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Signs of a malfunctioning knock sensor on a Magentis cue. Knock sensor. Knock sensor diagnostics

Despite the fact that car service services are now available anywhere in the country at any time of the day, a car enthusiast still needs to know the structure of his own car, he needs to be “friends” with it. There are no small details in the design of a car, and even the smallest parts sometimes carry a serious functional load, affecting the performance characteristics of critical units and systems.

We are talking about sensors - miniature devices that remove information about the operating modes of individual technical devices and units of the car at each current moment and transmit it to the “brain” of the car - the ECM (electronic engine control system). Based on the signals read from each of the sensors, and there are more than a dozen of them in the design of the VAZ 2114, the ECM can control and optimize the parameters of the corresponding parts of the engine and the machine elements driven by it. For example, the knock sensor included, among others, in the basic configuration of the VAZ 2114 car, is characterized by the following distinctive features:

The knock sensor (DS) performs one of the most important functions in this complex organism. It is this sensor that monitors engine operation for the occurrence of detonation and its degree, and even recognizes the causes and nature of this undesirable phenomenon. Thanks to the operation of the DD, the control system can promptly correct the characteristics that caused detonation.
The location where the knock sensor is located on the VAZ 2114 provides the ability to immediately respond to the appearance of detonation in any engine cylinder. The knock sensor is located directly on the engine block between the cylinders (second and third) on the radiator side. This place is inconvenient for access, but the DD has a simple and reliable design, and therefore rarely fails. The VAZ 2114 uses both resonant and broadband sensors, with one or two working contacts.
The operating principle of the knock sensor is based on the well-known reaction of the piezoelectric effect. That is, the basis of the sensor is a piezoelectric plate, which begins to generate electricity from the moment the detonation vibrations occur, the voltage is higher, the higher the frequency of oscillatory movements. The voltage from the DD is transmitted to the control unit, which automatically adjusts the ignition timing setting and subsequently adjusts the ignition reaction of the air-fuel mixture.

A little about the phenomenon of detonation

In order to understand in detail why a knock sensor is needed on a VAZ 2114, let’s first talk about the phenomenon of detonation itself and the reasons for its occurrence. The external manifestation of detonation is characteristic metallic sounds, which are referred to as “fingers knocking.” But in fact, detonation occurs due to an imbalance in the parameters of the fuel combustion process and the ignition timing, as a result of which the temperature and pressure inside the combustion chamber increase many times over, which leads to micro-explosions of the self-ignited combustible mixture, giving the effect of metal knocking on metal.

Now that it has become clear what the knock sensor is used for, we can name the main reasons for the appearance of detonation in the VAZ 2114 engine:

The quality of gasoline, its brand. The lower the octane number of gasoline (brand), the less knock-resistant it is.
Inaccuracy in setting the ignition timing. To identify it, you need to check the values of the maximum and static ignition timing angles. Such a defect can cause serious malfunctions, including errors in determining detonation. In this case, you already need to check how the knock sensor works.
Increasing the combustion temperature of the working mixture due to depletion of its composition. A lean mixture initiates the detonation process by reducing fuel evaporation and, as a result, reducing the amount of heat absorbed. Because of this, the temperature rises sharply and detonation occurs. Visually, a sign of a lean mixture can be determined by deposits on the spark plugs.
The presence of any malfunction that increases the back pressure in the system prevents the exit of hot gases from the combustion chamber, thereby contributing to the development of detonation oscillations.
Critical operating conditions of the engine (composition of the working fuel mixture used, excess of the load on the engine permissible by technical conditions, carbon deposits on the combustion chamber elements, hot climatic conditions, etc.)

The phenomenon of detonation, accompanied by overheating of engine elements, in particular the crank mechanism, reduces the wear resistance of parts from time to time, causing serious damage, and then the final failure of the car engine.

If the knock sensor is faulty

It happens that the DD starts producing strange errors, or the engine is heard shaking, which means that you urgently need to diagnose the sensor. You should first inspect the supply wiring, check the condition of the contacts, and clean them if necessary. If no problems are found, then the sensor itself is faulty. Diagnostic measures can be performed independently; they are carried out in the following sequence:

remove the sensor from its installation location using socket wrenches of standard sizes “13” or “20”, depending on the specific type of sensor;
set the voltmeter to an operating mode within 200 MV and connect the ends of the knock sensor wiring to it
slowly tap the sensor body with a screwdriver several times, changing the impact force and frequency, and observing the voltmeter readings. The absence of a response from the measuring device will indicate a malfunction of the sensor.

You can buy a knock sensor for a VAZ 2114 at any retail outlet that sells automobile spare parts. In order not to make a mistake in your choice, you must inspect the sensor that was previously installed on the car, or it is better to take it with you. When purchasing a knock sensor, you need to make sure that the device you are purchasing is of high quality from a serious manufacturer, because normally it should have a long service life. By the way, the price of a VAZ 2114 knock sensor is quite low - domestic ones cost around 250 rubles, and imported ones, from Bosch, range from 220 to 500 rubles.

The knock sensor on the VAZ 2114, despite its very modest size, very simple design and low cost, performs a very important mission - it protects the engine from the prospect of slow destruction. Without this device, it would be simply impossible to operate cars normally.

The engine management system is a complex electronic mechanism, part of which is the knock sensor. Problems with the sensor do not interfere with engine operation, but lead to unpleasant consequences. That's why it's worth studying signs of a malfunctioning knock sensor to make repairs on time. We will describe how to do this below.

What is a knock sensor and why is it needed?

This part is found in cars that use gasoline as fuel. It is intended for injection types of engines. The sensor is located on the engine cylinder block. This is an important part of the control system, the main purpose of which is to control the level of detonation.

In answering the question, it should be noted that thanks to it the following capabilities of the car are realized:

Fuel economy.
The ability of the engine to develop maximum power.

Detonation is the electrical impulse created during ignition. It is thanks to detonation that the car starts, complex chemical and physical processes occur inside the engine, and the fuel ignites.

The sensor monitors the vehicle's starting system and regulates its proper operation.

What are the main components of a knock sensor?

The main details of this mechanism are:

Vibrating plate.
Piezo type electrical element.
Signal wire.
Braid.

Where is the knock sensor located?

Depending on the make of the car, the location of the sensor may vary, but it is always located on the engine body. The part itself is very small, about the size of a matchbox.

Part installation features

An important feature of installing the sensor is the presence of an electronic ignition system in the car. If it is not there, then there is no sensor. Older models do not have a knock sensor. It is also not installed on carburetor engine systems.

The sensor operation of a modern car is displayed on an electronic panel in the cabin. If there is a malfunction, the car owner will immediately notice it.

Replacing the sensor on a VAZ, video:

Sensor operation

There is an icon on the car dashboard "Check". In English this translates as check or control. If it is not active, then the knock sensor is working and working as expected.

Operating principle of the knock sensor enclosed in a piezomechanism. There is a plate with a piezo effect inside the sensor. When detonation occurs, voltage is created at the input and output, and the engine vibrates. Otherwise, this is called the creation of a potential difference. If the voltage level at one end is too high, the sensor corrects this process.

If for any reason the sensor breaks down, the icon will light up on the dashboard "Check". This will mean only one thing: urgent repair or replacement of the element is required.

Experienced car enthusiasts can detect by sound the presence of a malfunction in this mechanism, but if there is an electronic system, this is not necessary to know.

If the electrical circuit of the sensor is not broken, but a breakdown exists, the “Check” icon will not light up. Therefore, it is worth listening to your car sometimes.

How to check the knock sensor?

Unfortunately, the knock sensor can also fail. In this case, a person without special knowledge will be able to notice this only by the lit indicator. No other obvious signs will be noticed. The car will continue to operate in the same mode and start without any signs of breakdown.

At this point, it is necessary to remember that this device is not mechanical, it is part of an electronic system, and therefore the breakdown is considered electronic.

Knock sensor malfunction can happen for a number of different reasons, including:

There has been a breakdown inside the sensor itself.
Closure.
The signal wire or braided shield is broken.
Damage to the engine control unit.

Thus, it will not be difficult to identify the breakdown. In order to determine it, it is necessary to conduct a test.

The easiest way to check is to go to a car service center. There, experienced craftsmen will open the engine protection and identify the breakdown in just an hour.

But those who are not looking for easy ways can always carry out this simple process on their own. Self-checking occurs according to the following scheme:

First, we remove the protection in the garage. You will have to work directly with the engine block.
Now we rule out a break in the signal wire and shielding braid. If it is torn or the braid is torn, you need to check the fastening of the plug and socket of the sensor. The integrity of the braid must be checked.
If a break is excluded, the outlet itself is assessed. It is possible that its connection is faulty and requires replacement.
You can detect faults in the device itself using a voltmeter. In this case, the car must be started and idling.
You also need to check the condition of the device contacts.

You can check it yourself in a slightly different way. For this you need a multimeter. This device is very often found among car enthusiasts.

Multimeter is a combined device that combines the functions of an ohmmeter, ammeter and voltmeter. You can use either a mechanical or an electronic device.

Checking the knock sensor with a multimeter performed only after it has been removed from the engine. When checking, they knock on it with something metal. This method is the simplest.

We set the range to 200 mV, connect the positive and negative wires to the sensor terminal and to the metal ring, respectively. Do not confuse ground and signal pin! Now you need to hit it with something metal, but not too hard. The sensor will have to detonate.

You can check the sensor with another device called an oscilloscope. It will allow you to study the signal more qualitatively.

The advantage of using this device is that it does not require removing the sensor from the engine. You just need to connect the device and start the car.

Now you need to tap the sensor lightly. The device will show detonation.

If the sensor detonates, then it is working, and the breakdown must be looked for elsewhere. But if the knock sensor signal is low or there is no signal, then this is a malfunction.

Checking the knock sensor, video:

Symptoms of sensor malfunction

You can determine whether the sensor is broken without a dashboard. But this will require experience and a special approach to your car. You need to know him very well. We list the signs by which you can understand that the device is broken, from here it will be immediately clear what the knock sensor affects:

Replacing the knock sensor

If it requires replacement, then it is necessary to purchase a new device and install it as soon as possible. All car enthusiasts are primarily interested in the price of a new device. It is low and depends on the make of the car and on the country in which the part was manufactured.

Replacement can be done in several ways, the easiest way is to contact a specialist and pay money. On average, all this will cost 2000-3000 rubles.

You can carry out the replacement yourself when the engine has cooled down by disconnecting the negative terminal of the battery. It is necessary to achieve the most convenient access to the sensor so that it can be removed. The fact is that it also depends on the car model.

You can remove it with a 12 mm wrench; to do this you need to unscrew the bolt. Before you pull out the faulty device, unplug it. A new sensor is installed in the same place, and everything is repeated, but only in reverse order.

Thus, knock sensor- This is a simple device, yet very useful for an electronic control system. It is not difficult to determine its malfunction; you can check it yourself, even in rural areas.

It will also be inexpensive to replace the sensor. It doesn’t matter whether this is done by a specialist or independently.

On a VAZ 2110 car, the knock sensor is responsible for damping detonation. This happens by adjusting the ignition timing. Moreover, it is the so-called advance angle that plays an extremely important role in the reliable operation of the power unit.

As a result, it turns out that the device is quite compact in size and performs the most important tasks inside your car. With its help, the engine control system knows that detonation is starting, which allows it to make the appropriate necessary adjustments.

Kinds

For the VAZ 2110, the use of two types of knock sensors is provided.

Broadband. They regularly monitor the noise spectrum and report them to the engine control system. The corresponding signal is processed, the engine adjusts its operation.
Resonant. They perform similar functions to broadband ones, however they only produce signals when the detonation changes.

Small differences between devices do not in any way affect their reliability, service life or efficiency. Therefore, failure of such a regulator is an extremely rare occurrence. But sometimes it happens. Most likely, the cause of the malfunction is the presence electrical circuit break. First of all, it is checked. Most often, after the gap is repaired, the sensor returns to normal operation.

Functionality check

An error with code 34 may appear on the display located on the dashboard of the VAZ 2110. indicates that the knock sensor is faulty and some action should be taken.

But don't rush to buy a new device. It is quite possible that the old sensor is working, and the problem lies somewhere else.
Reset the vehicle's self-diagnosis indicators, drive a few kilometers, and then run the self-diagnosis procedure again.
If the error appears on the display again, you will have to change the meter. In a situation where the error has stopped appearing,
You can use the car for now. Nothing bad happened.
The periodic appearance of error 34 tells you that there may be a break in the connection. Examine the condition of the contacts and wires, strip them, tighten them better. This often solves the problem.

You can determine signs of a malfunction of the knock sensor on a VAZ 2110 by dismantling the device and performing certain manipulations with it.

But first you need to remove the device.

The knock sensor is located on the left of the power unit, where the line of the middle of the cylinder blocks is located. You will see an air filter in close proximity to it. Many people focus on this when searching for a sensor.
De-energize the vehicle by removing the terminal from the battery.
Disconnect the contacts from the sensor and the wiring block. A special lock will allow you to do this if you press it.
Now unscrew the nut securing the device.
All that remains is to remove it from the pin.

Let’s say right away that when reinstalling, you won’t be able to use a regular wrench. Arm yourself with a special torque tool and use a clamping force of no more than 20 Nm.

Taking measurements

Arm yourself with a multimeter, setting it to the minimum values. This universal device can be useful to the car owner at any time. Especially if you prefer to solve most of the problems that arise with your VAZ 2110 on your own;
If you have a single-contact sensor, connect the negative wire from the measuring device (it is traditionally black) to the installation location of the mounting bolt, and the positive wire (red) to the signal contact located in the connector;
If the element is two-contact, then the multimeter is connected according to the rule “plus to plus, minus to minus”;
Further, for both types of sensors the sequence of actions is the same;
To activate the sensor, give it a few light blows. Preferably something hard, like a screwdriver;
If no breakdown is observed in the sensor, then the voltage will begin to jump. Typically, jumps are observed in the range from 40 to 200 mV;
It would be a good idea to check the internal resistance, which normally tends to zero;
If the sensor is OK, check the electronic target;
As practice shows, searching for a cliff is long and problematic. The optimal solution to the problem is to replace the block with wiring;
If the resistance readings are different and there are no voltage surges, you will know for sure that the sensor has failed;
Its replacement is performed in the reverse order of disassembly. There is nothing complicated about it.

The knock sensor is a regular piezoelectric element connected to the ECU controller. The sensor itself is mounted on the cylinder block and must “read” the vibration level. When the engine is running, gasoline can detonate, and the controller, thanks to the sensor, will always “know” about this. In fact, a knock sensor is needed for one reason - to adjust, that is, change the ignition timing. But if the octane number of the fuel was always the same, then there would be no need to adjust anything. If you want to know why, read the text.

The title contains three different concepts, but they are all interconnected. For example, let's look at how it was recommended to configure the distributor on engines with a carburetor:

During operation, it becomes necessary to change the ignition timing. Adjustments, moreover, can be made either up or down - it all depends on the quality of the fuel;
If detonation is observed, it is considered that the ignition is triggered too early. The advance angle needs to be reduced;
If detonation does not occur at all, you can try to increase the advance angle.

The adjustment itself was carried out as follows: unscrew nut 1, and turn the distributor body 2 by 2-3 degrees.

Instructions for a carburetor engine

The instructions usually included the following explanation:

If the octane number of the fuel is lower than that provided by the factory, the advance angle must be reduced. The ignition timing then becomes later, which eliminates detonation.
If the octane number is slightly higher than the calculated one, the advance angle can be increased. The main thing is to make adjustments gradually. As a result, you can get a noticeable increase in power.

Now forget everything that was said before. There is no distributor in the design of injection engines and no adjustment is necessary. Or rather, it should be produced by the ECU controller.

The ignition is controlled by the processor

In the previous chapter we managed to find out that:

By “twisting” the ignition timing “to a minimum”, the occurrence of detonation can be completely eliminated;
By gradually increasing this angle, you can increase power. But after exceeding a certain value, gasoline begins to detonate;
The higher the octane number, the higher the threshold value, and vice versa.

The controller is responsible for setting the advance angle in the injection engine. Moreover, he will reveal the “threshold” itself, that is, the limiting value, empirically. When detonation occurs, it means the threshold has been passed. And in order to identify the detonation itself, you need a “microphone”, that is, a working piezoelectric sensor.

The sensor module is attached to the cylinder block

The sensor housing must also be secured to the engine correctly. Otherwise there will be no point in using it.

Let's summarize. It was fully clarified above why an engine knock sensor is needed. The following describes its structure, as well as the consequences of failure.

The sensor is broken - so what?

If the engine has just started, the advance angle will be set to a minimum. Then the value gradually increases, but only until detonation occurs. And if the sensor was faulty, the controller would behave like this:

The value will increase to the maximum, then a certain number of cycles will be maintained;
A stable signal does not come from the sensor - a conclusion is drawn that it is faulty;
The advance angle is immediately reduced to minimum values. The Check lamp comes on.

At first glance, everything looks correct - the controller has “calculated” the fact of a breakdown. But the fact is that in step 1 the motor was operated in critical mode.

The more starts there are with a faulty sensor, the faster you can “kill” the engine. Everything is obvious here, isn't it?

You can drive as long as you like with a faulty knock sensor. Critical, as already mentioned, will be the number of launches.

Typical faults

The reader has already been able to understand how the knock sensor affects engine operation. The breakdown of this sensor does not lead to anything good - the power is reduced, and each start is perceived painfully by the engine. It is interesting that the knock sensor also reacts to suspension shocks, without distinguishing them from fuel detonation. And to eliminate “false alarms”, a rough road sensor (RSD) is installed.

DND is rigidly attached to the body

A knock sensor failure is indicated by the lamp turning on.Check.If you have an on-board computer, try to decipher the code:

P0324 – errors in the detonation control system;
P0325 – open or shorted sensor contacts;
P0326 – the sensor produces an unreliable signal;
P0327 – signal level too low;
P0328 – signal level too high.

As you can see, malfunctions include not only the absence of a signal, but also its amplitude being too high. The controller needs the signals from the sensors to be within certain limits. Otherwise, apparently, the system will not analyze the shape of these signals, which is tantamount to the complete absence of a sensor.

Device and method for checking DD

How the engine knock sensor works has not yet been considered. That is, you need to understand what the principle of its operation is based on. And it is based, as many people know, on the phenomenon of the piezoelectric effect.

Let's say two wires are connected to the edges of a piezoelectric crystal, and the crystal itself experiences deformation. Then electrical voltage appears on the wires. Its value increases with increasing amplitude of influences, which makes it possible to use a piezoelectric sensor as an acceleration meter.

Conclusion: The knock sensor measures acceleration and nothing else.

How to check if the DD sensor is working

Actually, they check the sensor like this: connect the leads to a multimeter, tap the body with a screwdriver. The instrument scale should display at least some numbers (not “0”).

And now - seriously:

In professional workshops, the sensor is connected not to a voltmeter, but to an oscilloscope;
When using a multimeter, use the maximum sensitivity threshold;
It makes sense to measure the resistance of the sensor - it cannot be less than 100 kOhm.

Before performing any installation work, disconnect the negative terminal of the battery. You can connect it when the installation is complete.

Varieties and compatibility

It would seem that the design of all knock sensors looks the same, and therefore they should all be compatible. However, in reality everything will be more complicated. The number of pins on the sensor is always two. But the shape of the connector may differ. And most importantly, even the internal electrical resistance is different:

Sensors designed for VAZ engines have almost infinite resistance (cannot be measured);
Typical DD resistance for Subaru and Nissan is 500 - 560 kOhm;
Hyundai DD resistance is 5 megaohms.

Sensor modules may also differ in shape:

Three different DD sensors

If we talk about Chinese cars, you can find out this:

For all Lifan engines, the DD with the number LF479Q1-3612200A or LF479Q3-3612200B is suitable;
The part with the designation LBA3612400B1 is an original Lifan DD;
DD “0261231176” (engine ZMZ-405/409 EURO-3) will be fully compatible with the Lifan sensor;
Electrically, but not by connector, the sensor from ZMZ-406 (EURO-3) is compatible with Lifan.

Checking DD with a screwdriver, video example

Many car enthusiasts are familiar with the situation when, after stopping the engine, it continues to detonate, that is, for some time it rotates chaotically, “twitches,” until it comes to a complete stop. If you fill a car with low-quality gasoline while driving, especially at increased load, the car may also exhibit uneven engine rotation. There is an effect of engine detonation.

Detonation is a very dangerous phenomenon because it causes repeated overloads on engine components, especially pistons, valves, crankshaft, camshaft, and timing belt. Photo: westerncanadacorsa.com

Since the beginning of the 80s, knock sensors began to be installed in engine control systems, which generate a certain signal when a detonation effect occurs, communicate it to the engine control unit, which in turn adjusts the ignition timing, preventing the detonation effect.

Detonation effect

The effect of engine detonation is the spontaneous chaotic ignition of a combustible mixture, which occurs without the participation of the engine ignition system.

For example, if you fill a car with low-quality gasoline with a lower octane number than stated at the gas station and required in the car’s operating instructions, when a certain degree of compression is reached in the working area, the mixture may ignite even before the ignition spark is ignited.

Depending on the compression in each of the cylinders (it is usually different, especially for used engines), the moment of ignition of different cylinders will be different, the engine begins to “sausage”, that is, to detonate. At the same time, its torque and power are significantly reduced.

If you mentally look inside the cylinders, you will see the following picture. Photo: nulonbornthisway.com.au

Serious overloads can be caused by:

damage to the valve group;
increased piston wear;
reduction in timing belt life;
more serious problems up to a block crack.

In addition to low-quality fuel, the following factors can cause detonation:

setting the wrong ignition angle when replacing the timing belt;
wear of tension and guide rollers, timing belt;
engine design parameters, increased compression;
type and wear of spark plugs;
vehicle operating conditions, operating coolant temperature.

Principle of operation

Most modern sensors installed on cars use the piezoelectric effect. It lies in the fact that some materials, when exposed to mechanical forces, form a potential difference (electrical voltage).

In everyday life, most smokers are familiar with a piezo lighter. In it, the striker knocks on the piezoelectric element, resulting in a fairly powerful spark. The signal magnitude in the knock sensor is much smaller, but the principle is the same.

There are two main versions: resonant and broadband.

Some VAZ car models use broadband sensors. Photo: les-sfu.ru

The sensors are installed in that part of the engine that is located directly next to the ignition zone, this is the cylinder block. It is especially important that the fastening has maximum rigidity. Some car enthusiasts, not realizing the importance of the knock sensor, attach it incorrectly after an engine overhaul, significantly worsening the parameters of the internal combustion engine.

The advantage of wideband sensors is that they work effectively when driving at high revs and speeds. At the moment of switching to low speeds and when stopping the engine, their sensitivity does not decrease.
Resonant sensors have greater sensitivity compared to broadband ones, but in a small range of engine speeds. The Toyota manufacturer chose this type of sensor.

These sensors have maximum efficiency at low speeds due to the resonance effect in the spring mounting system of the piezo element. That is, these sensors use two physical effects simultaneously: mechanical resonance and the piezoelectric effect. To increase the quality factor of the resonant curve, a shunt resistor is usually built into the sensor.

Resonant sensors have another advantage over broadband sensors: they are not so sensitive to vibration when the car is driving on a road with poor coverage.

Resonance sensors are usually mounted by screwing them into standard engine locations. The sensors have a built-in threaded area. Some car enthusiasts confuse them with oil pressure sensors.

In some engines, two or more knock sensors are installed, thereby forming a more complete picture of the nature of ignition in the cylinders. Photo: midasauto.ru

Symptoms of a problem

A faulty knock sensor can work for a long time and not show itself in any way if the engine does not detonate, is always filled with good gasoline, and is serviced on time. The main symptom of a faulty knock sensor is the manifestation of engine knocking.

A secondary sign of malfunction is the appearance of cracks and chips on the body, oxidation of contact zones, discoloration of the structure, and the manifestation of corrosion effects. In all of the above cases, it is necessary to diagnose the serviceability of the knock sensor.

A mandatory check of the sensor must be carried out if the car is involved in an accident with damage to the hood area. Since the sensor is rigidly attached to a massive motor, due to high overload at the moment of even a small impact, a critical displacement of the sensitive piezoelectric element can occur. Sensor parameters may change significantly. Such a change cannot always be registered by computer diagnostics. Many dealership auto centers replace knock sensors after serious accidents even without monitoring their performance.

Once again, find out how the knock sensor works and how you can check it - find out from the video:

Sensor check

The first stage of checking the knock sensor is computer diagnostics in static (reading errors) and dynamic (studying characteristics) modes. If the diagnostics showed that there is a knock sensor error, the first thing you can do is connect a known-good sensor, reset the errors and re-diagnosis.

If the error message appears again, check the electrical wiring up to the engine control unit.

Diagnostics do not always respond to a malfunction of the knock sensor. You can perform the “old-fashioned” diagnosis. To do this, start the engine, warm it up to operating temperature, put the car on the parking brake without turning off the engine, get out of the car, take a small hammer, and begin to methodically (but not forcefully) tap on the knock sensor mount. At this point, the engine should (but does not have to) change speed slightly. But if it changes, then it’s definitely working.

You can check the sensor using a measuring device. To do this, take a simple multimeter. Then it is switched to voltage measurement mode at the maximum sensitivity limit (200 or 2000 millivolts). Next, connect its probes to the terminals, as shown in the figure:

Since two hands are already occupied, you can ask your neighbor in the garage to knock with a hard object on the body near the mount. Before knocking, the device readings should be approximately zero (especially if you do not touch the body and probes with your hands). At the moment of knocking, the multimeter readings should increase significantly, sometimes up to 1 Volt or more. More visual characteristics can be obtained using an oscilloscope, but this is hardly necessary. The knock sensor, in principle, can be used as a microphone. There are piezoelectric microphones based on the same principle. Some highly experienced mechanics listen to the engine with their ears. Almost the same function is performed by the knock sensor.

Replacing the sensor

If a sensor failure is suspected, there is noticeable damage to its structure, or severe damage to the engine during an accident, the sensor must be replaced. Theoretically, the knock sensor has a service life that significantly exceeds the service life of the engine, so “just in case” it should not be changed.

It is better to replace the sensor with a new one. Sometimes, based on the appearance of a used vehicle that has undergone pre-sale preparation, the sensor cannot determine its performance. The exception is cases when it is impossible to find a new sensor for a given model or it has an inadequate cost. In this case, you can look at sensors for other models of sensors for engines of the same manufacturer. As a rule, designers install almost identical sensors on engine lines. The main thing is that it clearly fits the installation parameters.

However, the VAZ manufacturer strongly does not recommend changing sensor types for different models. If during diagnostics of VAZ engines error 0325 (open circuit) was detected, the sensor may be working properly; you should check the electrical circuit for an open circuit. Error 0328 (increased signal level) can occur due to interference from high-voltage wires or increased mechanical noise from the engine. But errors 0326 and 0327 (low signal level) are most likely evidence of a sensor malfunction.

On a VAZ 2110, to replace the sensor, remove the connector, as shown in the figure. Photo: autoeo.ru

Then, using a plumbing tool, unscrew the resonant knock sensor and thoroughly clean the installation location. The new sensor is installed using a torque wrench, setting the tightening torque to about 15 - 20 Nm. After this, connect the connector, turn on the ignition, use computer diagnostics to reset previous errors, start the engine, and perform a test drive. Then computer diagnostics are performed again. If it shows no errors, the repair is considered successful.

Video instructions for replacing the DD can be found here:

Advice for car enthusiasts

To be sure that the knock sensor is working properly, keep an eye on:

state of sensor mounting;
absence of foreign liquids, oils, antifreeze from entering the sensor housing and connector;
the nature of the engine movement at the moment of shutdown.