type. Scanners are the first generation to read fault codes systems OBD-I. Before use, the reader should be checked for compliance with the model and year of manufacture of the car inspected. Some scanners are multi-functional, due to the possibility of changing the cartridge depending on model of the diagnosed car (Ford, GM, Chrysler, etc.), while others are linked to the requirements of regional authorities and are intended for use in certain areas of the world (Europe, Asia, the United States and etc.). |
With the introduction of the production meets the requirements of recent legislation on environmental protection systems of onboard diagnostics of the second generation (OBD-II) was started readers a special design. Some manufacturers have adjusted release of the scanners for use by mechanics-fans at home - ask in shops of automobile accessories.
 | Also produced a different type of scanner for reading from the memory of the onboard processor by directly connecting to the diagnostic connector of the main spit vehicle wiring. |
General description of the OBD system
All are described in this manual models are equipped with on-board diagnostics (OBD). On models 1993 and 1994 Vol. apply system OBD-I, since 1995 all cars were staffed by second-generation diagnostic systems (OBD-II).
The main elements of both systems is the onboard processor, more often called the electronic module of management of functioning of the power unit (PCM). PCM is the brain of the engine management system. Input data is input to the information from various sensors and other electronic components (circuit breakers, relays, etc.). Based on the analysis of information received from the sensor data and in accordance with laid down in the basic parameters of the processor memory, RSM develops commands on operation of various control relays and actuators, thereby effecting adjustment of the operating parameters of the engine and providing peak efficiency of its return at the minimum fuel consumption.
On the service components of engine management systems / emission control are subject to special warranty with extended validity period. Do not attempt to self-diagnose failures PCM or replace system components before the release dates of these obligations, - address to experts branded service stations of Toyota.
Information gauges
Camshaft position sensor (CMP) - The sensor generates data signals, based on an analysis which determines the current phase of PCM timing and engine speed, using the information in the management of sequential injection and ignition of air-fuel mixture in the combustion chambers.
The sensor (s) of the crankshaft position (CKP) - All models from 1995 MY. two sensors TFR, whereas earlier models used only one such sensor. Incoming signals from sensors used PCM as a reference when determining the engine speed and TDC position of the piston of each cylinder. On the basis of information received PCM controls the sequence of the injection and ignition of air-fuel mixture in the combustion chambers. In systems OBD-II Raman signals generated by sensors are also used in the diagnosis of failure of the power unit.
Sensor Engine Coolant Temperature (ECT) - On the basis of information received from the sensor PCM makes the necessary adjustments of the air-fuel mixture and ignition timing, and controls the operation of the system EGR.
Temperature sensor EGR - from the sensor information is used in determining the intensity of the exhaust gas recirculation in the receive path of the engine.
The fuel temperature sensor - RSM uses the information emitted by the sensor in the diagnosis of failure of system components.
Intake air temperature (IAT) - RSM uses coming from the IAT sensor information when adjusting the parameters of injection, ignition timing systems and in the management of the operation of EGR.
Knock sensor - The sensor is a piezoelectric element, which responds to changes in the intensity of the vibration of the engine. Based on the analysis of information coming from the PCM encoder performs correction ignition angle for timely elimination occurring in combustion chambers detonation air-fuel mixture with potentially premature wear of the internal components of the engine.
The gauge of absolute pressure in the pipeline (IDA) (model 1996 Vol.) - Sensor monitors variations in the depth of the vacuum in the intake manifold, associated with changes in crankshaft speed and engine load, and converts the received information in the signal amplitude. Information from the sensors is used by the management in the diagnosis of engine failures.
Meter air mass (MAF) - MAF sensor determines the volume-weighted parameters entering into the inlet duct air stream. As a sensitive element in the sensor uses a filament. PCM uses a supplied MAP sensor and IAT the information at thin adjustments of injection parameters.
Oxygen sensor (l-probe) - The sensor produces a signal whose amplitude depends on the ratio of oxygen (O 2) contained in the exhaust gases of the engine and the outside air. On the basis of information received from the sensor determines the parameters of the PCM air-fuel mixture, promptly carrying out its enrichment or depletion.
The gauge-switch fluid pressure system hydrostrengthening wheel (PSP) - On the basis of input from the gauge-switch PSP information PCM enhances the idle speed (due to the operation of the valve IAC) to compensate for the increasing loads on the engine, linked to the operation of the steering hydraulic booster at fulfillment maneuvers.
Throttle Position Sensor (TPS) - The sensor is located on the throttle body and is connected to the throttle shaft. The amplitude signal outputted TPS RSM determines the angle of the throttle opening (controlled by the driver from the accelerator pedal) and adjusts the fuel supply into the intake ports of the combustion chambers. Sensor failure or weakening of its fastening leads to faults of injection and infringements of stability of turns of idling.
The vehicle speed sensor (VSS) - As its name implies, a sensor informs the processor of the current vehicle speed.
Other controlled by RSM characteristics - In addition to the sensors listed above issued to PCM comes as further details about the functioning of various components and systems that determine the performance of the engine. Among others, systems and components, control the operation of which carries PCM include:
a) The air conditioning system;
b) ABS;
c) battery (output voltage);
d) System EVAP;
e) the ignition switch;
f) The gauge-switch of the permission of start;
g) ground circuit;
h) the operation of the transmission control system.
Actuators
Relays functioning clutch R / C - PCM carries off the compressor K / V during an intense acceleration.
The control lamp "Check up the engine" - PCM makes inclusion of the warning lamp in the event of failures of functioning of the engine management system.
Relays operation of the cooling fans - PCM controls the operation of the cooling fan on the basis of the analysis of the signals from the coolant temperature sensor.
Vacuum control solenoid valve EGR - On models up to 1999 MY. PCM controls the degree of opening of the vacuum to the EGR valve through a special intermediate solenoid valve.
Valve EGR - On models 1999 Vol. PCM controls the flow of exhaust gas recirculation valve via an electronic EGR.
The valve purge of a coal adsorber - This solenoid valve actuating team RSM performs a purge of a coal adsorber EVAP, bringing accumulated inside the fuel vapor into the intake tract of the engine.
Solenoid valve of turns of fast idling - This valve is used on models from 1995 MY. and serves to increase the idle speed during cold weather. In fact, the valve acts as the choke on carburettor models.
Front Mount power unit - On some models, the PCM also controls the stiffness of the front engine mount, depending on vehicle speed. Minimization of vibration is done by selecting one of the two support units.
Injector fuel injection - PCM provides individual inclusion of each of injectors according to the established order of ignition. In addition, the module controls the duration of opening of injectors, determines the width of the control pulse, measured in milliseconds, and the amount of fuel injected into the cylinder. For more information on the basis of the system of injection, replacement and service of injectors, see Chapter power supply system and release.
Fuel pump relay - Relay control module is activated by turning the ignition switch to START / RUN. When the ignition switch is supplying power to the fuel pump, which provides a pressure rise in the path of the power supply system of the car. For more information on the location and operation of the relay, refer to Chapter Onboard electric equipment and power supply system and release.
The valve of stabilization of turns of idling (IAC) - IAC valve carries the dosage amount of air bypassed bypassing the throttle valve when the latter is closed, or occupies the idle position. Valve opening and the formation of the resulting air flow controls the PCM.
Oxygen sensor heater - The functioning of the device carries PCM. Heater produces a rapid warm-up l-probe to normal operating temperature.
Power transistor - transistor provides signal amplification ignition produced by PCM and at the right time produces an instant chassis ground of the primary circuit of the ignition system, causing the secondary side of the generation of explosive signal output coil (s) directly to the spark plug (see chap. Electric motor).
Solenoid valve control the operation of power - on models 1993 and 1994 Vol. control the operation of valve power carries PCM through a special magnet.
Module operation control knob (SCI) - SCI, being separate from the PCM control module receives information signals from various sensors, such as VSS, the sensor switch permits startup of the turbine shaft speed sensor, TPS, CMP, etc., and uses received data to determine when shift transmission AT, a desired pressure in the path and angular locking of the rotation.
Read fault codes
If any malfunction repeating successively in spirit trips, the PCM commands the switch mounted in the instrument panel of a control lamp "Check up the engine", also referred to as an indicator of failure. The lamp will continue to burn until the violation will not disappear and will not appear for three or more trips.
 | Read fault codes in the OBD-II may be carried out in two ways. In the first case it is necessary to provide access to the RSM for the purpose of the selector switch on the flashing codes via the diagnostic lamp / control lamp "Check up the engine". PCM should be removed from its support bracket (without disconnecting the wiring) and act in accordance with the instructions below.
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Models 1993 and 1994 Vol.
a) Turn the ignition switch (without starting the engine). The control lamp "Check up the engine" on the instrument panel must remain switched on, which confirms the granting it the power of the PCM and the condition of the lamp.
 | Violation of the procedure described below procedure can lead to occasional cleaning of the PCM memory! |
b) Using a screwdriver turn the selector on the side of the PCM to fully clockwise. Should start flashing diagnostic lamp - after three flashes, turn selector fully counter-clockwise;
c) Closely monitor the operation of the diagnostic lamp. The red LED is used to highlight the first digit of the DTC, the second digit of the green LED flashes. For example, the code (chain TPS) 43 is as follows: four glimmer of red diode, then three flashes green. The absence of the identified violations of the system shows the flashing code 55 (see. Below in this section map the fault codes);
d) If the ignition is turned on again after turning it in code reading system automatically cancels the preceding results of the search and the process needs to start reading again. Note: Starting the engine automatically shuts off the system self-test.
Models from 1995 MY.
a) Turn the ignition switch (without starting the engine). The control lamp "Check up the engine" on the instrument panel must remain switched on, which confirms the granting it the power of the PCM and the condition of the lamp.
| Violation of the procedure described below procedure can lead to occasional cleaning of the PCM memory! |
b) Using a screwdriver turn the selector on the side of the PCM to fully clockwise. Should start flashing diagnostic lamp - after three flashes, turn selector fully counter-clockwise;
c) Closely monitor the functioning of a control lamp "Check up the engine". The lamp will display the first digit of a series of long (about 0.6 s) flashes, and then, after a 2-second pause, will start flashing the second digit in the form of a series of short (by 0.3 s) flashes. In order to determine the displayed code, write down the number of flashes of each series, so the code 0403 (chain TPS) will be as follows: 4 long glimpse, then, after a pause, three short. The absence of the identified violations of the system shows the flashing code 0505 (see. Below in this section map the fault codes);
d) If ignition is turned on again after switching off for him in the process of reading the code, the system automatically cancels the preceding results of the search and the process needs to start reading again. Note: Starting the engine automatically shuts off the system self-test.
 | The second method involves the use of a special scanner, and applies only to models equipped with OBD-II (since 1995 vol.). using a scanner can be made more profound diagnosis of the state of the engine and a fine estimation of its operating parameters. In addition, the scanner allows to produce frozen OBD system reads the data at the time of occurrence of unstable failure.  | When using the scanner uses a different form of the code used other than when reading through a control lamp "Check up the engine". In this case prefix the type P0 or P1 (see. Section of the table corresponding to the code card). In the absence of a hand scanner diagnosis of unstable disturbances engine management system can only be made in the workshop car service. |
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Clear Memory ECM / PCM
Once identified in the diagnostic process violations are eliminated, it should be clear from the PCM memory recorded in her fault codes.
| Do not clean the memory by disconnecting the negative cable from the battery - it will also lead to the loss of the basic parameters and infringement of stability of turns of idling for the first time after starting the engine. |
| When using the scanner OBD-II systems should put the unit into "CLEARING CODES" and act in accordance with the manufacturer's instructions.
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Models 1993 and 1994 Vol.
a) That the recorded memory of fault codes;
b) Wait at least two seconds, then turn the selector on the side of the PCM to fully clockwise, - LEDs should start blinking;
c) After the four flashes diodes turn selector fully counter-clockwise;
d) Turn the ignition off.
Models from 1995 MY.
a) That the recorded memory of fault codes;
b) Wait at least two seconds, then turn the selector on the side of the PCM to fully clockwise;
c) Wait for at least two seconds and turn selector fully counter-clockwise;
d) Turn the ignition off.
Memory cleaning must be carried out always before the first engine start after replacing the engine control system components. If the memory module has been recorded fault code of any of the information sensors, if after replacement of the failed component to produce engine start without purification of memory, the old code remains valid and the system switches to the basic facilities, excluding the new sensor from among the workers components.
| During the first 15 ÷ 20 seconds after the first run of the engine speed may be unstable due to the reduction of processor performance. |
Identification codes of malfunctions of the engine uparvleniya
The specifications are complete map of possible fault codes, not all of which can occur for a particular vehicle equipment.
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