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In this article, we discuss apparent “ghost” misfire codes on spark ignition engines in terms of what causes them, as well as talk about misfire detection strategies you may not have known about.

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Ghost Misfire Trouble Codes Explained In theory, it should be easy to diagnose and fix most misfires. After all, proper ignition and combustion in a spark ignition engine require only cylinder compression, fuel, and an ignition source all being present and correct at the right time to complete successfully. So, when one of these things....

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Understanding Forced Induction on Mercedes-Benz M274 M270 Engines: Part 2🤔 End Of Financial Year Hot Redemption Deals!💰 Oscilloscopes Made Easy👌 - https://mailchi.mp/mechanic.com.au/mechanictt19-06-24

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UNDERSTANDING FORCED INDUCTION ON MERCEDES-BENZ M274 / M270 ENGINES: PART 2

In Part 1 of this two-part article, we discussed the general configuration of the forced induction systems on the Mercedes-Benz M274 and M270 family of engines. Now, in Part 2 of this article, we will discuss some common faults and malfunctions that affect the efficient operation of the forced induction systems on these engines, as well as provide some diagnostic tips and tricks that should help you diagnose and resolve the most common forced induction-related trouble codes on M274 and M270 engines. Let us start by listing-

THE MOST COMMON SYMPTOMS AND TROUBLE CODES YOU’RE LIKELY TO SEE

The most common symptoms of forced induction system failures and malfunctions are largely similar across all applications but note that not all forced induction system-related malfunctions always produce fault codes. Nonetheless, some common symptoms include-

varying degrees of power at some or all engine speeds
increased fuel consumption
increased oil consumption
rough engine running at some or all engine speeds
a general complaint that the vehicle is not as responsive to throttle inputs as it used to be

These kinds of complaints are usually, but not always, the result of one or more of the fault codes listed below-

P029900 – “The boost pressure of turbocharger 1 is too low”
This code usually indicates a mechanical failure of the turbocharger or one or more associated components.

P029909 – “The boost pressure of turbocharger 1 is too low”
This code indicates a failure of or malfunction in a component in the forced induction system that the engine management system cannot identify.

P029921 - “The boost pressure of turbocharger 1 is too low”
This code means that the amplitude of the signal generated by the boost pressure transducer is lower than the minimum allowable signal amplitude. Note that while this usually indicates an actual under-boost condition, this code could also indicate a defective or malfunctioning boost pressure transducer.

P023422 – “The boost pressure of turbocharger 1 is too high”
This code means that the amplitude of the signal generated by the boost pressure transducer is higher than the maximum allowable signal amplitude. Note that while this usually indicates an actual over-boost condition, this code could also indicate a defective or malfunctioning boost pressure transducer.

As a practical matter, the four trouble codes listed here cover a lot of ground in terms of their possible root causes and fixes, but before we get to specifics, note the following-

Although it is possible to diagnose the codes listed above (and others) without using Mercedes-Benz's Xentry diagnostic software, you will need a very high-end generic scan tool that a) can access all the control modules in the vehicle, and b) have bi-directional control functions. This is required because some components, such as the turbocharger's wastegate actuator can only be tested with a capable scan tool.

However, the advantage of using the Xentry diagnostic system is that the scan tool displays step-by-step diagnostic plans that almost resemble diagnostic flow charts, but in significantly more detail. If you do not have access to Xentry software, we strongly suggest that you obtain relevant Mercedes-Benz OEM service and repair information, including relevant wiring diagrams, pin-out charts, and the latest TSBs from the manufacturer to complement a generic scan tool’s abilities.

Having said the above, let us look at-

THE FAULTS YOU ARE MOST LIKELY TO ENCOUNTER

The network of vacuum lines that control the boost pressure is rather extensive, and it is often impossible to find or locate small vacuum leaks that can potentially affect the operation of the boost control system. Consider the diagram below-

Image source: https://automotivetechinfo.com/wp-content/uploads/2024/01/vacuum.jpg

The vacuum lines rendered in yellow (indicated by the red and green arrows) in this view may be the most accessible part of the vacuum system, but these lines are also the most likely to develop leaks because they are the most exposed to heat and vibration. Moreover, because they are routed so close to the engine, these lines are also susceptible to damage and perforation caused by chafing and rubbing against some engine components.

In older vehicles, these lines often develop hairline cracks and splits that are extremely difficult to locate without a heavy-duty smoke machine, or better still, a vacuum pump fitted with an accurate vacuum gauge, but checking and testing these vacuum lines to verify their integrity is always a useful starting point when diagnosing any forced induction system related codes on M274 and M270 engines.

Bear in mind that there are no known ways of repairing leaks in these lines that will last more than a few days or more commonly, only a few hours. The only reliable way of resolving leaks in these lines is to replace them with OEM or OEM-equivalent parts, along with all seals, grommets, and retaining clips, which brings us to-

PRESSURE SENSOR ISSUES

In the previous article, we mentioned the fact that the forced induction system on M274 and M270 engines use two intake air pressure sensors- one immediately upstream of the throttle body, and another immediately downstream of the throttle body to produce more accurate readings of the air entering the engine.

So while the two pressure sensors will produce different readings when the engine is running, there is no air entering the engine when the engine does not run. Therefore, the two sensors should both register atmospheric pressure under KOEO (Key ON Engine Off) conditions and while it is rare to see two sensors registering exactly the same values, the difference between the two readings should not exceed about one per cent. If the two sensors generate readings that differ by more than about one per cent, one sensor (or sometimes both sensors) is/are defective.

However, be sure to obtain the current atmospheric pressure at your location from a reliable source such as your local weather station or airport before condemning one or both pressure sensors. Both sensors might be defective, albeit not always to the same degree, and so the engine management system will act on two erroneous readings, which will greatly affect the boost pressure.

BOOST PRESSURE TRANSDUCER ISSUES

Image source: https://automotivetechinfo.com/wp-content/uploads/2024/01/mb-control-rod.jpg

This image shows the turbocharger waste gate’s vacuum actuator (indicated by the red arrow), which can fail to work as expected for several reasons. The two-headed black arrow indicates the control rod’s direction(s) of travel, which should always be equal in both directions.

However, the three most common reasons why the wastegate or its actuator might fail to work correctly are-

an excessive build-up of carbon inside the turbocharger that prevents the wastegate from opening or closing fully. Depending on the nature of the problem, you will see either a chronic boost or a chronic over-boost condition
a ruptured or perforated actuator diaphragm
an insufficient vacuum supply to the actuator

Note that, unlike other vehicles, on which it is often possible to move the control rod by hand to test its operation, this should never be done on any Mercedes-Benz engine because doing so could, and often does a) damage the vacuum actuator, and/or b) disturb/change the control rod’s adjustment setting.

The only way to test the operation of the actuator is to follow OEM service information to activate the vacuum system with a capable scan tool’s bi-directional function. Not following OEM-specified procedures during this test usually produces false, misleading, or inconclusive test results. For example, not using a calibrated vacuum gauge to check and verify that the boost pressure control transducer does pass vacuum while testing the wastegate actuator, may result in the wastegate actuator not working because the transducer is not allowing vacuum to pass through it.

VACUUM PUMP ISSUES

Image source; https://automotivetechinfo.com/wp-content/uploads/2024/01/boost-vacuum-circuit.jpg

This schematic shows the location of the engine-driven vacuum pump (circled in red) that supplies both the boost control and brake systems with a constant vacuum that is independent of the engine speed.

It should be noted that a reduced vacuum has a direct effect on both the brake and boost control systems, but what is more important to bear in mind is that vacuum pump failures resulting from oil contamination or mechanical failure are fairly common on M274 and M270 engines.

In practice, a new vacuum pump, or a vacuum pump that is in good mechanical condition will typically produce a vacuum of 28 inches of Mercury, which is equal to 950 mBar. However, it is rare to see a well-used vacuum pump producing a negative pressure of 950 mBar, but that is not necessarily an issue because Mercedes-Benz service information specifies a minimum allowable vacuum of 750 mBar.

So if the wastegate does not work as expected, be sure to take a reading of the vacuum the pump produces at the pump’s small outlet. If you find a vacuum of less than 750 mBar, remove the pump's cover to inspect it for evidence of engine oil contamination. Assessing mechanical damage is a little more difficult to do, but in all cases, the pump must be replaced if the vacuum it produces is less than the specified minimum.

On the other hand, if the pump produces an acceptable vacuum, inspect all the vacuum lines as well as all vacuum line junctions/joints for signs of damage and leaks that could affect the correct operation of the overall boost pressure control system.

PRESSURE BY-PASS VALVE ISSUES

As a prac5ical matter, the air by-pas valve is mounted on the intake side of the turbocharger and it acts like a mini dump valve to relieve excess pressure and violently oscillating pressure waves that develop around the compressor wheel and in air intake during deceleration.

This action reduces large fluctuations in the rotating assembly’s rotational speed during normal engine operation and as such, it reduces turbo lag significantly during large throttle inputs. However, the problem with the air by-pass valve is that it does not necessarily set fault codes when it fails or stops working as it should, which also does not necessarily produce noticeable drivability symptoms.

Moreover, the calibrations of air bypass valves are engine-specific, meaning that different engines within the M274/M270 family have air bypass valves that are calibrated differently. Therefore, be sure to consult OEM service information for details on how to test and assess the condition of the air by-pass valve in all cases where forced induction system-related fault codes are present on an affected vehicle. Failing to verify that the bypass valve works as expected can produce misleading, inconclusive, or downright wrong diagnoses for a variety of forced induction issues, which leaves us with this-

CONCLUSION

We hope that this article has given you some new insights into the forced induction systems of the M274/M270 family of Mercedes-Benz engines. Having said that, we must also stress the need for you to be sure of your diagnoses, because making a misdiagnosis, even inadvertently, could potentially have huge financial implications for you and your employer.

For example, some components, such as waste gates and wastegate actuators are not available separately. This means that replacing these components requires replacing the entire turbocharger/exhaust manifold assembly, which is a hugely expensive exercise. Not that any of us would make a misdiagnosis intentionally, but we are only human and we all make mistakes.

Therefore, to avoid making mistakes when diagnosing forced induction faults on M274 and M270 engines, we highly recommend that you a) obtain the relevant service information and b) study it carefully before you attempt a diagnosis. We say that not because the forced induction systems on Mercedes-Benz engines are inherently complicated but because making a mistake while diagnosing a Mercedes-Benz forced induction system could lead to very costly mistakes.

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In Part 2 of this article, we discuss some common faults and malfunctions that affect the efficient operation of the forced induction systems on Mercedes-Benz M274 and M270 engines.

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Understanding Forced Induction on Mercedes-Benz M274 / M270 Engines: Part 2 In Part 1 of this two-part article, we discussed the general configuration of the forced induction systems on the Mercedes-Benz M274 and M270 family of engines. Now, in Part 2 of this article, we will discuss some common faults and malfunctions that affect the efficient operation of the forced induc...

What brand is this car? Easy edition!

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In case you missed it ...
OSCILLOSCOPES MADE EASY

An old truism holds that “a little knowledge can be a dangerous thing”, especially from our perspective as mechanics and technicians, since we both require, and use or process large amounts of data/information/knowledge to draw valid diagnostic conclusions, or to make reasonable inferences when we formulate diagnostic strategies. However, in the context of the car repair industry, the opposite is often also true because too much knowledge/data/information can, and often does, obfuscate the problems we are trying to diagnose and resolve on our customers’ vehicles.

All of us have been in situations where we had to decide which of several possible diagnostic paths to follow, some of which often lead nowhere, diagnostically speaking. Thus, in this article, we explain how to avoid following unproductive diagnostic paths by using a digital storage oscilloscope, since an oscilloscope will almost always point you in the right diagnostic direction by providing only the information you need, as opposed to all the information you would like to have. Before we get to the specifics of oscilloscopes, and why you need to use one more often, though, let us look at-

THE PROBLEM WITH COLLECTING DIAGNOSTIC INFORMATION

All of us own an arsenal of diagnostic equipment that usually includes one or more scan tools, sensor simulators, relay testers, breakout boxes, current probes/testers, a variety of amp clamps, and one or more digital multimeters, and all of these tools have their legitimate uses. In fact, we could not do our jobs effectively without these tools, but on the other hand, throwing all these tools at (some) diagnostic challenges simultaneously often creates a kind of “Which came first, the chicken or the egg?” situation.

Diagnosing communication codes is a good case in point. For instance, even if we use a scan tool that can a) display the layout of a serial communications system, and b) indicate which modules are not communicating, we have no way of telling what had caused the communications issue until we find the actual problem. This is an example of the chicken-or-the-egg situation; did a control module fail, or was there a wiring failure that necessarily affected one or more control modules’ ability to communicate?

So, as a practical matter, the problem we all have with gathering diagnostic information is that we often don’t know what is causing a problem, and as a result, we often don’t recognize the point at which we have gathered sufficient information to diagnose and fix the problem.

So how do we know we have sufficient information to diagnose and fix a problem on vehicles we have not seen before? If the truth were told, we often don’t know, but this article does not intend to teach anyone how to formulate a viable diagnostic plan or strategy. Nonetheless, this writer would like to suggest that there is an easy way to cut through the (diagnostic) white noise to extract just the information we need, as opposed to gathering all the information we possibly can- much of which sometimes obfuscates the problem we are trying to diagnose, so let us consider-

ANOTHER WAY OF GATHERING DIAGNOSTIC INFORMATION

If you are new to the car repair industry, you probably have not yet fully appreciated the facts that a) all cars largely work in the same way, b) that similar failures on all cars occur for largely the same reasons, and c) that the basic laws of physics and electricity do not change between vehicle makes and models.

So what does this mean in practice? It means that in terms of the scientific laws and principles that underpin the control systems of all modern vehicles, there are more similarities between vehicle makes* and models than there are differences- despite the differences in the technical implementation of some systems that exist between vehicle makes and models.

*Note that electric and hybrid vehicles are excluded from this statement. While a similar principle applies to both categories of vehicles, both vehicle categories are sufficiently different from conventional vehicles to require specialized training, equipment, and skills to work on their high-voltage systems.

At the risk of overstating the case, we can expand the above statement a bit further by saying that apart from their outward appearance(s), there are no material differences between modern vehicles. All contain largely the same components that are assembled to largely the same pattern, and all rely on electricity to make the vast majority of their components work as designed.

So, how does any of the above helps us? It’s simple really; if we think about the above statements objectively, it should be obvious that since all conventional vehicles work in much the same way, we should be able to use a single piece of diagnostic equipment to diagnose a large percentage of issues on all vehicles by following largely the same processes and principles, and we can do just that with a digital storage oscilloscope.

Of course, the proverbial devil always lives in the details, and in this case, the details involve having to learn how to interpret waveforms, which are visual representations of how electrical currents are flowing to, from, and through components like actuators, motors, sensors, rheostats, and the like.

However, the upside of waveforms is that (among others) things like spark events, CAN system operation, sensor outputs, and current draws all produce the same type of waveform, regardless of the vehicle they were taken from. The practical advantage of this is that if we investigate something like for example, a misfire, we can obtain a visual representation of the spark event in the form of a waveform that we can analyse and compare to waveforms taken from cylinders that are not misfiring.

Such an analysis can save a lot of diagnostic time, so let us take a closer look at how to use a-

DIGITAL STORAGE OSCILLOSCOPES, THE (NEAR) ULTIMATE DIAGNOSTIC TOOL

This writer has often heard even experienced technicians say that oscilloscopes are difficult to use, and the data (waveforms) they produce are almost impossible to interpret and understand, but nothing could be further from the truth. Of course, learning to use an oscilloscope effectively involves a rather steep learning curve, but we deal with learning curves almost daily in our careers, so learning how to use an oscilloscope should not present anybody with undue difficulties.

However, as a practical matter, it is easy to remove much of the guesswork involved with using oscilloscopes simply by understanding how these instruments work, knowing what their limitations are, and how to overcome most limitations by understanding and exploiting the abilities of any given instrument. This statement may appear to be confusing and contradictory, but let us reduce it to a simpler form by explaining-
THE CONCEPT OF WAVEFORMS

In case you were wondering, there is nothing particularly “clever” or scientific about the word “waveform”; the word has become a kind of catch-all reference to the data, which in this case, is the line on the oscilloscope screen. This particular example is an actual waveform of a single beat of a person’s heart, which incidentally, somewhat resembles the shape (waveform) of a spark event in a spark ignition engine.

Nonetheless, it does not matter if a waveform is created by a human heart, or by the secondary ignition system of a vehicle; both the heart and the ignition system work with electricity, which is what an oscilloscope uses to create the lines we know as waveforms.

As a practical matter, though, all oscilloscopes measure the difference in electrical potential between two test leads; the amplitude (height) of the waveform represents the intensity of the difference in potential, while the horizontal distance between the peaks of the waves represents the frequency of the signal over time. In this example, the flat lines on either side of the actual signal represent no measurable activity in the circuit being tested.

While this example shows only a single signal, single signals typically convey no useful diagnostic information on vehicles, unless the single signal being analyzed is an extract of a larger signal. Consider the image below-

Image source: https://www.vehicleservicepros.com/service-repair/diagnostics-and-drivability/article/21260131/the-king-of-all-diagnostic-tools-and-how-to-use-it

This example shows a waveform created by a cranking V8 engine during a relative compression test. This type is waveform is known as a repetitive capture since it shows several engine cycles that were recorded consecutively. Let us look at what this example shows, exactly.

Note that the screen is divided into six equal divisions and that the blue scope trace descends sharply in the first division. This part of the trace indicates the sharply decreasing battery amperage as the starter motor works to overcome the inertia of the stationary engine.

The following five divisions each represent 720 degrees of crankshaft rotation or one engine cycle, and each peak in each division represents the amperage draw of each cylinder during its compression stroke. Since it takes more power (current) to rotate the engine through each cylinder's compression stroke than it takes to rotate the engine through the other strokes that offer no resistance to the movement of the piston, each compression stroke is represented here by a peak in current draw.

This type of test is typically done by attaching an amp clamp around the positive battery cable, but the object at this point is not to identify which cylinder is misfiring; the object of this test is to see if all the cylinders develop the same level of compression pressure. If they do, all the peaks in this waveform would have the same height, since it would take the same amount of current to rotate each cylinder through its compressions stroke, but since these peaks do not have the same height, what are we looking at in this example? Consider the image below-

Image source: https://www.vehicleservicepros.com/service-repair/diagnostics-and-drivability/article/21260131/the-king-of-all-diagnostic-tools-and-how-to-use-it

This image is a zoomed-in view of one division, or one engine cycle that was obtained by using moveable horizontal and vertical cursors to both measure the actual current draw of the cylinders and to define a single engine cycle. Note the small irregularities in each wave; these small peaks and valleys were created by small deviations in the current flow and typically indicate the added effort required to rotate camshafts and other valve train components. Depending on the abilities of the oscilloscope being used, it is possible to zoom into a single cylinder’s current draw profile to identify the points in the piston’s movement where the valves open and close with great precision.

Nonetheless, in this example, we are only interested in comparing the compression pressures in the cylinders. Note the dotted cursor line that starts at the extreme left; this line connects to a scale (not shown here) that indicates that one cylinder draws 181 amps, while the subsequent cylinders all draw significantly less, with the smallest draw being only 152 amps.

Although this does not identify the cylinders with the highest and lowest compression pressures, the most likely cause(s) of this pattern are a) excessive ring wear in most cylinders that causes excessive cylinder blowby or b), leaking valves that dump compression pressure into the exhaust system or intake manifold. While this type of compression difference between cylinders could also be caused by blown cylinder head gaskets, this is unlikely because damaged head gaskets typically produce smaller pressure differences than seen in this example.

Moreover, a relative compression test as shown in this example is definitive proof that this particular engine is suffering from mechanical issues, as opposed to electrical issues that typically do not produce differences in compression pressure between cylinders. Nonetheless, this particular diagnosis can be further refined by connecting a suitable pressure transducer (that converts pressure waves into electrical signals to either the exhaust outlet or the intake manifold. If the intake valves were leaking, the pressure waves in the intake manifold would correlate strongly with the relative compression test waveform. If, on the other hand, the exhaust valves were leaking, the pressure waves in the exhaust would also show a strong correlation to the relative compression waveform.

Similarly, if there were excessive cylinder blowby, a transducer connected to the oil filler hole in the valve cover would produce a waveform that will also show a strong correlation with the relative compression test waveform.

It is important to note though that “strong correlation” in this context does not translate into “match exactly”, because in some cases, some parts of the waveforms may be inverted relative to the compression test waveform. For instance, the cylinder with the highest compression pressure will leak the least, meaning that the pressure peak for that cylinder at the exhaust or intake manifold will be the lowest, which begs this question-

HOW ACCURATE ARE OSCILLOSCOPE TEST RESULTS?

Although tests like the above are 100 per cent accurate when performed by a skilled operator, the amount of usable diagnostic data that all waveforms contain varies in direct proportion not only to the operator’s skill in terms of interpreting the obtained data but also in proportion to the abilities and capacity of the instrument being used. In a practical sense, it is impossible to overstate the importance of an oscilloscope’s limitations being considered in all tests, so let us look at-

OSCILLOSCOPE SAMPLING RATES

Since oscilloscopes work by measuring and displaying electrical impulses over time, an oscilloscope’s sampling rate is an indication of how many impulses it can measure and display over time, which is typically expressed in seconds. One other critical parameter is an oscilloscope’s available memory, which determines how many samples are stored, and how many are simply dumped or deleted during the production of usable waveforms.

However, few, if any inputs derived from automotive components will ever overwhelm the memory capacity of an oscilloscope that is designed for use in the automotive industry, so for our purposes, we will focus only on sampling rates. This is a highly technical subject and most of the finer details fall outside the scope of this article, but for automotive applications, an oscilloscope should ideally have to ability to capture and process samples at a rate that is at least twice as high as the highest rate at which a component can generate samples. Put differently, this means that if something like say, a throttle control stepper motor can generate samples at a speed of 1000 (samples) per second, you’ll need an instrument that can process that number of samples in 0,5 seconds (double the sample generation rate) to produce a stable and useable waveform.

Fortunately, though, the designers of oscilloscopes intended for use in the automotive industry know this, and all modern automotive oscilloscopes can cope with any sampling speed almost any automotive component(s) can generate, so we don’t have to spend too much time discussing this aspect of oscilloscope design. Nonetheless, and despite the above, consider the image below-

Image source: https://www.vehicleservicepros.com/service-repair/diagnostics-and-drivability/article/21260131/the-king-of-all-diagnostic-tools-and-how-to-use-it

Sadly, not all oscilloscopes sold in the automotive repair industry are designed to internationally accepted standards and norms. These instruments are mainly incorporated into many cheap generic scan tools that are made in the Far East, but are also offered as stand-alone, “competitively priced” oscilloscopes on many online retail sites.

The image above shows a generic representation of a waveform that could have been taken with such an oscilloscope; i.e., one that could not process the samples the component being tested produced. In this example, the speed/second of the incoming samples overwhelmed the instrument’s memory, and as a result, it simply dumped or deleted those samples, which are represented here by the red part of the waveform.

Essentially, the red part of the waveform is lost data that could have contained valuable diagnostic data. As it happened, however, the instrument simply dumped consecutive samples until it was able to catch up, at which point it resumed producing a usable waveform. Depending on the magnitude of variations in the speed of the incoming samples, this pattern of lost data can/will be repeated every time the instrument’s memory is overwhelmed, which renders instruments like this useless for performing modern diagnostics, which raises the question of-

WHICH OSCILLOSCOPE TO BUY?

Given the fact that many diagnoses that would ordinarily have taken many hours to make can be made within minutes by using an oscilloscope intelligently, the best advice this writer can give anyone is to buy the best instrument that is available, as opposed to buying the best-priced instrument.

On the other hand, there is no point in buying an instrument that is best suited for use in an aerospace research facility for many thousands of dollars. Instead, one long-established supplier of oscilloscopes and related equipment to the global automotive industry sells only the software that turns a (new-ish) laptop computer (that you likely already own) into an advanced oscilloscope at very reasonable prices.

Moreover, this supplier also offers users of their products access to a vast library of known-good and known-bad waveforms that cover most faults on the vehicles we in the independent repair industry typically see in our bays, which saves you the trouble of learning how to figure out what a waveform is trying to tell you.

In addition, a reasonable subscription also gives you access to a community of thousands of experienced oscilloscope users from all over the world that are always ready to offer help, advice, and diagnostic insights as well as the ability to upload your own waveforms for the benefit of other users elsewhere in the world. If that is not enough, you can also get access to a huge number of guided tests that show you how to connect your oscilloscope to almost any component on most of the vehicles we see daily, which leaves us with this-

CONCLUSION

This article barely scratched the surface of the topic of how and why we should all use oscilloscopes more frequently, and while we only reference one example of how to cut down on diagnostic time, the fact is that there is almost no component on modern vehicles whose operation that cannot be checked, or diagnosed with oscilloscope waveforms.

We can list a few more examples here. We could, for instance, check the operation of CAN systems in minutes simply by connecting to the DLC instead of spending days unplugging control modules, and checking wiring. We could also make simple connections to an ignition system to check the operation of ignition coils, ignition driver circuits, and spark plugs, while using a second and third channel on the oscilloscope to verify ignition timing and actual fuel pressures, respectively, at the same time. Then again, we can also check and verify the operation of drive-by-wire throttle control systems, as well as check and verify the operation of oil control solenoids in variable valve timing systems, among many other control functions.

Note however that the above is not the same as saying that an oscilloscope can, or should replace all the diagnostic and test equipment we already own- far from it. Nevertheless, using an oscilloscope to narrow down the possible causes of most failures and defects will not only save you many hours of chasing down faults by other means, but it will also greatly reduce the number of times that you start down the wrong diagnostic path- as happens to some of us on occasion.

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