TPMS Sensors – The Tyre Pressure Monitoring System for Greater Safety and Efficiency
TPMS (Tyre Pressure Monitoring System) – the tyre pressure monitoring system – has long ceased to be a luxury and is now an essential part of modern vehicle safety. Since 2012, all newly type-approved passenger cars in the EU have had to be equipped with a functioning tyre pressure monitoring system; since November 2014, the TPMS requirement has applied to all newly registered passenger cars. Indirect or direct TPMS sensors permanently monitor the air pressure in your tyres and warn early of pressure loss – this not only prevents dangerous tyre blowouts but also saves fuel and is kind to your tyres.
Regardless of the requirement, it is worth taking a look at the technology: tyre pressure that is 0.5 bar too low increases rolling resistance, drives fuel consumption up by as much as 0.3 litres per 100 km and shortens the service life of the tyre by several thousand kilometres. At the same time, the braking distance on a wet road increases noticeably. With intact TPMS sensors, you recognise deviations immediately and can act in good time.
In this guide you will learn everything you need to know about the various TPMS sensor types, their service life, correct teach-in and replacement – and how to find the right sensor for your vehicle at Electronicx.
Direct vs. indirect TPMS sensors – the differences at a glance
In principle, a distinction is made between two systems: direct TPMS with separate sensors in the wheels and the indirect system, which uses the existing wheel speed sensors. Both variants have specific advantages and disadvantages that are decisive when buying parts.
Direct TPMS sensors
Direct systems work with one sensor per wheel, mounted in the valve or on the wheel rim bed. Each sensor measures temperature and tyre inflation pressure precisely (typical accuracy: ±0.1 bar) and transmits its data by radio (mostly 433 MHz, rarely 315 MHz) to the control unit. The sensors have their own battery with a typical service life of 5 to 10 years – after that, the entire sensors must be replaced because the button cell is permanently encapsulated. Direct TPMS are highly accurate, detect pressure loss from a deviation of around 0.2 bar and often display the actual pressure of each wheel in the instrument cluster.
Indirect TPMS systems
Indirect systems use the ABS wheel speed sensors that are already present. They do not detect pressure loss directly from a measured pressure, but via the changed rolling circumference: a tyre with less air rotates faster. An algorithm compares the wheel speeds and triggers an alarm when a significant deviation occurs. The advantage: no expensive individual sensors are needed, so replacement is eliminated entirely. The disadvantage is lower accuracy – the system often only warns at a pressure drop of around 25–30 %, does not detect gradual pressure loss on all four wheels at the same time and requires manual recalibration after every tyre change or pressure adjustment (reset by pressing a button). Indirect TPMS is found mainly on older vehicles and many small cars.
| Feature | Indirect TPMS |
|---|---|
| Measuring principle | Wheel speed sensors (ABS) |
| Accuracy | Low, detects only relative deviations >25 % |
| Warning | Late, often only at a significant pressure drop |
| Sensor battery | None, as there are no separate sensors |
| Maintenance effort | Manual reset after tyre change/pressure correction |
| Approximate cost per sensor (spare part) | Not applicable (no part required) |
Most current vehicles from BMW, Mercedes, VW, Audi and other manufacturers use direct TPMS sensors. If the tyre pressure warning light on your car's display shows the specific air pressure of each wheel, it is very likely a direct system.
When do TPMS sensors need to be replaced? – Service life and typical failures
The common question is: “My sensors are only five years old – why is the warning light on despite correct tyre pressure?” The problem is almost always a depleted battery. A direct TPMS sensor contains a permanently installed lithium button cell (3 V) that cannot be replaced. The typical capacity is around 300–500 mAh, which lasts 5 to 10 years depending on the driving profile and transmission frequency. A sensor with 8 years of use is not unusual, but extreme temperatures and frequent data transmissions (e.g. on vehicles with a permanent wheel display) can shorten the service life.
How to identify a faulty or battery-less TPMS sensor
- The tyre pressure warning light flashes for 60–90 seconds after starting and then stays on continuously.
- The on-board computer shows no pressure value (“–”) for one wheel, or the value jumps between normal and 0.0 bar.
- The control unit reports “sensor fault” or “check TPMS system”.
- After a tyre change (summer/winter wheels), the vehicle no longer recognises one or all sensors – a frequent sign of a weak battery or incompatibility.
Besides the battery, mechanical damage or corrosion on the valve can also cause failure. Particularly with older aluminium valves or frequent wheel changes with aggressive fitting, microcracks can form that encourage air loss and endanger the sensor electronics. A functioning sensor can be tested with a diagnostic tool – at Electronicx you receive not only the matching replacement sensors but also troubleshooting instructions.
Buying TPMS sensors: how to find the right sensor for your vehicle
The range of tyre pressure sensors is wide – alongside manufacturer-specific OE sensors there are high-quality aftermarket alternatives that use the same protocols and are often up to 40 % cheaper. The following parameters are decisive for the selection:
- Vehicle model and year of manufacture: Each manufacturer uses specific control units and communication protocols. A BMW 3 Series (G20) requires a different sensor from a Mercedes C-Class (W205) or a VW Golf 8.
- Frequency: In Europe almost all vehicles work with 433 MHz, some imported models from the USA or Asia with 315 MHz. The frequency must match exactly.
- Valve type: There are rubber valves (standard) and metal valves (often for higher speeds or special rims). Make sure the design matches.
- Configurability: Multiprotocol universal sensors can be set to the protocol of various manufacturers and are particularly suitable for workshops that cover many brands. For the end customer, however, preconfigured, vehicle-specific sensors are preferable.
In our online shop you will find sensors for almost all common makes. Use our vehicle search or enter the OE number of your old sensor. If you are unsure, our support team will be happy to help you on +49 7135 7194106 or by email at [email protected].
Teaching in TPMS sensors – step by step
A new or repositioned TPMS sensor usually has to be "taught in" to the control unit so that it recognises the new sensor ID and assigns it correctly. The process depends on the vehicle and ranges from automatic recognition after a short drive to a multi-stage diagnostic process with a special teach-in tool. In most cases, however, it works as follows:
- Fit the new sensors in the wheel and inflate the tyres to the prescribed pressure.
- Switch on the ignition and put the vehicle into TPMS learn mode (depending on the make, via the on-board computer menu or a button combination).
- For systems with manual teach-in: use an activation tool to trigger the sensors in the order front left, front right, rear right, rear left. The vehicle usually confirms successful teach-in with a horn signal.
- For automatic systems (e.g. many models from 2016 onwards): drive for around 10–15 minutes at a speed of at least 25 km/h and the sensors register themselves automatically.
- Check whether all four pressures are shown in the instrument cluster.
For detailed instructions tailored exactly to your vehicle, visit our pages:
Installation and fitting of tyre pressure sensors
Fitting TPMS sensors is a job for a tyre specialist, because the tyres have to be removed from the rim and the sensors must be fastened with the correct tightening torque (usually between 4 and 8 Nm). Replacing the valve service kit (seal, valve core, union nut) is also advisable in order to avoid leaks.
After fitting, the sensor must be taught in as described in the previous section. Never use sensors whose battery is more than 2 years old, as they may otherwise fail before the expected remaining service life has elapsed.
Your partner for TPMS sensors – Electronicx GmbH from Cleebronn
Electronicx is a company specialising in car electronics and on-board power supply components, based in Cleebronn (Baden-Württemberg). We supply direct TPMS sensors from well-known manufacturers as well as high-quality vehicle-specific preconfigured sensors that meet the quality standards of established original equipment manufacturers.
Delivery & shipping: Within Germany we ship free of charge with DHL. The delivery time is usually 1–2 working days. We also ship to Austria, Switzerland and other countries – please ask for the shipping costs by phone or email.
Contact:
Electronicx GmbH
Hindenburgstr. 37A
74389 Cleebronn
Germany
Tel: +49 7135 7194106
Email: [email protected]
Beyond the pure TPMS range, we also offer AGM batteries for start-stop systems, chargers and much more – simply take a look around our shop.
Frequently asked questions about TPMS sensors
What does the TPMS warning light mean and how should I react correctly?
The light (often a tyre cross-section with an exclamation mark) warns of pressure loss. If it stays on continuously, the pressure of one or more tyres is at least 20 % below the specified value. If it flashes when you start driving and then stays on continuously, there is often a system fault (e.g. a defective sensor). Stop, check the tyres and correct the pressure. Do not continue driving with unchecked pressure.
Do I have to relearn new TPMS sensors after changing tyres?
When changing to another set of wheels (summer/winter tyres) with its own sensors, a relearn procedure is required in most vehicles so that the control unit adopts the new sensor IDs. On vehicles with automatic relearning, a drive of several minutes is often sufficient; on manual systems, a relearn tool is needed. You can find exact information in our guide to TPMS relearning.
How long does the battery of a direct TPMS sensor last?
The fitted 3-volt lithium button cell achieves an average service life of 5 to 10 years, depending on quality, driving profile and temperature exposure. Frequent use on motorway journeys and high ambient temperatures can reduce the service life somewhat. After about 7 years, a preventive replacement on all four wheels is advisable.
Can I fit TPMS sensors myself?
In principle yes, if you carry out the tyre fitting yourself. You need a tyre fitting machine and a torque wrench to tighten the sensor correctly. As a rule, however, fitting including relearning is left to a tyre specialist, as mistakes can lead to leaks and sensor failures.
Are indirect TPMS systems just as safe as direct ones?
Indirect systems detect pressure loss less promptly and not in all scenarios (e.g. uniform pressure loss on all four wheels). Direct sensors provide precise actual values and warn considerably earlier – they therefore offer a higher level of safety. Nevertheless, both systems meet the legal requirements.
How do I know which TPMS sensor fits my vehicle?
The easiest way to search is by vehicle identification (make, model, year of manufacture) or by the OE reference number of your old sensor. Detailed filters help you in our online shop. If you have any questions, you can reach us at [email protected] or by telephone.
Does Electronicx offer shipping to Switzerland or Austria?
Yes, on request we also deliver to Austria and Switzerland. Shipping within Germany is free for you (DHL). For deliveries to other countries, additional shipping charges apply; please ask us for these.
Why does the TPMS lamp light up despite correct air pressure?
This indicates either a faulty sensor (flat battery, mechanical damage) or a system fault. An unlearned spare wheel or a signal suppressed by radio interference can also be the cause. A diagnosis with a TPMS tester provides clarity.