Saab 9-5

It is not necessary to worry also at occurrence of such deformations of the oscillogram, as скашивание the bottom part of forward front of rectangular impulses (5 values see an illustration the Digital signal) if, of course, the fact выполаживания front is not a sign of infringement of serviceability of functioning of a checked component.

Frequency

Frequency of repetition of alarm impulses depends on working frequency of a source of signals.

The form of a removed signal can be edited and led to a kind convenient for the analysis by switching on an oscillograph of scale of time development of the image.

At supervision of signals in alternating current chains time development of an oscillograph depends on frequency of a source of a signal (on an illustration the Analog signal), defined by engine turns.

As already it was told above, for signal reduction to a legible kind it is enough to switch scale of time development of an oscillograph.

In certain cases characteristic changes of a signal appear developed mirror concerning reference dependences that speaks реверсивностью polarity of connection of a corresponding element and, in the absence of an interdiction for change of polarity of connection, can be ignored at the analysis.

Typical signals of components of control systems of the engine

Modern oscillographs are usually equipped by two alarm wires in a compartment with a set various щупов, allowing to carry out device connection practically to any device.

The red wire is connected to a positive pole of an oscillograph and usually connected to plug ECM. The black wire should be connected to reliably earthed point (weight).

Injectors

Management of structure of an air-fuel mix in modern automobile electronic systems of injection of fuel is carried out by timely updating of duration of opening of electromagnetic valves of injectors.

Duration of stay of injectors abroach is defined by duration developed ECM the electric impulses submitted on an input э/м of valves. Duration of impulses usually does not fall outside the limits a range 1 - 14 мс.

The typical oscillogram of the impulse operating operation of an injector, is presented on an illustration a fuel Injector. Often on the oscillogram it is possible to observe also a series of the short pulsations following directly behind the initiating negative rectangular impulse and supporting э/м the valve of an injector abroach, and also the sharp positive throw of pressure accompanying the moment of closing of the valve.

Serviceability of functioning ECM can be checked easily up by means of an oscillograph by visual supervision of changes of the form of an operating signal at a variation of working parametres of the engine. So, duration of impulses at проворачивании the engine on single turns should be a little above, than at unit work on low turns. Increase of turns of the engine should be accompanied by respective increase in time of stay of injectors abroach. The given dependence is especially well shown at opening throttle заслонки by short pressing a gas pedal.

By means of thin щупа connect a red wire of an oscillograph to инжекторной to plug ECM. Щуп the second alarm wire (black) oscillograph reliably earth.

Analyse the form read out during time проворачивания the signal engine.

Having started the engine, check up the form of an operating signal on single turns.

Sharply having pressed a gas pedal, lift frequency of rotation of the engine to 3000 rpm, - duration of operating impulses at the moment of an acceleration should increase considerably, with the subsequent stabilisation at the level equal, or hardly smaller peculiar to idling turns.

Fast closing throttle заслонки should lead to the flattening of the oscillogram confirming the fact перекрывания of injectors (for systems with отсечкой fuel givings).

At cold start the engine requires some enrichment of an air-fuel mix that is provided with automatic increase in duration of opening of injectors. In process of warming up duration of operating impulses on the oscillogram should be reduced continuously, gradually coming nearer to value typical for single turns.

In injection systems in which the injector of cold start is not applied, at cold start of the engine the additional operating impulses shown on the oscillogram in the form of pulsations of variable length are used.

In the table resulted more low typical dependence of duration of operating impulses of opening of injectors on a working condition of the engine is presented.

Inductive gauges

Start the engine and compare the oscillogram removed from an exit of the inductive gauge with reference, resulted on illustration.

Signal of the inductive gauge

The increase in turns of the engine should be accompanied by increase in amplitude of a pulse signal developed by the gauge.

Ljambda-probe (the oxygen gauge)

Connect an oscillograph between the ljambda-probe plug on ECM and weight.

Make sure that the engine is heated-up to normal working temperature.

Compare the oscillogram displayed a measuring instrument with reference, resulted on an illustration the Ljambda-probe.

If the removed signal is not wavy, and represents linear dependence, that, depending on pressure level, it testifies to excessive repauperization (0 - 0.15), or reenrichment (0.6 - 1) an air-fuel mix.

If on single turns of the engine the normal wavy signal takes place, try to squeeze out sharply some times педель gas, - signal fluctuations should not fall outside the limits a range 0 - 1 Century

The increase in turns of the engine should be accompanied by increase of amplitude of a signal, reduction - decrease.

Ignition signal on an exit of the module of ignition

Connect an oscillograph between the plug of the module of ignition on ECM and weight.

Warm up the engine to normal working temperature and leave its working on single turns.

On the oscillograph screen the sequence of rectangular impulses of a direct current should stand out. Compare the form of an accepted signal with reference, paying steadfast attention to coincidence of such parametres, as amplitude, frequency and the form of impulses.

Operating signal of the module of ignition

At increase in turns of the engine frequency of a signal should increase in direct ratio.

Primary winding of the coil of ignition

Connect an oscillograph between the plug of the coil of ignition and weight.

Warm up the engine to normal working temperature and leave its working on single turns.

Compare the form of an accepted signal with reference, resulted on an illustration the Primary winding of the coil of ignition, - positive throws of pressure should have constant amplitude.

Non-uniformity of throws can be caused excessive resistance of a secondary winding, and also malfunction В/В of a wire of the coil.