LEXUS RX 300

1998 - 2003 of launch

Repair and operation of the car

Application of an oscillograph of observation of signs in chains of systems of control

The digital multímetros perfectly healthy convenient for the check of the electric chains that are in a static state, and also to fix of slow modifications of the drawn parameters. Carrying out the dynamic controls that are executed in the work motor and also in the moment of the identification of the reasons of periodic failures the oscillograph becomes the instrument absolutely irreplaceable.

Some oscillographs allow to guard oscillograms in the built module of the memory with the subsequent results conclusion to the press or his copy to the digital haulage company already in stationary conditions.

The oscillograph allows to observe periodic signs and to measure characteristics of rectangular impulses, and also levels of the tension that is modified slowly. The oscillograph can be in use for:

• Identifications of failures of unstable character;
• Checks of results of the done corrections;
• Activity that controls probe of lambda;
• The analysis of the signs developed a probe of lambda what I divert of parameters of the standard is an unconditional evidence of the violation of the usefulness of the functioning of a system of control in general - from another side, the fairness of the form of the given impulses a probe of lambda can serve of a guarantee fiável of the lack of violations in a control system.

The confidence and the simplicity of the operation of oscillographs modern do not demand of the operator of special special knowledge and experience. The interpretation of the obtained information can be done easily by the elementary visual comparison of the oscillograms withdrawn during conferem with the typical temporary dependences for several sensors and the mechanisms of actuation of the motor systems of control given down.

Parameters of periodic signs

Each sign withdrawn through an oscillograph can be described through the next key parameters:

• vastness – a difference of the very and least tension (of V) of a sign inside the period;
• the period – duration of a cycle of a sign (milissegundo);
• frequency – the number of cycles for as (Hz);
• width – duration of a rectangular impulse (milissegundo, I microsecond);
• the porosity – the relation of period of repetition to the width (In the foreign terminology the return is the porosity applied the parameter called by a current cycle, definite in the %);
• the form of sign – the sequence of rectangular impulses, the only emissions, a sinusoid, impulses tooth of mountain range, etc.

Normally the characteristics of the defective device strongly are differentiated of the reference that allows to an operator to reveal easily and quickly visually the refused component thing.

The signs of a continuous current - only transmit what the tension analyses.

The signs of the alternate current - are the analysed vastness, the frequency and the form of a sign.

Explosions sensor

The signs modulated by the frequency - are the analysed vastness, the frequency, the form of a sign and the width of periodic impulses.

Sensor inductive CKP

Sensor inductive CMP

Sensor inductive VSS

Meters of REVOLUTIONS PER MINUTE and provisions of end that works in the Hall effect

Meters of REVOLUTIONS PER MINUTE opticians and provisions of end

Digital MAF and sensors of MAP

The signs modulated in the width of an impulse (ShIM) - are the analysed vastness, the frequency, the form of a sign and the porosity of periodic impulses.

Fuel injector

Device of stabilization of turns of X/X (IAC)

Primary curve of the roll of ignition

Them Ø/m EVAP system adsorber purges the valve

Valves of system of EVAP

The form of the sign given by an oscillograph depends on the group of several factors and can be modified considerably.

In a look said before the initial substitution of the component one suspected in case of the discrepancy of the form of the diagnostic sign withdrawn with the reference oscillogram, it is necessary to analyse the carefully received result.

Tension

The null level of a sign of reference cannot be considered as an absolute basic value, - the true "null" sign depending on concrete parameters of the checked chain can move somewhat reference (1 sees the variety in an illustration the digital Sign) inside certain admissible variety (2 to see the variety in an illustration the digital Sign and 1 in an illustration the Analogous sign).

The vastness full of a sign depends on the voltage of provision of the checked outline and also it can vary somewhat the value of reference in certain limits (2 sees the variety in an illustration the digital Sign and 2 in an illustration the Analogous sign).

In chains of a vastness of continuous current of a sign it limits itself to supply to the voltage. It is possible to give a chain of the system of the stabilization of turns of wasting time (IAC) what they alarm the tension is not modified with the modification of turns of the motor of any way like an example.

In chains of the vastness of sign of current alternated already inequivocamente it depends on the frequency of the work of a fountain of a sign, so, the vastness of the sign given by the sensor of the provision of an end of inclination (CKP) will increase with the increase in turns of the motor.

In a stated look if the vastness of the sign withdrawn through an oscillograph is excessively low or high (up to the decoration of high levels), it is only enough to exchange the variety of work of the device, having passed to the corresponding scale of the measurement.

When will it check the equipment of chains with the management Ý/m (for example, the system IAC) in the power of launches of tension (4 will see in an illustration the digital Sign) one can be noticed what can be ignored calmly in the analysis of results of the measurement.

It is not necessary also to be bothered in the moment of the emergence of such deformations of the oscillogram like the bevel of the lowest part of the advanced front of rectangular impulses (5 to see values in an illustration the digital Sign) if, naturally, the fact of a vypolazhivaniye of the front will not be a sign of the violation of the usefulness of the functioning of the checked component one.

Frequency

The frequency of the repetition of alarming impulses depends on the frequency of work of a fountain of signs.

The form of the retired sign can be published and be brought to a look, convenient one to the analysis, when there is lighting an oscillograph of the scale of the temporary development of the image.

In the moment of the observation of signs in chains of the alternate current the temporary development of an oscillograph depends on the frequency of fountain of sign (3 sees the variety in an illustration the Analogous sign) determined by motor turns.

I eat already if he said in top, for the reduction of a sign to a legible look it is enough to exchange the scale of the temporary development of an oscillograph.

In certain modifications of characteristic of cases of a sign there are developed especularmente somewhat dependences of reference that is explained by the reversibility of the polarity of the connection of the corresponding element and, the absence of the prohibition of the modification of the polarity of the connection, it can be ignored in the analysis.

Typical signs of component ones of systems of control of the motor

oscillographs modern they are equipped normally of only two alarming wires together with the group of several probes that they allow to execute the connection of the device practically to any device.

The red wire is joined to a safe pole of an oscillograph and one adheres normally to the capture of ECM. The black wire must be joined to the point confiantemente when (weight) was established.

Injectors

The control of the composition of the mixture of air fuel in the modern motorcar the electronic systems of the injection of the fuel practises for the opportune agreement of the duration of the opening of valves eletromagnéticas of injectors.

The duration of the stay of injectors abroach defines for the duration of the developed ECM of the electric impulses happened in an entry valves of Ý/m. The impulses duration normally does not exceed the limit of the variety of 1 ÷ 14 milissegundos.

The typical oscillogram of the impulse undergoes operational operation of an injector in the Injector of Fuel of illustration. Very often in the oscillogram there is possible also to observe series of the short pulsations after straightly the negative rectangular impulse that begins and supporting Ý/m the valve of an injector abroach, and also the sharp positive launch of the tension that accompanies the moment of the close of the valve.

The usefulness of the functioning of ECM can happen easily through an oscillograph for the visual observation of modifications of the form of the operational sign in the moment of a variation of parameters of work of the motor. In this way, the impulses duration in a motor provorachivaniye in the only turns will be lightly higher, of what during the operation of the unity in low turns. The increase in turns of the motor has to result from the corresponding increase in the time of the stay of injectors abroach. This dependence is shown specially well opening a valve of butterfly for the short pressing of the pedal of gas pedal.

The close of Bystry of a valve of butterfly will lead to an oscillogram that levels out confirmation of the fact of an omission of injectors (for systems with a short cut of supply of fuel).

In the coldness departure the motor needs some enrichment of the mixture of air fuel that is provided of the automatic increase in the duration of the opening of injectors. In the process of heating the duration of the operational impulses in the oscillogram it has to be reduced continuously, gradually bringing near the value typical for the only turns.

In systems of the injection in which the injector of the cold departure is not applied in the cold launch of the motor the additional operational impulses that are shown in the oscillogram in the form of pulsations of the variable length are in use.

The typical dependence of the duration of the operational impulses of the opening of injectors in the condition of work of the motor shows up on the table supplied down.

Inductive sensors

The valve of Ø/m of the turns stabilization of wasting time (IAC)

In the car industry the valves IAC eletromagnéticas of the group of several types that give the signs of the form also different are in use.

The common distinctive characteristic of all the valves is the fact that the porosity of a sign will reduce with the increase of the load of the motor joined with the inclusion of the additional consumers of the reduction of motivation of being able in turns of wasting time.

If the porosity of the modifications of oscillogram with the increase in the load, nevertheless in the moment of the inclusion of the consumers' violation of the stability of turns to waste time it happen, checks a condition of a chain of the valve eletromagnética, and also the fairness of the given ECM of a sign of order.

Normally in chains of the stabilization of turns of wasting time the electric step motor polar 4 that the description happens down is in use. The control of valves IAC of 2 contacts and of 3 contacts happens in a similar way, nevertheless oscillograms of the alarming tension given by them they are absolutely differently of.

The electric step motor, resisting the ECM given the sign of functioning of pulsation, does the correction of step of turns of wasting time of the motor according to the temperature of work to cool the liquid and the current load of the motor.

The levels of the operational signs can happen through an oscillograph that will measure of probe if it joins in series an each one of four captures of the step motor.

It tries of lambda (sensor of oxygen)

Sensor of an explosion (KS)

Ignition sign in the exit of the amplifier of ignition

Primary curve of the roll of ignition