How to check tire pressure sensors

Check tire pressure sensors it is possible not only at the service with the help of special devices (TPMS diagnostic tool), without dismantling them from the wheel, but also independently at home or in the garage, only if it is removed from the disk. The check is performed programmatically (using special electronic devices) or mechanically.

Tire pressure sensor device

The tire pressure monitoring system (in English - TPMS - Tire Pressure Monitoring System) consists of two basic components. The first are precisely the pressure sensors located on the wheels. From them, a radio signal is transmitted to a receiving device located in the passenger compartment. The receiving device, using the available software, displays the pressure on the screen and its decrease or discrepancy with the set one will light the tire pressure monitoring lamp.

There are two types of sensors - mechanical and electronic. The first are installed instead of the spool on the wheel. They are cheaper, but not as reliable and quickly fail, so they are rarely used. But electronic ones are built into the wheel, much more reliable. Because of their internal location, they are better protected and accurate. About them and will be discussed further. The electronic tire pressure sensor structurally consists of the following elements:

• pressure measuring element (pressure gauge) located inside the wheel (tire);
• microchip, the task of which is to convert the analog signal from the pressure gauge into electronic;
• sensor power element (battery);
• an accelerometer, whose task is to measure the difference between real and gravitational acceleration (this is necessary to correct pressure readings depending on the angular velocity of a rotating wheel);
• antenna (in most sensors, the metal cap of the nipple acts as an antenna).

What battery is in the TPMS sensor

The sensors have a battery that can work offline for a long time. Most often these are lithium cells with a voltage of 3 volts. CR2450 elements are installed in the sensors that are inside the wheel, and CR2032 or CR1632 are installed in the sensors mounted on the spool. They are cheap and reliable. The average battery life is 5…7 years.

What is the signal frequency of the tire pressure sensors

Tire pressure sensors designed for installation on European и asian vehicles operate on a radio frequency equal to 433 MHz and 434 MHz, and sensors designed for of american machines - on 315 MHz, this is established by the relevant standards. However, each sensor has its own unique code. Therefore, the sensors of one car cannot transmit a signal to another car. In addition, the receiving device "sees" from which sensor, that is, from which particular wheel the signal comes.

The transmission interval also depends on the specific system. usually, this interval varies depending on how fast the car is traveling and how much pressure it has in each wheel. Usually the longest interval when driving slowly will be about 60 seconds, and as the speed increases, it can reach 3 ... 5 seconds.

The principle of operation of the tire pressure sensor

Tire pressure monitoring systems operate on the basis of direct and indirect indications. Sensors measure certain parameters. So, to indirect signs of a pressure drop in the wheel is an increase in the angular velocity of rotation of a flat tire. In fact, when the pressure in it drops, it decreases in diameter, so it spins a little faster than another wheel on the same axle. In this case, the speed is usually fixed by the sensors of the ABS system. In this case, the ABS and tire pressure monitoring systems are often combined.

Another indirect sign of a flat tire is an increase in the temperature of its air and rubber. This is due to the increase in the contact patch of the wheel with the road. The temperature is recorded by temperature sensors. Most modern sensors simultaneously measure both the pressure in the wheel and the temperature of the air in it. Pressure sensors have a wide temperature operating range. On average, it ranges from -40 to +125 degrees Celsius.

Well, direct control systems are a nominal measurement of air pressure in the wheels. Typically, such sensors are based on the operation of built-in piezoelectric elements, that is, in fact, electronic pressure gauges.

The initialization of the sensors depends on the parameter they are measuring. Pressure sensors are usually prescribed using additional software. Temperature sensors begin to work with a significant increase or decrease in temperature, when it goes beyond the permissible limits. And the ABS system is usually responsible for controlling the speed of rotation, so these sensors are initialized through it.

Signals from the sensor do not go constantly, but at certain intervals. In most TPMS systems, the time interval is on the order of 60, however, in some systems, as the speed increases, the frequency of the signal, up to 2 ... 3 seconds, also becomes more frequent.

From the transmitting antenna of each sensor, a radio signal of a certain frequency goes to the receiving device. The latter can be installed either in the passenger compartment or in the engine compartment. If the operating parameters in the wheel go beyond the permissible limits, the system sends an alarm to the dashboard or to the electronic control unit.

How to register (bind) sensors

There are three basic methods for binding a sensor to a receiving system element.

Seven methods for linking tire pressure sensors

• Automatic. In such systems, the receiving device after a certain run (for example, 50 kilometers) itself “sees” the sensors and registers them in its memory.
• Stationary. It directly depends on the specific manufacturer and is indicated in the instructions. To prescribe, you need to press a sequence of buttons or other actions.
• Binding is performed using special equipment.

also, many sensors are triggered automatically after the car starts to drive. for different manufacturers, the corresponding speed may vary, but usually it is 10 .... 20 kilometers per hour.

Tire Pressure Sensor Life

The service life of the sensor depends on many parameters. First of all, their quality. Original sensors “live” for about 5…7 years. After that, their battery is usually discharged. However, most cheap universal sensors work much less. Typically, their service life is two years. They may still have batteries, but their cases crumble and they begin to “fail”. Naturally, if any sensor is mechanically damaged, its service life can be drastically reduced.

tire pressure sensors failure

Regardless of the manufacturer, in most cases, sensor failures are typical. namely, the following failures of the tire pressure sensor may occur:

• Battery failure. This is one of the most common reasons why a car tire pressure sensor does not work. The battery can simply lose its charge (especially if the sensor is already old).
• Antenna damage. Often, the pressure sensor antenna is a metal cap on the wheel nipple. If the cap is mechanically damaged, then the signal from it may either not come at all, or it may come in an incorrect form.

• Hit on the sensor of technological compositions. The performance of a car tire pressure sensor depends on its cleanliness. namely, do not allow chemicals from the road or just dirt, tire conditioner or other means designed to protect tires to get on the sensor housing.
• Sensor damage. Its body must necessarily be screwed to the valve stem of the nipple. The TPMS sensor can be damaged as a result of an accident, unsuccessful wheel repair, a car hitting a critical obstacle, well, or simply because of unsuccessful installation / dismantling. When disassembling a wheel at a tire shop, always warn workers about the presence of sensors!
• Sticking of the cap on the thread. Some transducers only use a plastic outer cap. They have radio transmitters inside. Therefore, metal caps cannot be screwed on them, since it is likely that they will simply stick to the sensor tube under the influence of moisture and chemicals and it will be impossible to unscrew them. In this case, they are simply cut off and, in fact, the sensor fails.
• Depressurization of the sensor nipple. This often happens when installing sensors if a sealing nylon washer was not installed between the nipple and the inner rubber band, or instead of a metal washer instead of a nylon washer. As a result of incorrect installation, permanent air etching appears. And in the latter case, it is also possible for the puck to stick to the nipple. Then you have to cut the nut, change the fitting.

How to check tire pressure sensors

Checking the wheel pressure sensor begins with a check with a pressure gauge. If the pressure gauge shows that the pressure in the tire is different from the nominal, pump it up. When the sensor still behaves incorrectly after that or the error does not go away, you can use the program or a special device, and then dismantle it and perform further checks.

Please note that before removing the sensor from the wheel, air must be released from the tire. And you need to do this on a posted wheel. That is, in garage conditions, with the help of a jack, you need to hang the wheels in turn.

How to identify a faulty tire pressure sensor

First of all, you need to check the performance of the sensors. To do this, you need to start the internal combustion engine and see if the tire pressure warning light on the dashboard is on or off. In some cars, the ECU is responsible for this. A warning will also appear on the panel indicating a specific sensor that indicates incorrect pressure or the complete absence of a signal. However, not all cars have a lamp indicating problems with the tire pressure sensor. On many, the relevant information is given directly to the electronic control unit, and then an error appears. And only after that it is worth doing a software check of the sensors.

For ordinary motorists, there is a convenient way to check tire pressure without a pressure gauge. To do this, you need to use the scanning device ELM 327 version 1,5 and higher. The verification algorithm is as follows:

Screenshot of the HobDrive program. How can I find out a faulty tire sensor

• you need to download and install the free version of the HobDrive program on a mobile gadget to work with a specific car.
• Using the program, you need to “contact” with the diagnostic tool.
• Go to program settings. To do this, first launch the “Screens” function, and then “Settings”.
• In this menu, you need to select the “Vehicle parameters” function. next - "ECU settings".
• In the ECU type line, you need to select the car model and version of its software, and then click on the OK button, thereby saving the selected settings.
• Next, you need to set the parameters of the tire sensors. To do this, go to the "TPMS parameters" function.
• Then on “Type” and “Missing or built-in TPMS”. This will set up the program.
• then, to check the tires, you need to go back to the “Screens” menu and press the “Tire pressure” button.
• Information will appear on the screen in the form of a picture about the pressure in a particular tire of the car, as well as the temperature in it.
• also in the “Screens” function, you can view information about each sensor, namely, its ID.
• If the program does not provide information about some sensor, then this is the “culprit” of the error.

For cars manufactured by VAG for a similar purpose, you can use the Vasya Diagnostic program (VagCom). The verification algorithm is performed as follows:

• One sensor must be left in the spare wheel and placed in the trunk. The front two must be placed in the cabin near the driver's and passenger's doors, respectively. Rear sensors need to be placed in different corners of the trunk, right and left, closer to the wheels.
• To check the condition of the batteries, you need to start the internal combustion engine or simply turn on the engine ignition. then you need to go to the controller number 65 from the first to the 16th group. There are three groups per sensor. If all is well, the program will show zero pressure, temperature and sensor battery status.
• You can check in the same way how correctly the sensors respond to temperature. For example, putting them alternately under a warm deflector, or in a cold trunk.
• To check the condition of the batteries, you need to go to the same controller number 65, namely, groups 002, 005, 008, 011, 014. There, the information shows how much each battery supposedly left to function in months. By comparing this information with the given temperature, you can make the best decision to replace one or another sensor or just the battery.

Checking the battery

At the removed sensor, the first thing to do is to check its battery (battery). According to statistics, it is for this problem that the sensor most often stops working. Typically, the battery is built into the sensor body and is closed with a protective cover. However, there are sensors with a completely sealed case, that is, in which battery replacement is not provided. It is understood that such sensors need to be changed completely. Typically, European and American sensors are non-separable, while Korean and Japanese sensors are collapsible, that is, they can change the battery.

Accordingly, if the case is collapsible, then, depending on the design of the sensor, it must be disassembled and the battery removed. After that, replace it with a new one, and check the operation of the tire pressure sensor. If not collapsible, then you will either have to change it, or open the case and pull out the battery, and then glue the case again.

Flat batteries "tablets" with a nominal voltage of 3 volts. However, new batteries usually give out a voltage of about 3,3 volts, and as practice shows, the pressure sensor can “fail” when the battery is discharged to 2,9 volts.

Relevant for sensors that ride on one element for about five years and more, up to 7 ... 10 years. When installing a new sensor, it usually needs to be initialized. This is done by software, depending on the specific system.

Visual inspection

When checking, be sure to check the sensor visually. namely, to examine whether its body is chipped, cracked, whether any part is broken off. Particular attention must be paid to the integrity of the cap on the nipple, since, as mentioned above, in most designs it serves as a transmitting antenna. If the cap is damaged, it must be replaced with a new one. If the sensor housing is damaged, the chances of restoring performance are much less.

Pressure test

TPMS sensors can also be tested using specially designed tools. namely, there are special metal pressure chambers at tire shops, which are hermetically sealed. They contain the tested sensors. And on the side of the box is a rubber hose with a nipple for pumping air into its volume.

A similar design can be built independently. For example, from a glass or plastic bottle with a hermetically sealed lid. And place the sensor in it, and attach a similarly sealed hose with a nipple. However, the problem here is that, firstly, this sensor must transmit a signal to the monitor. If there is no monitor, such a check is impossible. And secondly, you need to know the technical parameters of the sensor and the features of its operation.

Verification by specialized means

Specialized services often have special hardware and software for checking tire pressure sensors. One of the most popular are diagnostic scanners for checking pressure and pressure sensors from Autel. For example, one of the simplest models is Autel TS408 TPMS. With it, you can activate and diagnose almost any pressure sensor. namely, its health, battery status, temperature, change settings and program settings.

However, the disadvantage of such devices is obvious - their high price. For example, the basic model of this device, as of spring 2020, is about 25 thousand Russian rubles.

Tire pressure sensor repair

Repair measures will depend on the reasons why the sensor failed. The most common type of self-repair is battery replacement. As mentioned above, most sensors have a non-separable housing, so it is understood that the battery cannot be replaced in them.

If the sensor housing is non-separable, then it can be opened in two ways to replace the battery. The first is to cut, the second is to melt, for example, with a soldering iron. You can cut it with a hacksaw, a hand jigsaw, a powerful knife or similar items. It is necessary to use a soldering iron to melt the plastic of the housing very carefully, especially if the sensor housing is small. It is better to use a small and weak soldering iron. Replacing the battery itself is not difficult. The main thing is not to confuse the battery brand and polarity. After replacing the battery, do not forget that the sensor must be initialized in the system. Sometimes this happens automatically, but in most cases it happens because of this, for specific cars, an algorithm.

According to statistics, on Kia and Hyundai cars, original tire pressure sensors last no more than five years. Even further replacement of batteries often does not help. Accordingly, they are usually replaced with new ones.

When dismantling the tire, pressure sensors often damage the nipple. One way to solve this problem is to cut threads on the inner surface of the nipple with a tap. Usually this is a 6 mm thread. And accordingly, then you need to take the nipple from the old camera and cut off all the rubber from it. further on it, similarly, cut an external thread of the same diameter and pitch. And combine these two obtained details. In this case, it is desirable to treat the structure with a sealant.

If your car was not originally equipped with tire pressure sensors, then there are universal systems that can be purchased and installed additionally. However, as experts note, usually such systems, and accordingly, the sensors are short-lived. In addition, when installing a new sensor in the wheel, it needs to be rebalanced! Therefore, for installation and balancing, it is imperative to seek help from a tire fitting, since the appropriate equipment is only there.

Hack and predictor Aviator

First of all, what needs to be checked at the tire pressure sensor is the battery. Especially if the sensor has been in service for more than five years. It is best to check the sensor using specialized tools. When replacing a sensor with a new one, it is necessary to “register” it in the system so that it “sees” it and works correctly. And do not forget, when changing tires, to warn the tire fitting worker that a pressure sensor is installed in the wheel.