TPMS sensors – the tyre pressure monitoring system for more safety and efficiency
TPMS (Tire 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 2014, all newly type-approved passenger cars in the EU have had to be equipped with a functioning tyre pressure monitoring system; since November 2016, the TPMS requirement has applied to all new vehicles. 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 kinder to your tyres.
Regardless of the requirement, it is worth looking 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 tyre's service life 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 relearning and replacement – and how to find the right sensor for your vehicle at Electronicx.
Direct vs. indirect TPMS sensors – the differences at a glance
There are basically two systems: direct TPMS with dedicated sensors in the wheels and the indirect system, which relies on 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. Each sensor measures temperature and tyre 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 sealed in. Direct TPMS are highly accurate, detect pressure loss from a deviation of around 0.2 bar and often show the actual pressure of each wheel in the instrument cluster. However, depending on the vehicle model, the sensors cost between €25 and €120 each and require a certain amount of care during a tyre change so that they are not damaged.
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, and replacement is not required at all. The disadvantage is the 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 are found mainly on older vehicles and many small cars.
| Feature | Direct TPMS | Indirect TPMS |
|---|---|---|
| Measuring principle | Pressure and temperature sensor in the wheel | Wheel speed sensors (ABS) |
| Accuracy | High, approx. ±0.1 bar, shows absolute values | Low, detects only relative deviations >25% |
| Warning | Early, even at low pressure loss | Late, often only at significant pressure drop |
| Sensor battery | Yes, the service life depends on use, charging, temperature and care, then replacement | None, as there are no separate sensors |
| Maintenance effort | Sensor replacement when the battery ends, otherwise maintenance-free | Manual reset after tyre change/pressure correction |
| Approximate cost per sensor (spare part) | €25–120 (depending on model) | Not applicable (no part needed) |
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 frequent question is: “My sensors are only five years old – why is the warning light on despite correct tyre pressure?” The problem is almost always an exhausted 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 radar display) can shorten the service life.
How to recognise a defective 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 of the 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 with frequent wheel changes involving aggressive fitting, microcracks can form that encourage air loss and put the sensor electronics at risk. A functioning sensor can be tested with a diagnostic tool – at Electronicx you not only get the right replacement sensors, but also guides for fault diagnosis.
Buy 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 choice:
- Vehicle model and year of manufacture: Every manufacturer uses specific control units and communication protocols. A BMW 3 Series (G20) needs 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 is the right one.
- 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 on +49 7135 7194106 or by email at [email protected].
Learning TPMS sensors – step by step
A new or repositioned TPMS sensor usually has to be “learned” by 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 learning 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 learning mode (depending on the make, via the on-board computer menu or a button combination).
- For systems with manual learning: use an activation tool to trigger the sensors in the order front left, front right, rear right, rear left. The vehicle usually confirms successful learning with a horn signal.
- For automatic systems (e.g. many models from 2016 onwards): drive for about 10–15 minutes at at least 25 km/h and the sensors register themselves.
- 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 have to 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. The cost of fitting and programming at an independent workshop is typically 20–40 € per wheel, depending on the type of rim and the vehicle.
After fitting, the sensor must be learned as described in the previous section. Never use sensors whose battery is older than 2 years, as they may otherwise fail before the expected remaining life has elapsed.
Your partner for TPMS sensors – Electronicx GmbH from Cleebronn
Electronicx is a company specialising in car electronics and electrical system components, based in Cleebronn (Baden-Württemberg). Here you will find direct TPMS sensors from well-known manufacturers as well as vehicle-specifically pre-programmed sensors that meet the quality standards of established original equipment manufacturers.
Delivery & shipping: Within Germany, shipping is free with DHL. The delivery time is usually 1–2 working days. We also ship to Austria, Switzerland and other countries – please ask us for the shipping costs by telephone or email.
Contact:
Electronicx GmbH
Hindenburgstr. 37A
74389 Cleebronn
Germany
Tel: +49 7135 7194106
Email: [email protected]
Beyond the pure TPMS range, you will also find 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?
The light (often a tyre cross-section with an exclamation mark) warns of pressure loss. If it is permanently lit, 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 lit, 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 switching to a different set of wheels (summer/winter tyres) with their own sensors, a relearning procedure is required in most vehicles so that the control unit adopts the new sensor IDs. In vehicles with automatic relearning, a drive of several minutes is often enough; with manual systems, a relearning tool is required. You can find exact information in our guide to TPMS relearning.
How long does the battery of a direct TPMS sensor last?
The built-in 3‑volt lithium button cell achieves an average service life of 5 to 10 years, depending on quality, driving profile and temperature load. 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 changing machine and a torque wrench to tighten the sensor correctly. As a rule, however, fitting and relearning are 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 early and not in all scenarios (e.g. uniform pressure loss on all four wheels). Direct sensors provide precise actual values and warn significantly 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). Deliveries to other countries incur additional shipping charges, which you are welcome to ask us about.
Why is the TPMS light on despite correct tyre pressure?
This indicates either a defective 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.