Tyre pressure monitoring system
Here you will find useful information and important tips relating to tyre pressure monitoring systems in vehicles.
Important safety note
Tyre pressure is an essential safety factor of a vehicle. The most common tyre damage can be traced back to a gradual pressure loss. This is often noticed by the driver of the vehicle when it is too late. Insufficient tyre pressure causes increased fuel consumption and poor driving characteristics. Increased tyre temperature and greater wear are also linked to this. Insufficient tyre pressure may cause the tyre to suddenly burst. This is an extremely high safety risk for all those in the vehicle. This is why tyre pressure monitoring systems (TPMS) have been mandatory since November 2014 for all new vehicles in the EU.
The general parts aftermarket also offers different systems for retrofitting. Tyre pressure monitoring systems monitor the tyre pressure and tyre temperature. Tyre pressure monitoring systems have been on the market for a while, mostly in top-end vehicles. In the USA, they have been mandatory for new vehicles for several years. It is therefore time for all workshop staff to familiarise themselves with this topic. because even during a wheel change, a lack of knowledge about the systems can lead to impairment of the tyre pressure monitoring system.
We differentiate between two fundamentally different systems: Indirect and direct tyre pressure monitoring systems.
In indirect measuring systems, the pressure is monitored using ABS sensors on the vehicle. The ABS control unit detects the pressure loss of a tyre through the different rolling circumference. A tyre with a low air pressure makes more revolutions than one with the correct air pressure. However, these systems are not as precise as direct measurement systems, and require a pressure loss of approx. 30% before there is a warning message.
The advantage is the relatively low price as numerous vehicle components already in place can be used. The only things required are adapted ABS software and an additional display in the instrument unit.
Direct measurement systems are considerably more precise, but also involve more outlay, and are therefore more expensive. Here, a battery-powered sensor is located in each wheel. This measures the temperature and the pressure of the tyre, and transfers the measured values wirelessly to the tyre pressure monitoring system control unit and/or the display unit. One or more antennas transmit the radio signal.
Direct systems compare the tyre pressure with a reference value stored in the tyre pressure monitoring system control unit. This has the advantage that pressure losses of several tyres can be detected at the same time. This may mean that, following a tyre change, a re-adjustment (calibration) or re-coding of the sensors is required.
A further disadvantage of the direct measuring systems is that the batteries have to be replaced after approx. 5 – 10 years. As, depending on the manufacturer, these form a unit with the sensors, this often means complete replacement of the sensor unit.
If the batteries have to be replaced, this is shown in a timely manner by the display unit, meaning that a sudden system failure is avoided. When changing from summer to winter tyres, it should be ensured that additional wheel sensors are attached, or that existing sensors are modified. Certain important points should be noted so that no damage or functional problems occur during tyre fitting.
Before changing a wheel or tyre, you should always check to what extent the vehicle has a tyre pressure monitoring system. This can be ascertained, for example, from a coloured valve, a coloured valve cap, a symbol in the instrument cluster, or an additional display unit (for retrofitted systems). It is recommended that you ask the customer about any tyre pressure monitoring systems directly during vehicle handover and point out the special features.
For active systems, the following points must be observed:
As there are numerous systems on the market which operate differently, the manufacturer-specific installation instructions must also be observed if possible.
|TSS||Beru||Tyre Safety System – direct measurement
Tyre pressure monitoring system with four separate antennas
|Audi, Bentley, BMW, Ferrari, Land Rover, Maserati, Maybach, Mercedes, Porsche, VW, commercial vehicles|
|SMSP||Schrader, sales in Germany: Tecma||Direct measurement tyre pressure monitoring system with a central antenna||Citroen, Vauxhall, Peugeot, Renault, Chevrolet, Cadillac|
|DDS||Continental Teves||Deflection Detection System – indirect measurement tyre pressure monitoring system||BMW, Mini, Vauxhall|
|TPMS||Continental Teves||Tyre Pressure Monitoring System – direct measurement tyre pressure monitoring system||Vauxhall|
|VDO||BMW, Citroen, Fiat, Ford, Honda, Hyundai, Infiniti, Jaguar, Jeep, Kia, Lada, Lancia, Land Rover, Mazda, Mercedes Bens, Mini, Mitsubichi, Nissan, Peugeot, Renault, Suzuki, Tesla, Volkswagen, Volvo|
|Warn Air||Dunlop||Indirect measurement tyre pressure monitoring system||BMW, Mini|
|Tyre Guard||Siemens VDO||Direct measurement tyre pressure monitoring system with a sensor which has been permanently integrated into the tyres without a battery||Renault|
|Smar Tyre||Sales: Seehase||Direct measurement tyre pressure monitoring system for retrofitting||Universal|
|X-Pressure||Pirelli||Direct measurement tyre pressure monitoring system for retrofitting||Universal|
|Road Snoop||Nokian||Direct measurement tyre pressure monitoring system for retrofitting||Universal|
|Magic Control||Waeco||Direct measurement tyre pressure monitoring system for retrofitting||Universal|
No liability assumed
The TSS from Beru is installed in series by many vehicle manufacturers, but is also offered as an accessory for retrofitting. BMW calls the Beru system "RDC" (Reifen Druck Control, or Tyre Pressure Control); at Mercedes and Audi it is the "tyre pressure control system". It comprises four aluminium valves, four wheel electronics systems (wheel sensors), and four antennas, and a control unit (with an additional spare wheel monitoring system, five of each). The wheel electronics and valve are mounted on the rim. The radio receivers are located in the wheel well. For systems installed in series, the display unit is integrated in the instrument cluster.
Fig. 1 shows the individual components of the system:
For retrofitted systems, a separate display unit is installed. During removal/mounting of the wheels/tyres, the points mentioned previously must be observed. In the event of visible damage to the housing, or if the filter surface is dirty, the wheel electronics must be replaced.
The complete valve must be replaced when
The wheel electronics and
Following a wheel/tyre change, changing of the wheel position, replacement of the wheel sensor system, or a deliberate change to the tyre pressure (e.g. when the vehicle is fully loaded), the new pressures are taken over by the TSS. For this, all of the tyres must first of all be filled with the prescribed or specially selected pressure. By pressing the calibration button, the values are saved. The system then checks whether the pressures are realistic (e.g. the minimum pressure or the differences between left and right). If the wheels are transported in the boot of the vehicle concerned, for example for seasonal changing of the wheels, they are within range of the control unit. If the wheels being replaced have already been input into the system instead of the usual four (five with spare wheel), the control unit now receives eight or nine signals. In this case, the system reports that it is "not available".
The same thing can happen when unloaded wheels or the wheels of another vehicle (which also has a tyre pressure monitoring system) are located in the vicinity. Please also make the customer aware that the system must then be re-calibrated again. Calibration of the series TSS is vehicle specific. Instructions for this can be found on the web pages of Beru.
Diagnostic units such as the Hella Gutmann mega macs 77 are also able to read out the fault memory and the actual values of the tyre pressure monitoring systems, and to delete any fault codes.
Many vehicle systems additionally provide digital measured values as parameters to enable fast diagnosis. Parameters indicate the current status or setpoint and actual values of the component. In this section, you can, for instance, access information about the current tyre pressure.
Additional information relating to maintenance and repair can be obtained in the vehicle information, depending on the vehicle model and system.
The respective test depth and variety of functions can be set out differently depending on the vehicle manufacturer and is dependent on the relevant system configuration of the control unit.
For all of the monitoring technologies, one thing should not be forgotten. A tyre pressure monitoring system does not correct the tyre pressure itself and does not provide any information on the age or the tread depth of a tyre. This means that in the future, too, it will be essential to regularly monitor the tyre as the most important connection between the vehicle and the road.
For the purpose of an example, the following information is illustrated using a Mercedes-Benz W 212 E350 featuring direct tyre pressure monitoring system. This vehicle features sensors on all four wheels that forward the tyre pressure to a superordinate system. The tyre pressure monitoring system monitors the tyre pressure using the data from the wheel speed sensors. If a pressure drop is identified on one of the tyres, drivers are visually warned by a notification on the multi-function display indicating "tyre pressure loss" on the instrument cluster.
The display shows the current tyre pressure of individual wheels (Figure 3). If the vehicle has not been moved for a prolonged period of time prior to the check, the display indicates "Tyre pressure monitoring appears after a few minutes of driving time".
In the following cases it is necessary to carry out basic tyre pressure value setting in the system:
The following warning messages appear on the display:
Park the vehicle in a safe location and engage the parking brake.
After a few minutes of driving the system checks the new tyre pressures and subsequently saves them as the new reference values. Alternatively it is possible to adjust the basic setting using a suitable diagnostic unit. The tyre pressure monitoring system automatically detects this following the calibration process.
In this vehicle model the vehicle manufacturer's recommended tyre pressures have been listed on a sticker in the tank flap or in the operating manual. If an incorrect tyre pressure is set and activated, the system will monitor the incorrect pressure!
The tyre pressure monitoring system function may be impaired or delayed in the following cases.
The following information is illustrated using a Mazda CX-5 featuring indirect tyre pressure monitoring system as an example. The system records the tyre pressure of all four wheels. The ABS control unit determines the tyre pressure on the basis of the data from wheel speed sensors. Drivers are visually and audibly warned if a drop in pressure is detected at one of the tyres. The system must be initialised with the prescribed tyre pressure to guarantee the system operates correctly.
Re-initialise the system in the following cases.
Park the vehicle in a safe location and engage the parking brake.
In this vehicle model the manufacturer's recommended tyre pressures have been listed on a sticker on the driver's side B-pillar or in the operating manual. The principle to calibrate winter tyres is identical as this vehicle does not feature TPMS sensors.
Warning messages may be output in the following cases because the system may identify changes to the tyre condition.
On March 10, 2009 the European Parliament in Strasbourg officially adopted a proposed directive (EC no. 661/2009) put forward by the Commission to make motor vehicle homologation easier in Europe. In this process, the directive also included a mandatory introduction of previously mentioned technologies including a tyre pressure monitoring system (TPMS). "Category M1/M1G vehicles shall be equipped with an accurate tyre pressure monitoring system capable of outputting an in-car warning to the driver when a loss of pressure occurs in any tyre, in the interests of optimum fuel consumption and road safety. The implementation process was carried out in stages: from November 2012 a tyre pressure monitoring system has been mandatory in all newly homologated vehicle types and this has applied to all newly registered vehicles from November 2014.
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