All about TPMS: what is the abbreviation, what is it responsible for and what types are there
The abbreviation TPMS is not as popular as ABS or automatic transmission, but today it is an integral part of almost any modern car.
TPMS is a tire pressure monitoring system. It stands for “tire pressure monitoring system”. Sometimes you can find variations such as iTPMS and dTPMS. The meaning of such abbreviations will be discussed in detail below.
How to check for TPMS
There are two ways to find out if your vehicle has a tire pressure monitoring system.
1. Check for the presence of the TPMS system via the car’s multimedia interface. The best thing to do in this case would be to refer to the operating manual for a detailed algorithm of actions.
If you don’t have one at hand, you should study the on-board computer menu. If there is a factory TPMS, one of the settings sections will definitely be dedicated to this system.
The key phrases to look for are: “tire pressure monitoring”, “pressure monitoring system” and similar phrases. Also, one of the sure signs of its presence will be a button with a corresponding icon on the dashboard or elsewhere – for example, the central tunnel between the seats.
It is important to note that the reverse logic of the button’s connection with the pressure monitoring system is in effect here. That is, the presence of a button 100% indicates the presence of TPMS in the car, but not every TPMS has an output to the button – many factory systems are configured through the on-board computer menu.
2. Check for pressure sensors directly. If the direct-action electronic TPMS system has internal sensors, they can only be detected by removing the tire from the disk. In some cases, such a sensor can be identified by the outer part of the inflation valve.
If the TPMS is equipped with external sensors, everything is much simpler – they are screwed onto the outer part of the valve instead of protective caps. Then all that remains is to find the receiving device (screen) that comes with the sensors.
How Works
Obviously, the primary task of a tire monitoring system is to warn the driver in advance of a drop in pressure in order to prevent wear or damage to the tires. However, the operating principle of the systems can differ dramatically.
The simplest TPMS variants do not have sensors. Consequently, there is no “knowledge” about the actual tire pressure. They can only inform that it has become higher or lower than the established norm (how the system understands this will be described below).
The norm is set by the driver himself, having previously made sure that all 4 wheels are inflated to the required and equal pressure. After that, he informs the system – via the standard on-board computer or the very button mentioned earlier – that the values are currently standard. Then the electronics start from the specified parameters and inform about deviations.
More advanced options display specific pressure values for each wheel. Subtypes of such TPMS systems are those with either radio sensors in the valves (internal or external) or with simple mechanical barometers that screw on instead of caps.
Radio sensors display values with an accuracy of tenths of a bar. But screw-on mechanical micromanometers are more of a decorative ornament. They are only good for a very rough understanding of the degree of tire inflation with a large margin of error. And, as a rule, they do not last very long.
How to set up TPMS
The solution to this issue is possible after understanding the type of system the owner is dealing with. If the pressure monitoring system is built into the car’s electronics (i.e., factory), the process will be intuitive.
If the TPMS is installed as additional equipment, the most reasonable thing to do is to consult its operating manual. Therefore, below we will describe only the most basic and universal recommendations that do not relate to a specific system.
If TPMS is factory
Make sure that the pressure in all tires is the same.
Press and hold the button with the TPMS symbol (if there is one), or select the appropriate item (for example, “setting the pressure value”) in the on-board computer menu.
In response to the on-board computer request, confirm the installation of the current parameters as normal.
If TPMS is not factory
Make sure that the pressure in all tires is the same.
Turn on the receiving device. Usually this is a screen powered by a USB port or cigarette lighter socket. There are options with wiring and even with solar cells.
Go to the receiver menu in the sensor binding mode – so that the head unit knows which sensor is responsible for which wheel.
If the transmitters (the pressure sensors themselves) are external, they must be screwed onto the wheels in the order specified in the instructions. In this way, the receiver will bind each sensor in accordance with the wheel on which it was screwed.
If the TPMS sensors are internal, then during the process of binding each of them you will have to either press the valve to sharply reduce the pressure (so that the sensor “wakes up” and sends a signal to the receiver), or bind each of the wheels while driving. In order not to go through the procedure of binding sensors each time again (for example, when rearranging the wheels from the front axle to the rear), the device menu usually has the ability to virtually change the position of each wheel.
Let us repeat that each specific TPMS model will have its own sequence of actions, and the above algorithm is provided for a general understanding of the procedure.
Types of TPMS
Although there is a huge selection of tire pressure monitoring systems available today, they can all be divided into two fundamentally different groups.
Direct Tire Pressure Monitoring System (dTPMS).
The prefix “d” means “direct” – “direct” or “immediate”. In such a system, the receiving device to which the data is output receives a direct signal from each sensor located in the wheel. The values are displayed in bars (accurate to tenths), and the system is capable of responding very quickly to pressure changes: each sensor is polled up to ten times per second.
Sometimes the interval is shorter, but it is still more than enough to promptly warn the driver about a drop in pressure in one of the wheels. Factory dTPMS systems are equipped exclusively with internal sensors installed at the tire shop.
Various cheap devices with external sensors screwed onto the wheel valve from the outside also formally belong to direct TPMS. But often the accuracy, speed and durability of such kits leave much to be desired.
A truly high-quality system always has internal sensors installed on the disk from the inside – with high accuracy of readings, high reliability and batteries that last up to 8-10 years.
Indirect Tire Pressure Monitoring System – iTPMS
Despite the very similar name, the prefix “i” changes everything. It means “indirect” – “indirect”. Such a system does not have sensors in the wheels, but is guided by the readings of the car sensors, namely the ABS/ESP system sensors.
The lower the pressure in the wheel, the smaller its radius. This means that at a constant speed, the deflating wheel will make more revolutions per minute than the others.
This difference is registered by the ABS/ESP unit, which issues a warning on the on-board computer screen. The main problem with indirect iTPMS is not even that they do not indicate the specific pressure in each of the wheels.
The main disadvantage of such systems is their very low response speed. It takes from one to several minutes for the ABS/ESP unit to “understand” that a constant alarm signal from one of the wheels is a consequence of pressure drop, and not slippage.
During this time, if the wheel is significantly damaged, it will have already had time to wear out noticeably. Unless, of course, the driver himself notices changes in the car’s behavior.
TPMS error
If you don’t take into account cheap Chinese no-name kits, any dTPMS system is very reliable. And if it is an indirect iTPMS, then it can be considered eternal: the service life is actually equal to the service life of the sensors of the standard ABS/ESP system, and they are extremely durable.
In a direct tire pressure monitoring system (dTPMS), there are essentially only two possible types of errors: either a loss of connection with one or more sensors, or a malfunction of the receiving device itself. In the first case, the cause, as a rule, lies in the dead batteries of the sensors.
On expensive branded systems, they are often declared as non-replaceable and filled with compound, which forces the owner to fork out for a new set.
But with a certain skill, the batteries can be replaced. The main thing is not to skimp on a high-quality power supply element and properly seal the place of “surgical intervention” on the case. If the reason for the loss of connection lies in the malfunction of the sensor or receiver itself, with a high degree of probability, nothing can be done except replace them.
As for warnings displayed on the screen, they are not errors as such. Usually, these are notifications related either to a drop in pressure in one of the wheels (the actual purpose of any TPMS), or to other functions of the system.
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