tire pressure monitoring system
Here you will find useful information and important tips relating to tire pressure monitoring systems in vehicles.
Important safety note
tire pressure is an essential safety factor of a vehicle. The most common tire 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 tire pressure causes increased fuel consumption and poor driving characteristics. Increased tire temperature and greater wear are also linked to this. Insufficient tire pressure may cause the tire to suddenly burst. This is an extremely high safety risk for all those in the vehicle. This is why tire 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. tire pressure monitoring systems monitor the tire pressure and tire temperature. tire 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 tire pressure monitoring system.
We differentiate between two fundamentally different systems: Indirect and direct tire 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 tire through the different rolling circumference. A tire 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 tire, and transfers the measured values wirelessly to the tire pressure monitoring system control unit and/or the display unit. One or more antennas transmit the radio signal.
Direct systems compare the tire pressure with a reference value stored in the tire pressure monitoring system control unit. This has the advantage that pressure losses of several tires can be detected at the same time. This may mean that, following a tire 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 tires, 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 tire fitting.
Before changing a wheel or tire, you should always check to what extent the vehicle has a tire 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 tire 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||tire Safety System – direct measurement |
tire 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 tire pressure monitoring system with a central antenna||Citroen, Opel, Peugeot, Renault, Chevrolet, Cadillac|
|DDS||Continental Teves||Deflection Detection System – indirect measurement tire pressure monitoring system||BMW, Mini, Opel|
|TPMS||Continental Teves||tire Pressure Monitoring System – direct measurement tire pressure monitoring system||Opel/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 tire pressure monitoring system||BMW, Mini|
|tire Guard||Siemens VDO||Direct measurement tire pressure monitoring system with a sensor which has been permanently integrated into the tires without a battery||Renault|
|Smar tire||Sales: Seehase||Direct measurement tire pressure monitoring system for retrofitting||Universal|
|X-Pressure||Pirelli||Direct measurement tire pressure monitoring system for retrofitting||Universal|
|Road Snoop||Nokian||Direct measurement tire pressure monitoring system for retrofitting||Universal|
|Magic Control||Waeco||Direct measurement tire 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 tire Pressure Control); at Mercedes and Audi it is the "tire 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/tires, 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/tire change, changing of the wheel position, replacement of the wheel sensor system, or a deliberate change to the tire pressure (e.g. when the vehicle is fully loaded), the new pressures are taken over by the TSS. For this, all of the tires 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 tire 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 tire 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 tire 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 tire pressure monitoring system does not correct the tire pressure itself and does not provide any information on the age or the tread depth of a tire. This means that in the future, too, it will be essential to regularly monitor the tire 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 tire pressure monitoring system. This vehicle features sensors on all four wheels that forward the tire pressure to a superordinate system. The tire pressure monitoring system monitors the tire pressure using the data from the wheel speed sensors. If a pressure drop is identified on one of the tires, drivers are visually warned by a notification on the multi-function display indicating "tire pressure loss" on the instrument cluster.
The display shows the current tire 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 "tire pressure monitoring appears after a few minutes of driving time".
In the following cases it is necessary to carry out basic tire 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 tire 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 tire pressure monitoring system automatically detects this following the calibration process.
In this vehicle model the vehicle manufacturer's recommended tire pressures have been listed on a sticker in the tank flap or in the operating manual. If an incorrect tire pressure is set and activated, the system will monitor the incorrect pressure!
The tire 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 tire pressure monitoring system as an example. The system records the tire pressure of all four wheels. The ABS control unit determines the tire 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 tires. The system must be initialised with the prescribed tire 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 tire pressures have been listed on a sticker on the driver's side B-pillar or in the operating manual. The principle to calibrate winter tires 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 tire 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 tire pressure monitoring system (TPMS). "Category M1/M1G vehicles shall be equipped with an accurate tire pressure monitoring system capable of outputting an in-car warning to the driver when a loss of pressure occurs in any tire, in the interests of optimum fuel consumption and road safety. The implementation process was carried out in stages: from November 2012 a tire 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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