Car Sensor List, How car Sensors work, Check engine sensors

Car Sensor: Checking engine sensors are largely similar to each other, despite fact that these devices measure various physical quantities and values. To test most of them, an electronic multimeter used, capable of measuring value of electrical resistance and voltage.

However, most sensors can checked by other methods, depending on the principle of their operation. Before checking sensors, it is necessary to dismantle them from their seat, because in most cases verification directly on the spot is impossible.

Consider purpose and methods of checking main sensors under hood of any modern car. Since, if at least one of them fails, operation of the entire engine will disrupted.

Mass airflow sensor

As the name implies, abbreviated as DFID, measures volumetric amount of air intake by engine. Unit of measure, in this case, is kilograms per hour. For most machines, this sensor mounted on the air filter housing or on the intake manifold. Its device is simple, so it crashes quite rarely. However, in some cases, it can capture and issue incorrect information.

For example, when readings overestimated by 10… 20%, problems arise in the operation of the engine, in particular, they can “float” at idle speed, motor “chokes” and does not start well. If the values ​​of the readings from sensor are lower than they actually are, then the dynamic characteristics of the machine fall (it does not accelerate, it goes slightly uphill), and fuel consumption also increases.

Correct operation of the mass air flow sensor is very dependent on the state of the air filter. So, if the latter very clogged, then there a risk of trash elements – grains of sand, dirt, moisture and so on, which is very harmful to it, and leads to the fact that sensor gives incorrect information. This can also happen if a zero resistance filter installed on the machine (or there is simply no filter).

An interesting feature of mass air flow sensor that machines equipped with it cannot tuned, increasing power of motor. In particular, this applies to VAZ engines, which some motorists “swing” to a power value of 150 … 160 horsepower. In this case, sensor will obviously not work correctly, since it simply not designed for such an amount of air flowing into engine.

For standard VAZ engines, mass air flow sensor at idle should record passage of about 8 … 10 kilograms of air per hour. With an increase in speed to a value of 3000 rpm, corresponding value increases to 28 … 32 kg / h. For engines similar in volume to VAZ engines, these values ​​will be close or similar.

Checking mass air flow sensor consists in measuring DC voltage it emits using an electronic multimeter.

Throttle position sensor

Sensor designed to fix position of the throttle at a particular point in time. Corresponding position changes depending on whether accelerator pedal depressed and how much. Typically, throttle position sensor is mounted directly on the throttle and/or on the same axis as throttle.

It is noted that if an original high-quality sensor installed on the machine, then there will most likely be no problems in its operation. However, there are many fake low-quality sensors on sale (for example, Chinese-made), which, firstly, do not last long (about a month), and secondly, provide incorrect information, which leads to engine operation in conditions that are not optimal for it.

For example, with a partial output of throttle position sensor, problems arise in the reaction of the machine to the actions of driver with respect to the gas pedal. For example, dips appear when you press it, spontaneous increase in speed, their “swimming”. Also, in case of a malfunction of throttle position, jerks and dips during engine operation under load are possible. In a word, accelerator pedal “begins to live its own life”.

There cases when TPSs failed due to the fact that they were damaged in a car wash with a powerful water jet. Up to the point that they can simply knocked down from their seat. Therefore, you need to carefully monitor this when performing a car wash on your own or in a specialized institution. In general, the throttle position sensor is a fairly reliable device. However, when it fails, it cannot repaired, so it should only replaced completely.

You can check throttle sensor with a multimeter that can measure DC voltage in the range up to 5 Volts.

Coolant temperature sensor

It has other names – temperature sensor, coolant sensor. As name implies, its task is to fix temperature of antifreeze or antifreeze, and transmit this information to the electronic engine control unit (ECU). Based on information received, control unit corrects enrichment of the air-fuel mass entering engine, respectively, colder the engine – the more rich this mixture will be. Coolant temperature sensor is most often located on the exhaust pipe of the cylinder head (although there may be other options, it depends on the specific car model).

In fact, this sensor is a thermistor – that is, a resistor that changes its internal electrical resistance depending on the temperature of its control element. Lower temperature, higher resistance, and vice versa, higher temperature, lower resistance. However, sensor supplies computer with a voltage value, not resistance. This implemented by sensor control system when 5-volt signal supplied to it through resistor with constant resistance, which located inside control controller. Therefore, together with resistance, output voltage also changes. So, if the antifreeze temperature is low, the output voltage will be large, and as it warms up, voltage will decrease.

Signs of sensor failure:

Spontaneous inclusion of cooling fan with a cold engine; not turning on the cooling fan when engine is hot (at extreme temperatures, when it should turn on); problems starting engine “hot”; increased fuel consumption.

In fairness, it is worth noting that sensor device is quite simple, and there’s simply nothing to break there. However, in some cases (for example, due to mechanical damage or from old age), electrical contact inside sensor may damaged. Second possible cause of failure is a break in the wiring from the sensor to the computer or damage to its insulation. As in case with other sensors, this unit cannot repaired, and it only needs to replaced with a new one.

Checkingcoolant temperature sensor can done either directly at its seat in engine or by dismantling it first.

Knock sensor

Knock sensor (abbreviated DD) detects appearance in engine directly of detonation knocks. Typically, the knock sensor mounted directly on the engine block, most often between second and third cylinders. Currently, there are two types of such sensors – resonant and broadband.

First of them (resonant) considered obsolete, and they can only found in engines of old designs. Tesonance sensor designed for a specific sound frequency, which corresponds to microexplosions in the motor. A broadband sensor detects sound waves in the range from 6 Hz to 15 kHz.

Relevant information transmitted to the electronic control unit, and already control unit decides whether detonation is taking place or not. And if it does exist, then computer automatically shifts the ignition angle to avoid a repetition of it.

Signs of failure of knock sensor are following factors:

• loss of dynamic characteristics of machine (it does not accelerate, pulls poorly uphill);
• idle speed “float”, they can also be unstable in operating mode;
• increase fuel consumption.
• Knock sensor can checked by two methods – by measuring value of the output resistance, voltage, or using oscilloscope to watch mode of its operation in dynamics.

Oxygen sensor

Another name for sensor a lambda probe. Main task of unit is to fix amount of oxygen in the exhaust gases. As a rule, it installed near catalyst or on the exhaust pipe of the muffler. In some car models, the design provides for use of two oxygen sensors – one before catalyst, and second after. The relevant information traditionally transmitted to the electronic control unit, and it already makes a decision on fuel supply to engine, adjusting composition of the air-fuel mixture (poor/rich). If oxygen is detected in the exhaust gas, then mixture is poor, if not detected, it rich.

Oxygen sensor itself is quite reliable, and rarely fails. However, if this happens, then the emission of harmful substances along with exhaust gases into atmosphere increases. Externally, failure of lambda probe can determined by increased fuel consumption. A conditional disadvantage of sensor its relatively high price compared to other car sensors.

Oxygen sensor checked both by visual method and by a tester. Method of voltage measurement and signal supply will depend on how many contact specific lambda taken.

Crankshaft position sensor

Its abbreviated name is DPKV. This is one of main sensors of internal combustion engine, and all its work depends on it. Task is to generate an electrical signal about a change in the angular position of a special gear disk fixed to crankshaft. Based on this information, electronic engine control unit decides at what time in which cylinder to supply fuel and light a candle. Typically, crankshaft position sensor mounted on cover of the oil pump. Structurally, device is very similar to a conventional magnet with a thin wire.

If DPKV sensor fails, two situations may occur. First is that the engine completely stops working, because synchronization of fuel supply, sparks and so on lost. This happens most often. However, in some cases,electronic control unit puts engine in emergency mode, in which engine speed limited to 3000… 5000 rpm. At same time, Check Engine warning light activated on the dashboard.

Checking the crankshaft position sensor performed by three methods: resistance, inductance and an oscilloscope measured.

Speed ​​sensor

It is located on the gearbox and fixes shaft rotation speed, transmitting relevant information to the electronic control unit. And computer already calculates speed based on the information received. In cars with a manual transmission, relevant information transmitted to speedometer located on dashboard. In machines equipped with automatic transmission, on the basis of information including from it (but not only).

But a decision also made to shift gears to increase or decrease. Also, based on the information from speed sensor, car’s mileage calculated, that is, odometer is running.

Sensor provides voltage pulses to electronic control unit in range from 1 to 5 Volts with a frequency proportional to the speed of rotation of the wheels. By their frequency, device calculates speed of the machine, and by number of pulses – distance traveled.

Sensor itself is a fairly reliable device, however, in some cases, plastic gear wears out, its contacts may oxidize, which leads to ECU problems. In particular, control unit cannot understand whether car is standing or driving, and at what speed. Accordingly, this leads to problems in operation of speedometer, as well as gear changes in automatic transmission.

Also, when sensor fails (contact oxidation), lower idle speeds noted, with sharp braking, the engine speed “sags” strongly, dynamic characteristics of the machine decrease (it slightly accelerates, does not pull). On some vehicles (for example, on some Chevrolet models), electronic control unit in emergency mode shuts off engine, and movement becomes impossible.

Checking speed sensor requires using one of the three available methods.

Camshaft position sensor

Similarly, DPCV, camshaft position sensor (abbreviated DPRV) reads information about angle of its position and transfers corresponding information to computer. Based on the information received, the control unit decides to open fuel nozzles at a certain point in time.

On the old injection engines (until about 2005), camshaft position sensor not installed. Because of this, fuel injection into the intake manifold on such engines carried out in pairwise-parallel mode, in which two nozzles open simultaneously, which characterized by excessive fuel consumption.

On the engines on which DPRV installed, so-called phased fuel injection performed. That only one injector nozzle opens, where fuel should supplied at the moment. As for location of the sensor, on eight-valve engines it mounted at end of the cylinder head. On sixteen-valve power units, this sensor is also usually located on the cylinder head, near first cylinder.

When camshaft position sensor fails,electronic control unit puts engine into emergency mode, in which the nozzles operate in pair-parallel mode, opening simultaneously. This leads to an excessive consumption of fuel by 10… 15%, in some cases engine “troit”. Usually, an error signal generated in computer, and Check Engine warning light activated on the dashboard. Therefore, additional diagnostics must performed using electronic error scanner.

Checking LPR sensor can done using a multimeter and/or oscilloscope.

Anti-lock sensor

As name implies, this node is key to the anti-lock system (abbreviated as ABS). On machines equipped with this system, there is one such sensor on each wheel. Their task is to fix speed of rotation of the wheel at a particular point in time. Location method for machines may be different, however, in any case, the sensor will be located in close proximity to the rim, in vicinity of the hub. Usually, signal wires go to it, by which it is possible to determine exact location of the sensors on the front and far wheels.

As a rule, sensors themselves quite reliable, and rarely fail, except due to mechanical damage associated with fact that they installed in close proximity to the wheel and road. More often, wiring going to / from them damaged. It may fray or insulation will damaged on the wires. If electronic control unit “sees” that incorrect information is coming from sensor / sensors, it activates Check Engine warning light on the dashboard, and ABS system simply turns off in emergency mode. Naturally, this leads to a decrease in driving safety.

ABS sensor checked in various ways – by measuring resistance, voltage, or using an oscilloscope (most advanced method). On newer machines, Hall effect sensors installed as ABS sensors.

Hall Sensor

Sensors whose operation based on Hall effect (why they are called so) are used in electronic ignition systems. Their application provides two main advantages – absence of a contact group (a problem node that can sometimes burn), as well as providing a higher voltage on the spark plug (30 kV instead of 15 kV). However, similar sensors are also used in other systems of modern cars – brake, anti-lock, in the operation of tachometer. However, principle of verification is almost same for them and consists of measuring the resistance and/or voltage on the sensor with an electronic multimeter.

If Hall sensor located in the electronic ignition system fails, following external signs of this failure occur:

problems with starting engine up to the complete inability to start it;
problems in engine idling (interruptions, unstable engine speeds appear); twitching of the car when driving in a mode when engine has gained high speed; engine stalls while machine is moving.

Hall sensor is a fairly simple and reliable device, but in some cases, it can “lie”, that is, produce incorrect data. If, as a result of check, it turns out that sensor has completely or partially failed, then it unlikely to repaired (and there is no point in this), therefore, it necessary to replace it. Sensor in the ignition system of the carburetor car is located in distributor.

Checking Hall sensor in ignition system can done in one of four ways.

Oil pressure sensor

There are two types of oil pressure sensors (or DDM for short) – mechanical (considered obsolete and installed, respectively, on old cars) and electronic (modern, installed on most modern cars). Regardless of its type of DDM, position of the oil pressure sensor is usually located in the oil filter area in engine compartment.

Oil pressure sensors are fairly reliable devices (although a mechanical one breaks down more often, because its design has moving electrical contacts that fail over time), but there are malfunctions in their wiring (wire breakage, insulation damage). Signs of failure of sensor will be problems with indication of pressure and / or oil level in engine.

Please note that if problems arise in operation of the oil pressure sensor, diagnostics should performed as quickly as possible, since a low level of lubricating fluid in crankcase a critical indicator, and it must always kept at a normal value constantly!

Checking oil pressure sensor is only possible when dismantling from seat. To check motorist will need an electronic multimeter (it can replaced by a control lamp) and an air compressor.

Fuel pressure sensor

Fuel pressure sensor designed directly so that ECU, in fact, receives information about value of this pressure. These devices install both gasoline engines equipped with injectors and modern diesel engines with the Common Rail fuel system.

These sensors installed in fuel rail of the engine. In gasoline and diesel engines, task of the fuel pressure sensor is the same, and consists in providing a pressure value in a certain framework necessary for the normal functioning of the motor, ensuring its rated power, and normalizing noise during its operation. Some systems provide for installation of two sensors – in high and low pressure systems.

Structurally, sensor is a sensor element consisting of a metal membrane and strain gauges. The thicker membrane, more pressure sensor designed for. Task of strain gages is to convert mechanical bending of membrane into an electrical signal. The output voltage value is about 0 … 80 mV.

If pressure value outside specified limits (these values ​​are stored in the memory of the electronic control unit), control valve in fuel rail is activated in system and pressure adjusted accordingly. In event of a sensor failure, computer activates Check Engine warning light on the dashboard and starts using standard (unregulated) fuel consumption values. This leads to the non-optimal operation of the engine, which reflected in excessive consumption of fuel and loss of engine power (dynamic characteristics of machine).

Information about checking fuel pressure regulator you can read separately.

Absolute pressure sensor

In classic version, absolute air pressure sensor (DBP) made of four resistors with a variable resistance value, and which connected by an electronic bridge. They are glued to a diaphragm, which either compressed or stretched depending on what pressure of the incoming air currently at the intake manifold.

Task of DBP is to record change in pressure at inlet pipe depending on the change in load and engine speed, converting this information into an output electrical signal. This signal is traditionally fed to the electronic control unit, and based on this information, computer changes duration of fuel supply to the combustion chambers, as well as the ignition timing.

As a rule, air pressure sensor is located on the intake air tract (depending on the design of a particular car). When it fails, problems begin in engine – idle speed “floats”, car loses dynamic characteristics, fuel consumption increases. If sensor is damaged, it must be replaced with a new one.

Phase sensor

Operation of phase sensor is based on the aforementioned Hall effect. Its task is to fix so-called top dead center compression of piston of first cylinder. Televant information transmitted to the computer, and on its basis, phased fuel injection into the remaining cylinders performed in accordance with operating order of the engine cylinders. Typically, phase sensor installed at the rear of cylinder head.

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When phase sensor fails, an out-of-phase injection of fuel into cylinders occurs, that is, engine enters the unphased fuel injection mode. The electronic control unit activates the Check Engine warning light on the dashboard. In this case, engine starts to work unstable, up to a complete stop, a decrease in the dynamics of car in different driving modes, engine “troit”. In some cases, on the contrary, increased fuel consumption noted. Replacing sensor straightforward. Usually you just need to use a wrench.

You can see partial information on how phase sensor checked in a separate topic.

Intake air temperature sensor

Sensor abbreviated as DTVV or in English abbreviation IAT. It is necessary so that air-fuel mixture has an optimal composition for operation of engine. As a rule, intake air temperature sensor is installed on the air filter housing or behind it, that is, in places where the air directly drawn into the engine. In some cases, it may be part of a mass airflow sensor.

Failure of indicated element threatens unstable engine operation, floating idle speed (they will be either too high or too low), loss of dynamics, and power of car. Also, with a faulty unit, there will be problems with starting engine, as well as a significant excessive consumption of fuel, especially in severe frosts.

A sensor malfunction can caused due to damage to its electrical contacts, failure of its signal wiring, low voltage in electric vehicle network, a short circuit inside sensor, and contact contamination. In fairness, it should noted that this sensor, unlike many others, can be restored to its functionality, that not to replace. Sometimes elementary cleaning also helps (you need to do it carefully).

Checking operation of intake air temperature sensor carried out using an electronic multimeter.

Sensor Check

In most cases, verification process is simple and does not take much time. Before performing the check, it recommended to scan memory of electronic control unit for errors using a special scanner (for example, popular ELM 327 device or its equivalent). This will simplify verification of both a specific sensor and a malfunction of the car as a whole.

Sometimes situations arise when the location of a sensor is unknown. In this case, it is better to seek help from manual. Also, on specialized sites there is information about position of sensors on specific car models.

Conclusion

Before checking this or that sensor, you need to make sure that signs of breakage indicate precisely failure of a particular sensor. If you have doubts about this, it is best to seek help from a car service. Direct verification in most cases carried out using an electronic multimeter capable of measuring electrical resistance and constant voltage in the range up to 12 volts.

Therefore, purchase such a device if you do not already have it. It not necessary to take expensive samples, an ample device from the middle price category (very cheap should not bought either, since it may show incorrect data). Well, for the dismantling of sensors, you must have at hand the usual locksmith tools – wrenches, screwdrivers, and so on.