The operation of the crankshaft position sensor (abbreviated as DPKV) is very important. Thanks to its indicators, the electronic engine control unit knows exactly what position the shaft is in, and therefore the pistons, and can clearly give commands to the ignition and fuel injection systems. It would not be an exaggeration to say that the DPKV is the main electronic sensor of a car, without which the operation of a modern engine is absolutely impossible. This is one of the few elements of the car, the failure of which leads to a complete stop of the power unit.
CRANKSHAFT SENSOR FUNCTIONS
The main function of the DPKV is the constant measurement of the position of the crankshaft.
Using this data, the engine ECU determines the crankshaft speed and its angular velocity, which makes it possible to solve the following tasks:
fixing the moment the pistons are at TDC (top dead center);
determination of the moment of injection and the optimal duration of the injectors;
determining the moment of ignition in the cylinders;
change in valve timing;
control of the operation of the adsorber valve (fuel vapor recovery system);
correction and control of other systems.
The crankshaft position sensor is used in both gasoline injection engines and diesel engines. The information received from it makes it possible to synchronize the operation of all nodes, one way or another connected with the rotation of the engine shafts - crankshaft and distribution. In modern engines, DPKV works in tandem with DPRV - a camshaft position sensor, sometimes they are even interchangeable.
VARIETIES AND DEVICE DPKV
What is dpkv
In cars with carburetor engines and a contact ignition system, the crankshaft sensor was located in the ignition distributor (distributor), which had a rigid connection with the shafts - crankshaft or distribution. With the advent of the contactless system, sensors similar to those installed on modern cars began to be used.
The location of the sensor depends on the type of engine and may vary even among modifications of the same car model.
Most often, DPKV are installed:
opposite the toothed drive disk (also called counting ring) mounted on the crankshaft pulley;
opposite the master ring of the flywheel, installed in tandem with the main crown.
The second method relates more to obsolete engine designs. In some cases (for example, on Subaru engines), two crankshaft sensors may be present on the engine, located in both places described - one determines the TDC of the pistons, and the other serves to determine the crankshaft speed.
There are three main types of crankshaft position sensors:
Hall sensor based. This type works with a magnet located on a disc or flywheel. At the moment the magnet passes by the sensor, a current is excited in the DPKV, and the information (impulse) is transmitted to the ECU. The sensor is complex in design, requires a separate power supply, but provides maximum accuracy.
Optic. It consists of an LED and a photodiode (light source and receiver), between which there are teeth or holes in the driving disk. The flickering light as the disk rotates generates pulses transmitted to the control unit. Due to the difficulties (contamination, the possibility of smoke), little is used.
Inductive (magnetic) DPKV. Works on the principle of electromagnetic induction. At the moment of passing by the sensor of the tooth of the synchronization disc, voltage is induced; in the absence of a tooth, it is absent. The driving disk in this case is deliberately devoid of teeth (for example, two out of 60). The simplest and most commonly used sensor.
The crankshaft position sensor is fastened with one or two bolts, while the gap between the sensor and the drive disk must have a strict value - if it increases or decreases, the readings will not be correct.
SYMPTOMS OF A FAULTY CRANKSHAFT SENSOR
There are various symptoms that can indicate a malfunctioning DPKV, depending on the severity of the problem. Typical symptoms are:
reduction in engine power - especially under load;
unstable speed in all modes;
increase in fuel consumption;
dips when pressing the accelerator pedal;
detonation at high speeds;
engine vibration, often accompanied by clanging sounds;
misfiring and tripling;
sudden stoppage of work;
inability to start the engine;
the appearance of the Check Engine indication.
Since many of these symptoms may also indicate problems in other vehicle systems, diagnostics using a scanner will be most revealing. In the OBD II protocol, a sign of a DPKV malfunction will be error P0336 (“signal out of range”, “missing one tooth”, etc.).
It is worth noting that often the “check” does not light up immediately, as soon as problems with DPKV appear. The control unit detects the deviation of indicators from the norm (omissions or, conversely, excessive pulses) only if they are repeated over several tens of cycles of rotation of the master disk - on average, about 50 revolutions, and most often not immediately, but after
Vuh-three emergency engine starts.
CAUSES OF FAULTS OF THE DPKV
In general, the crankshaft position sensor is a fairly reliable device that rarely fails. Breakdowns are associated not so much with the sensor itself, but with its wiring and related components.
Among the main reasons:
damage to the sensor winding due to vibration, oxidation or due to poor quality of the product (too thin wire, insulation, etc.);
damage to the LED or photodiode, their contamination (for optical sensors);
violation of the distance between the setting disk and the DPKV sensor;
wear or damage to the driving disk (gear wheel);
hit on the toothed part of the disk of foreign objects;
damage to the sensor connector or corrosion of the terminals;
breakage or short circuit of the sensor wires;
ECU problems.
In some (rare) cases, with misfires in the cylinders, the control unit may erroneously diagnose a DPKV error.
HOW TO TEST THE CRANKSHAFT POSITION SENSOR
If you suspect that the sensor is working, you need to start by checking the integrity of its circuit. Due to the location of the DPKV, its wires are usually long, and if they are not properly or securely fastened, they are prone to breakage or contact with hot parts of the engine (catalyst, exhaust system), which leads to melting and shorting.
The next step, if the wires are normal, you can check the resistance of the winding (applies to inductive DPKV). For a good sensor, it ranges between 550 and 750 ohms. To do this, you need a multimeter or ohmmeter. It is not necessary to dismantle the sensor, it is enough to remove the connector.
A defective sensor is almost beyond repair, so if it does not meet the required parameters, it must be replaced. It is recommended to always have a DPKV in stock to avoid immobilizing the car in the event of a breakdown.
If the failure is repaired, or there is a possibility of an erroneous occurrence of a fault code, it must be erased from the computer's memory. It is advisable to use diagnostic equipment (scanner) for this, and not to throw off the battery terminal. In addition to the fact that errors are not always removed in this way, it is also possible to provoke the appearance of a new one - “interruption of the on-board network voltage”.
The crankshaft position sensor is a serious electronic assembly, the malfunction of which, as we already know, can lead to serious engine problems and the inability to continue driving. Therefore, if you are not confident in your own abilities and competence, seek help from professionals - for example, at any of the service stations of the Wilgood smart car service network, whose competent and qualified specialists will eliminate any malfunctions of your