Tyre pressure monitoring system (TPMS)

From the end of 2014, all new vehicles have a tyre pressure monitoring system on board as standard. It provides a warning about insufficient tyre pressure and protects the driver against increased fuel consumption and tyre damage. On this page, those interested in technology will find a whole host of details relating to the respective system variants, practical tips for changing tyres, and important information to be taken into account during tyre fitting.

The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for suitably qualified personnel only.

Tyre pressure monitoring system

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.

Indirect tyre pressure monitoring system

Indirect tire pressure monitoring system

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 tyre pressure monitoring system

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.

What should you pay attention to during wheel and 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.

What to look out for when fitting wheels / tires? — Fig.1

For active systems, the following points must be observed:

During removal of the tyre, the removal lever must only be applied on the opposite side to the valve on both sides of the tyre ( Fig. 1 ).
When dismounting the tyre, the mounting head must be placed approx. 15 cm behind the valve ( Fig. 2 ).
Avoid any force being applied to the sensor.
During removal and mounting of the tyre, tyre bead and rim flange may only be wetted with mounting spray or soap solution. Using mounting paste may cause the filter surface of the sensor electronics to clog.
The sensor may only be cleaned with a dry, lint-free cloth. Compressed air, cleaning agents, and solvents must not be used.
Before mounting a new tyre, the sensor unit must be checked for dirt, damage, and tight fit.
Replace the valve insert and/or the valve (depending on the manufacturer's specifications). Observe the tightening torques.
Following mounting, carry out calibration/re-coding with cold tyres if applicable.
Information from the vehicle and system manufacturers should be noted separately.

As there are numerous systems on the market which operate differently, the manufacturer-specific installation instructions must also be observed if possible

Tyre pressure monitoring systems

System	Manufacturer	Description	Used for
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, Nutzfahrzeuge
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
TPMS	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
Tire 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 Tire	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

Tyre safety system (tss) beru

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.

TSS BERU: Components of the tire pressure monitoring system — Fig. 1: 1 Wheel electronics, 2 Wheel electronics with tyre valve, 3 Retaining clips, 4 Antenna, 5 Control unit

TSS BERU: Assembly of the wheel electronics — Fig. 2: 1 Self-locking fixing screw, 2 Wheel electronics housing, 3 Valve, 4 Spacer, 5 Union nut, 6 Valve cap, 7 Mounting pin

Fig. 1 shows the individual components of the system:

Wheel electronics (1)
Wheel electronics with tyre valve (2)
Retaining clips (3)
Antenna (4)
Control unit (5)

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 are replaced
the self-locking (Torx) fixing screw and/or the union nut of the valve is loose (do not retighten)
the contact points of the wheel electronics protrude by more than one millimeter

The wheel electronics and

tyre valve can easily be assembled and mounted using Fig. 2 :
Insert self-locking fixing screw (1) through the housing of the wheel electronics (2) and screw into the valve with two to three turns.
Slide valve (3) through the valve hole bore in the rim, put on spacer (4), and screw on union nut (5) until it lies against the spacer.
Insert mounting pin (7) into the radial bore of the valve, and tighten union nut with a torque of 3.5 – 4.5 Nm. Remove the mounting pin otherwise the tyre will become damaged during further mounting.
Lightly press the wheel electronics into the rim well. The contact points must lie flat in the well. Then tighten the fixing screw with a torque
of 3.5 – 4.5 Nm.
Following tyre fitting, screw on the valve cap (6).

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.

If the spare wheel is also to be monitored by the tyre pressure monitoring system, following removal, it should be installed again in the precise location it was in before. Especially during an inspection or following a pressure test, for the BMW E60, E65, for example, it should be ensured that the tyre valve is at the 9 o'clock position again following installation of the spare wheel. The receiver only detects signals from the transmitter in this position.

French vehicle manufacturers in particular use the SMSP system from Schrader. This is different in that it only has one radio receiver (antenna).

The position of the wheels is distinguished using colour identification on the valves:

Green ring = front left
Yellow ring = front right
Red ring = rear left
Black ring = rear right

Following tyre fitting or replacement of a sensor, it may be necessary to code the sensors as a difference in position of the wheels may not be detected with just one antenna or because the wireless connection was interrupted. As the electronics in this system only measure the pressure every 15 minutes during vehicle standstill and only transfer the measured values once an hour to the control unit, for the coding, you need a diagnostic unit as well as a so-called "valve exciter".

It prompts the wheel sensor system to transmit the measured values to the control unit via radio.

Display of the Audi TT tire pressure parameters — Audi TT tyre pressure parameter illustration

Repair information VW Passat — VW Passat repair information

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.

Following removal of the wheels (e.g. during brake repairs ) these must be re-installed in the location they were in originally. Tyre pressure monitoring system display faults may otherwise be the result (e.g. Renault Laguna 2).

For almost all tyre pressure monitoring systems, transmission occurs in the frequency range of 433 MHz. This frequency range is also, however, used by radio devices, radio headphones, alarm systems, and garage door drives, for example. Please take this into account in the event of malfunctions with the tyre pressure monitoring system. The current development is toward small active systems without batteries (transponder technology) which are just glued into the carcass or which are integrated into the tyre. These systems operate in the 2.4 GHz range, which is not so susceptible to interference, and can record other information, such as road condition and wear state, in addition to temperature and pressure values.

Today, tyre pressure monitoring systems are as common a part of vehicle equipment as ABS or the air-conditioning system .

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

Direct tyre pressure monitoring system - example Mercedes-Benz W212 E350

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.

TPMS: Displaying the tire pressure in the multifunction display Fig. 1 — Figure 1: Press the "Right arrow" system selection button on the steering wheel until SERVICE is shown on the display

TPMS: Displaying the tire pressure in the multifunction display Fig. 2 — Figure 2: Press the "Down arrow" button until "Tyre pressure" appears on the display

TPMS: Displaying the tire pressure in the multifunction display Fig. 3 — Figure 3: The current tyre pressure of individual wheels is shown on the display

Tyre pressure illustration on the multi-function display

Switch on the ignition
Press the "Right arrow" system selection button on the steering wheel until SERVICE appears on the display ( Figure 1 ).
Confirm the input with "OK".
Press the "Down arrow" button until "Tyre pressure" is shown on the display ( Figure 2 ).
Confirm the input with "OK".

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".

Adjusting and saving the tyre pressure in the system

In the following cases it is necessary to carry out basic tyre pressure value setting in the system:

A tyre pressure monitoring system warning message has been activated.
The tyre pressure has been changed or adjusted.
Tyres or wheels have been installed in different positions or they have been replaced.
Battery disconnected or replaced.

The following warning messages appear on the display:

"Correct tyre pressure". The tyre pressure of at least one tyre is too low and must be re-inflated from time to time
"Check tyre pressure". The tyre pressure at one or more tyres has dropped significantly
"Caution: tyre faulty". The tyre pressure at one or more tyres has suddenly dropped significantly

TPMS: Initialization procedure — Figure 4: "Tyre pressure OK now?" appears on the display

Initialisation process

Park the vehicle in a safe location and engage the parking brake.

Check the tyre pressure of all four wheels as per manufacturer instructions and correct, if necessary.
Switch on the ignition.
Press the "Right arrow" system selection button on the steering wheel until SERVICE appears on the display.
Confirm input with "OK".
Press the "Down arrow" button until the "Tyre pressure monitoring system active"notification appears on the display.
Confirm input with "OK".
"Tyre pressure OK now?" shown on the display ( Figure 4 ).
Select "YES" and confirm.
"Tyre pressure monitoring system restarted" appears on the display.

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

Maintenance information

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.

Snow chains have been fitted to the vehicle
Vehicle is being driven on unsurfaced roads
Driving with a heavily loaded trailer
Sporty driving style, severe acceleration or braking on routes with many corners
One-sided loading as a result of having overloaded one side of the vehicle

With regard to this, please always observe the respective maintenance and repair notes provided by the vehicle manufacturer

Indirect tyre pressure monitoring system - example: Mazda CX-5

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.

Adjusting and saving the tyre pressure in the system

Re-initialise the system in the following cases.

Tyre pressure has been corrected.
One of the tyres has been replaced.
The position of tyres on the vehicle has been changed.
The ABS control unit has been replaced or disconnected.
The battery has been disconnected or replaced.
The tyre pressure monitoring system warning light is on.

Initialisation process

Park the vehicle in a safe location and engage the parking brake.

Check the tyre pressure of all four wheels as per manufacturer instructions and correct, if necessary.
Switch on the ignition.
Press the SET button until the TPMS warning lamp on the dashboard flashes twice and an audible warning is output ( Figure 5 ).
"Tyre pressure monitor initialised" appears on the display ( Figure 6 ).
Subsequently take the vehicle for a test drive to complete the process.

Maintenance information!

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.

Causes of failure

Warning messages may be output in the following cases because the system may identify changes to the tyre condition.

A tyre pressure value significantly above the prescribed value has been set
The wheel and tyre combination does not meet vehicle manufacturer specifications
Use of a space saver spare wheel or snow chains
Aggressive driving style, severe acceleration or braking on routes with many corners
One-sided loading as a result of having overloaded one side of the vehicle

With regard to this, please always observe the respective maintenance and repair notes provided by the vehicle manufacturer.

EU legislation on tyre pressure monitoring

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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