Tyre pressure monitoring system (TPMS)

Here you will find useful information and important tips relating to tyre pressure monitoring systems in vehicles.

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.

Important safety information
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 use by suitably qualified personnel only.

TABLE OF CONTENTS

Basic principles

Tyre pressure monitoring system

Function

Indirect tyre pressure monitoring systems

Function

Direct tyre pressure monitoring systems

Practical tips

What should you pay attention to during wheel and tyre fitting?

Overview

Tyre pressure monitoring systems

Workshop tips

Beru Tyre Safety System (TSS)

Good to know

EU legislation on tyre pressure monitoring

TYRE PRESSURE MONITORING SYSTEM: BASIC PRINCIPLES

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 every workshop to familiarise itself 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: FUNCTION

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.

Indirect tyre pressure monitoring systems

DIRECT TYRE PRESSURE MONITORING SYSTEM: FUNCTION

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 tire 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 tire fitting.

WHAT SHOULD YOU PAY ATTENTION TO DURING WHEEL AND TYRE FITTING?: PRACTICAL TIPS

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:

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 which operate differently on the market, the manufacturer-specific installation instructions should also be observed if possible.

Fig. 1

Fig. 2

TYRE PRESSURE MONITORING SYSTEMS: OVERVIEW

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, commercial vehicles
SMSP	Schrader, sales in Germany: Tecma	Direct measurement tyre pressure monitoring system with a central antenna	Citroen, Opel, Peugeot, Renault, Chevrolet, Cadillac
DDS	Continental Teves	Deflection Detection System – indirect measurement tyre pressure monitoring system	BMW, Mini, Opel
TPMS	Continental Teves	Tyre Pressure Monitoring System – direct measurement tyre pressure monitoring system	Opel
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 without a battery which is integrated firmly in the tyres	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

BERU TYRE SAFETY SYSTEM (TSS): WORKSHOP TIPS

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:

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/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 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

tire 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 tire 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).

TSS BERU: Tyre pressure monitoring system components

Fig. 1: 1 Wheel electronics, 2 Wheel electronics with tire 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

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 trunk 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 read into the system, instead of the usual four (with spare wheel five), 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.

PRACTICAL TIP

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.

Diagnostic units such as the Hella Gutmann mega macs 42 SE, 56, 66 or PC, 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.

Coding is realised as follows:

Connect the diagnostic unit to the vehicle
Call up the program coding
Read in the valve codes using the valve exciter

PRACTICAL TIP

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 profile 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.

EU LEGISLATION ON TYRE PRESSURE MONITORING SYSTEMS: GOOD TO KNOW

On March 10, 2009, the European Parliament in Strasbourg officially approved a proposed regulation (EC No. 661/2009) of the Commission to simplify the type approval of vehicles in Europe. This regulation also stipulated the mandatory introduction of technologies which are already established, including tyre pressure monitoring systems (TPMS). Vehicles of category M1 / M1G must be equipped with an accurate tyre pressure monitoring system capable of giving, when necessary, an in-car warning to the driver when a loss of pressure occurs in a tyre, and so optimum fuel consumption and road safety are no longer guaranteed. The implementation was gradual: From November 2012, all new vehicle types with type approval had to be equipped with tyre pressure monitoring systems; from November 2014, this has applied to all new registered vehicles.