TPMS sensor relearn: instructions for many vehicle makes

What is TPMS sensor relearning? Basics

Relearning a TPMS sensor describes the process in which the unique sensor ID is registered in the vehicle's control unit. Without this process, the tyre pressure monitoring system does not recognise the new sensors – the TPMS warning light flashes and the system remains inactive. Every direct TPMS sensor transmits its ID as well as pressure and temperature values to the receiving module in Europe at 433.92 MHz.

Sensor ID and radio communication

Every wheel sensor has a hexadecimal 32-bit ID identifier that is permanently programmed at the factory. When new sensors are fitted, the control unit must learn these IDs. Modern sensors use protocols such as Schrader, Siemens VDO, Pacific or Huf/Beru – each with specific telegram structures and CRC checksums. Transmission uses FSK or ASK modulation with a transmission power of no more than 10 mW in order to avoid interference with other radio services.

Auto-learn vs. stationary learn

With auto-learn, the vehicle registers new sensors by itself while driving. The control unit detects unknown IDs, compares the signal strength of the four wheel positions and assigns them automatically. This method is used above all by Opel, Ford and older Toyota models. With stationary learn, an OBD tool must write the IDs manually into the control unit. VAG, BMW and Mercedes mainly use this method, in which the vehicle is put into a learn mode.

Trigger procedure in detail

Stationary learn requires each sensor to be triggered with a low-frequency signal (125 kHz), which wakes the sensor and forces it to transmit data immediately. Without a trigger, the sensor waits for up to 60 seconds when stationary for the next transmission interval. Professional tools such as the Autel TS508 or ATEQ VT56 combine OBD communication with integrated trigger functions and thus cover over 98 % of all direct TPMS. Under ECE Regulation 64, all passenger cars newly type-approved from 1 November 2014 must have a functioning TPMS – relearning is therefore not an option but a requirement.

Why do TPMS sensors have to be relearned?

TPMS sensors always have to be relearned when the stored sensor IDs in the control unit change. This happens with every wheel change involving new sensors, when changing from summer to winter tyres with their own set of wheels, or when a sensor fails because of an empty battery. A TPMS that has not been relearned leads to a permanent warning light in the instrument cluster.

Scenario 1: faulty sensor and battery service life

The lithium button cell of a TPMS sensor typically lasts 5–10 years, depending on the driving profile. The battery is permanently encapsulated and cannot be replaced – a voltage drop below 2.1 V leads to failure. After replacing the sensor, the new ID must be relearned, as otherwise the control unit continues to look for the old ID, which is no longer transmitting, and sets the fault code “sensor not found”.

Scenario 2: complete wheel change with a separate TPMS set

Many vehicle owners use two sets of wheels – one for summer, one for winter. If both sets are fitted with sensors, the current set of wheels must be relearned at every seasonal change. Some manufacturers such as BMW (from model year 2014) store two sets of wheels in parallel, but most vehicles can only manage one set of IDs at a time. Manual relearning via the instrument cluster only works on a few models (e.g. Toyota RAV4); on most, an OBD tool is required.

Fault codes and their meaning

If a sensor is not taught in, manufacturer-specific fault codes appear in the TPMS control unit. Common codes are C1100–C119F (sensor ID missing), U0126 (loss of communication) or B2872 (pressure too low). Reading out via an OBD tool shows exactly which sensor is not recognised at which position. Especially when the vehicle is loaded or on long motorway journeys at speeds above 160 km/h, a calibrated system is essential.

Differences between direct and indirect TPMS

The fundamental distinction in the tyre pressure monitoring system concerns the measuring method. Direct TPMS physically measures pressure and temperature inside the tyre; indirect TPMS calculates pressure losses from the wheel speed signals of the ABS. Only direct TPMS requires sensors to be taught in – and this is precisely the system fitted in most European vehicles from model year 2014 onwards.

Direct TPMS: design and function

Each wheel sensor contains a piezoresistive pressure sensor, a temperature sensor, a microcontroller with an ID-32-bit identifier, a transmitting antenna and a lithium battery with 3.0 V nominal voltage. The sensor measures the tyre pressure in the range from 1.8 bar to 3.5 bar with an accuracy of ±0.07 bar and sends a data packet every 30 to 120 seconds. When stationary, the sensor goes into sleep mode to save battery. Vehicles with direct TPMS display the pressure for each wheel in the instrument cluster – often with specific bar values.

Indirect TPMS: ABS-based pressure monitoring

Indirect systems require no sensors in the tyre at all. They use the ABS wheel speed sensors and detect pressure losses via the changed rolling geometry: a tyre with lower pressure has a smaller rolling circumference and rotates faster. The software detects differences from a pressure loss of 0.3 bar, but cannot detect gradual losses on all four tyres. Indirect TPMS must be initialised via the instrument cluster – a five-second button press on the TPMS button starts the calibration process, which requires about 20 km of driving. Teaching in with an OBD tool is not required at all.

Which system requires teaching in?

Teaching in sensors is necessary only with direct TPMS. Owners of vehicles with indirect TPMS can ignore this point entirely – after a wheel change they only need to carry out the initialisation via the vehicle menu or the reset button. ECE Regulation 64 has required a functioning TPMS for all new passenger car type approvals since November 2014, but permits both system variants. In practice, European manufacturers use direct systems in over 90 % of cases, because only these can display the pressure precisely and for each wheel.

Requirements for teaching in: tool and compatibility

Successfully teaching in a TPMS sensor requires three things: a compatible diagnostic tool, knowledge of the manufacturer-specific teaching procedure and the correct sensor IDs. Without an OBD tool, teaching in is not possible on most vehicles from model year 2014 onwards. We show the most important professional tools and explain the differences between the manufacturer protocols.

Professional OBD tools in comparison

The market is dominated by two devices: the Autel TS508 and the ATEQ VT56. The Autel TS508 supports over 98 % of all direct TPMS with OBD connection and can read out, program and relearn sensor IDs. Its 3.5-inch colour display shows pressure and temperature live. The ATEQ VT56 additionally offers an even more extensive vehicle database and a faster trigger function. Both devices are updated regularly via USB and cover the protocols of all European, Asian and American manufacturers. For the workshop they are indispensable; for the ambitious hobby mechanic the Autel TS508 already pays for itself by the second wheel set change.

Manufacturer-specific relearn procedures and protocols

Each manufacturer uses its own protocols and learning strategies, which makes relearning difficult without a suitable tool:

• VAG (Audi/VW/Skoda/Seat): Stationary learn via OBD. The sensors (mostly Huf/Beru) must be triggered at 125 kHz. The system expects a fixed sequence: front left, front right, rear right, rear left.
• BMW: From the F series, storage of two wheel sets is possible. Relearn via OBD with trigger in the same sequence as VAG. Sensors mostly from Schrader or Continental at 433 MHz.
• Mercedes: Stationary learn with OBD. Typical sensors from Schrader. The TPMS control unit is usually located in the boot, the OBD communication runs via the central gateway.

• Opel: Auto learn while driving. New sensors are detected automatically after 10–20 km of driving. No OBD tool required, provided original sensors or compatible types with the correct Schrader protocol are used.
• Ford: Mostly auto learn, on newer models (from 2018) also stationary learn with OBD. Frequency 433 MHz with Motorcraft protocol.
• Peugeot/Citroen: Mixed system. Some models auto learn, others require OBD. Sensors from Siemens VDO with a specific PSA protocol.

• Renault: Predominantly OBD relearn with 433 MHz Schrader sensors. Trigger sequence as VAG.
• Toyota: In Europe 433 MHz. Many models with auto learn, some require OBD. Manual relearn via the instrument cluster is possible on the RAV4 and Camry.

Compatibility check before purchase

Not every sensor fits every vehicle. Before purchase, the frequency (in Europe 433 MHz), protocol and valve type (aluminium/rubber) must be matched. The KBA database lists the approved sensor types for each vehicle. An ATEQ VT56 or Autel TS508 indicates before programming whether the selected sensor is compatible and performs the plausibility check automatically.

Step by step: relearning TPMS with an OBD tool

Relearning with an OBD tool is the safest way to register new TPMS sensors. The process follows a standardised sequence, but varies depending on the tool and vehicle. We show the complete workflow for the Autel TS508 and ATEQ VT56 – two devices that together cover over 95 % of all vehicles.

Basic preparation

Before the OBD tool is connected, all four tyres must be fitted with the new sensors and inflated to the specified pressure (usually 2.2 to 2.8 bar). The vehicle is on a level surface, the ignition is switched on, the engine remains off. On most models the OBD port is located on the left below the steering wheel. Important: during the relearn process, all radio sources in the vicinity (Bluetooth, WLAN, garage door openers) must be deactivated, as they can interfere with the 125 kHz trigger frequency.

Relearn with the Autel TS508

The Autel TS508 guides you through a menu-driven process. In the main menu, the vehicle is selected by make, model and year of manufacture. Then the menu item “Sensor relearn” → “OBD relearn”. The device communicates briefly with the TPMS control unit and then prompts you to trigger the sensors. The sequence is strict: front left → front right → rear right → rear left. The integrated trigger is held directly against the tyre sidewall close to the valve. A successful trigger is confirmed by a beep and the display of the sensor ID. Once all four IDs have been recorded, the TS508 writes the data to the control unit via OBD. After a brief plausibility check, the tool displays “Relearn successful”. A subsequent test drive of 5 kilometres ensures that all sensors are detected correctly.

Relearn with the ATEQ VT56

The VT56 works on the same principle, but offers even faster trigger detection and a larger vehicle database. After vehicle selection, the VT56 starts the relearn mode. Here too, triggering takes place in the sequence starting with front left. The VT56 stores the IDs and compares them with the internal database for protocol compliance. The OBD write command is then executed. A notable advantage of the ATEQ VT56: on BMW vehicles from model year 2014, it can select the second wheel set directly and store it separately – without overwriting the first. After a successful write, ATEQ recommends restarting the ignition and a 10-minute test drive at speeds above 25 km/h so that the control unit can clearly assign the sensor positions.

Plausibility check and validation

After the relearn process, a plausibility drive is mandatory. The TPMS control unit compares the signal strengths of the individual IDs and definitively assigns them to the wheel positions. Most vehicles require 10–20 minutes of driving for this. During this time the system cannot display pressure warnings – the lamp only goes out after successful position assignment. A final check with the OBD tool shows whether all four IDs are assigned to the correct positions and the pressure values are plausible (±0.1 bar tolerance). Only then is the TPMS fully functional and does it meet the legal requirements of ECE R64.

6. Relearning TPMS without tools: is that possible?

6.1 Auto-learn vs. stationary learn

Whether a TPMS teach-in is possible without a special diagnostic tool depends on the vehicle system used and the sensor protocol. In principle, a distinction is made between two methods: with auto-learn, after a wheel or sensor change the vehicle drives a certain distance and the control unit detects the new sensor IDs itself via the radio signals. This method is common, for example, with some Asian manufacturers. The prerequisite is a defined driving cycle: at least 15 minutes of uninterrupted driving at over 25 km/h so that the sensors wake from sleep mode and transmit their IDs.

By contrast, stationary learn requires the manual or tool-assisted entry of the sensor IDs with the vehicle stationary. European manufacturers such as VAG, BMW and Mercedes almost consistently use this method, as it prevents theft and incorrect assignment with multiple wheel sets. A pure auto-learn mode is the exception here.

6.2 Limits of manual teach-in without an OBD tool

Without a tool, a stationary learn is only possible on a few vehicles via the on-board menu, and even then the control unit often first has to be enabled for learn mode via a diagnostic device. Since 2014, ECE Regulation 64 has required a direct TPMS for new cars in the EU, which as a rule uses coded sensors with a 433 MHz frequency. In addition to pressure and temperature values, these sensors also transmit the individual, permanently assigned 8-digit ID, which must be stored in the TPMS control unit.

Typical fault codes such as C1102 (sensor ID not recognised) or 01325 (no signal from the tyre pressure monitoring module) show that a complete learn procedure is not possible without write access via the OBD interface. Nevertheless, there are vehicles, such as the third-generation Ford Focus, on which a manual training mode via the hazard warning button and a magnet can reactivate old sensors – for new sensors, however, OBD access remains essential.

Auto-learn

Vehicle independently detects new TPMS sensor IDs after a defined driving cycle (>15 min, >25 km/h) without manual intervention.

Stationary learn

Teach-in procedure with the vehicle stationary, in which sensor IDs must be programmed via an OBD tool, trigger device or on-board menu. Standard on European 433 MHz systems.

Conclusion: A genuine teach-in completely without a tool fails on 9 out of 10 European vehicles due to the obligatory ID programming. To be on the safe side, at least a TPMS trigger device is required in conjunction with the vehicle's own learn routine – and for coded systems an OBD diagnostic tool such as the Autel MaxiTPMS TS508 or the ATEQ VT56 is essential.

7. Specific instructions for VW (Golf, Passat, Tiguan)

7.1 Platform overview and system variants

All Volkswagen Group vehicles on the modular transverse matrix platform (MQB) – including the Golf VII/VIII, Passat B8, Tiguan II, Skoda Octavia, Seat Leon – use a direct TPMS with a 433 MHz frequency and coded sensors. The sensor IDs are stored in control unit J502 (address 65). In contrast to earlier indirect systems via ABS sensors, an electronic identification comparison is mandatory here. The system distinguishes up to 4 wheel sets (summer, winter, spare), which makes the ID change necessary when wheels are swapped.

7.2 Step-by-step learn routine with diagnostic tool

1. Ignition on, engine OFF. Connect the OBD diagnostic device (e.g. Autel TS508) and select the vehicle type.
2. Select the menu item Tyre pressure monitoring → Program sensor.
3. Read out the existing sensor IDs and overwrite them with new IDs or start “relearn all sensors”.
4. Activate each wheel one after the other with the trigger device (LF trigger 125 kHz) until the control unit acknowledges the ID. Sequence: front left → front right → rear right → rear left.
5. After successful programming, clear the fault memory and carry out a short test drive (> 5 minutes above 25 km/h) so that the sensors transmit continuously and no new fault code is generated.

Practical example: An Audi A3 8V with start-stop automatic transmission and AGM battery shows the message “Check tyre pressure – system fault” after a wheel change. Here only reading in the four new sensor IDs with the TS508 helps, as the TPMS control unit reacts particularly sensitively to implausible pressure values after a voltage drop caused by the start-stop automatic system and sets fault code 02433.

7.3 Finding the right sensor

Which sensor fits depends on the model and year of manufacture. VW models in Europe use 433 MHz. You can find the right sensor in the TPMS assistant by vehicle or HSN/TSN; the OE number on the old sensor helps with the comparison.

8. TPMS relearn on BMW (3 Series, 5 Series, X3)

8.1 System architecture and RDC function

Since the introduction of tyre pressure control (RDC), BMW has used a proprietary 433 MHz protocol that communicates via the RDC antenna (usually in the wheel arch or underbody). On vehicles from model year 2010 (E90 LCI, F30, G20, G30, F25 X3), coded sensors with a fixed 8-digit ID are installed. The RDC control unit (function code 2VB) continuously compares pressure, temperature and acceleration values. A special feature is the sleep-wake mechanism: BMW sensors switch to a sleep mode with a current consumption of only 0.1 µA after standstill and are reactivated by centrifugal force (from approx. 25 km/h) and an LF signal.

8.2 Manual relearn via iDrive and workshop tool

On a limited number of BMW vehicles (e.g. F30 3 Series before the 2015 facelift), a wheel change can be acknowledged via the iDrive menu Vehicle → Tyre pressure → RDC reset – the control unit then searches for new IDs in auto-learn mode. However, this only works if the sensors are already known to the system. After a sensor change, the new IDs must be written in via an OBD tool. Diagnosis is carried out via the CAN bus (K-CAN2) and address B7.

With the Autel TS508, after selecting the vehicle (BMW → 3 Series → F30), the existing ID list is read out and overwritten with the newly activated IDs. The programming process typically takes 5–10 minutes. Fault codes such as 481B02 (sensor timeout) or 481B01 (no reception) indicate that the old ID is still stored or the sensor is not transmitting.

8.3 Table: BMW vs. competitor relearn procedures

BMW owners should note that the RDC sensors have a battery that typically lasts 5–10 years. After a voltage drop below 2.1 V (with a nominal 3.0 V lithium cell), the sensor suspends the transmission interval and is registered as defective.

9. Mercedes TPMS relearn (A-Class, C-Class, E-Class)

9.1 RDK systems and protocol variants

Mercedes-Benz fits direct tyre pressure monitoring systems in the compact A-Class (W176, W177), the C-Class (W205, W206) and the E-Class (W213), which transmit on 433 MHz depending on the market in Europe. The control unit is integrated into the NTG infotainment system (e.g. NTG5.2, NTG6) and communicates with the wheel sensors via CAN-C. Each sensor transmits a 6-byte ID as well as pressure (accuracy ±0.07 bar) and temperature values. From the factory the sensors are coded and must comply with the KBA database (ECE Regulation 64-02).

9.2 Stationary learn with ATEQ VT56 and steering wheel menu

On many Mercedes models a manual ID matching is prepared via the on-board menu in the instrument cluster (Service → Tyre pressure → Teach in sensors) – but without activation by a diagnostic device the communication usually fails. The procedure with an ATEQ VT56:

1. Connect the ATEQ VT56 to the OBD port and have the vehicle identification read automatically (VIN parsing).
2. Select TPMS → ID programming → Mercedes-Benz.
3. Trigger each wheel one after the other with the integrated LF trigger device (125 kHz) within 30 seconds per position – the order is FL, FR, RR, RL.
4. Write the new IDs into the TPMS control unit via OBD, confirm the memory, ignition OFF and ON.
5. After a successful test drive, delete fault codes such as C110200 (signal from a tyre pressure sensor missing) or C110100 (pressure loss warning).

The A-Class W177 in particular reacts sensitively to missing sensor acknowledgements and after 20 minutes without ID reception no longer deactivates the TPMS warning light by itself – so using a tool is essential here.

9.3 Sensors for the winter wheel set and battery

For a second wheel set, a direct system needs its own sensors. The battery of a sensor typically lasts 5–10 years and is permanently installed; when it is empty, the sensor is replaced. More on this: TPMS sensors for winter wheels.

10. Teaching in Ford TPMS (Focus, Mondeo, Kuga)

10.1 Training mode without a diagnostic device? Options and limits

On many models – in particular the Focus (MK3/MK4), Mondeo (MK5) and Kuga (MK2/MK3) – Ford offers a manual training mode that at first glance allows new sensors to be taught in without an OBD tool. The procedure: ignition ON, press the hazard warning button 3 times, the horn sounds once. The sensors must then be activated one after the other with a TPMS trigger device (125 kHz LF signal) or – with older sensors – with a strong permanent magnet (field strength > 50 mT) in the order FL, FR, RR, RL. Successful reception is acknowledged by a short horn signal.

However, this method only works with original sensor IDs already stored in the system. If new aftermarket sensors have been fitted whose IDs are not stored in the control unit, the learn procedure aborts with the flashing code 4 flashes of the warning light. In this case an OBD diagnostic device must be connected.

10.2 OBD programming with Autel TS508

The procedure with an Autel MaxiTPMS TS508 is particularly efficient on Ford vehicles, as via the OBD interface the device not only programs the IDs but also automatically detects the sensor positions and re-parameterises the Body Control Module (BCM):

1. Connect the Autel TS508 to the OBD port (often under the steering wheel on the left), have the vehicle identified via VIN.
2. Programming → Teach in new sensors → Ford → Focus 2019. Display the existing ID table.
3. Activate the sensors one after the other with the LF trigger. The TS508 immediately shows pressure, temperature and ID.
4. After acknowledging all four positions, the new IDs are written to the BCM via the CAN protocol (11-bit identifier, 500 kbit/s). The process takes about 3–4 minutes.
5. Test drive of at least 15 minutes above 30 km/h – the system checks the plausibility range (pressure 1.5–3.5 bar, temperature -20 °C to +60 °C) and clears the warning lamp.

10.3 Frequency: 433 MHz in Europe

European Ford models use 433 MHz. Vehicles for other markets (e.g. US imports) may use a different frequency; a 433 MHz receiver does not detect such sensors. Before buying a sensor, it is necessary to look at the old valve or the control unit label. The Kuga MK3 (from 2020) already uses an extended protocol version with +10 dBm higher transmission power and cyclic data intervals of 30 seconds (normally 60 seconds), which enables the tyre position to be located after less than 2 minutes of driving.

TPMS relearn on Opel, Audi, Skoda (VAG Group)

VAG platform: Audi, VW, Seat, Škoda – direct system with VCDS/OBDII

All vehicles of the Volkswagen Group (VW AG) from model year 2014 onwards use a direct TPMS with wheel sensors that transmit on 433 MHz (Europe). The control unit (usually address 65) expects the programmed sensor IDs in a fixed order: front left – front right – rear right – rear left. On Audi A3 8V, A4 B9, Q5 FY or VW Golf VII/VIII, the write process is carried out via OBD-II. With the VW software VCDS (from HEX-V2) or ODIS, you write the 7- or 8-digit HEX IDs (e.g. 0x7A3F1C2) directly into the memory of the comfort control unit. Alternatively, diagnostic devices such as Autel TS508 or ATEQ VT56 instruct the control unit via OBD command to read in the newly detected sensor IDs (“OBD Relearn”). Important: On MQB Evo platforms (Golf VIII, Leon IV) from 2021, access to address 65 is SFD-protected – without online activation (GeKo/SVM), only the workshop route remains.

Opel: from Auto-Learn to EL-50448

Depending on the model generation, Opel uses different procedures. Vehicles of the GM era (Insignia A, Astra J, Corsa D, Mokka A) often work with a self-learning procedure (Auto-Learn). After correctly inflating the tyres and a drive above 25 km/h, the control unit automatically detects the new sensor IDs and assigns them to the positions. Only the correct reference pressure is required for this. Newer models from 2018 (Insignia B, Corsa F, Mokka B) on the PSA platform require a Stationary Learn – the sensor must be activated individually while stationary with an LF trigger (125 kHz). The low-cost programming trigger EL-50448 proves useful here. After triggering, an OBD tool writes the detected IDs into the control unit. Important: Always check the OE reference on the old sensor before buying replacement sensors.

Frequencies and protocols in the VAG/Opel world

European VAG vehicles transmit exclusively on 433.05–434.79 MHz in accordance with ETSI EN 300 220. Vehicles for the US market may use a different frequency – an import from the USA therefore frequently has to be converted. Sensor communication follows the UHF protocol with FSK or ASK modulation. During OBD programming, the tool sends the so-called Mode $28 (FF FF) to trigger the relearn mode, followed by the four sensor IDs in HEX order. Modern tools such as the ATEQ VT56 support automatic protocol matching and thus avoid collisions with the immobiliser.

Asian manufacturers: Toyota, Honda, Hyundai

Toyota: auto-learn and manual triggering

Toyota relies almost consistently on an auto-learn function for its direct TPMS systems (e.g. RAV4, Corolla from 2017). After fitting new sensors, an initialisation drive of about 10–15 minutes at a constant 40 km/h is sufficient. The control unit identifies the four strongest sensor signals (EU models 433 MHz) and assigns them to the wheel positions via the RSSI value. A separate OBD write process is not required. It only becomes critical if you change complete wheels with sensors that were already programmed with a different ID on another Toyota – in that case, briefly pressing the TPMS reset button under the steering wheel (often near the glovebox) for 3 seconds helps, until the warning light flashes three times.

Honda: sensor ID via OBD or self-learning

Honda (Civic X, CR-V, HR-V) requires an OBD relearn on most models built from 2016. The control unit (body control module) requires the hexadecimal ID of each sensor in the order of the installation position. With the Autel TS508, the IDs can be read out and transferred directly to the vehicle in “OBD Write” mode – typically for Honda without manual LF triggering, as the tool requests the position input when connected to the OBD socket and the sensor in the wheel remains in “sleep” mode – only after successful writing does the control unit wake it with a 125 kHz wake-up call. Older Honda models (Civic IX) had an indirect system without sensors – in that case no relearn is necessary, only a reset button.

Hyundai/Kia: stationary learn with pressure change

Hyundai and Kia (i30, Tucson, Sportage) from 2018 use a stationary learn via LF trigger. The sensor must be woken from its storage state with the OBD tool or an LF trigger (125 kHz). The decisive difference: some models require a pressure change during the relearn process. You must release at least 0.3 bar from the tyre pressure on the fitted wheel within 30 seconds so that the control unit recognises the new ID as “active”. If the pressure remains constant, the system refuses to accept it. The use of the ATEQ VT56 with guided Hyundai protocol, which prompts step by step to release air, is therefore recommended.

Relearning the TPMS sensor ID: technical background

What is the sensor ID and why is it unique?

Every direct TPMS sensor carries a globally unique 32-bit identification number from the factory (abbreviated: sensor ID), represented as a 7- or 8-digit hexadecimal number (e.g. 3F A7 2C 1D) – that corresponds to over 4.2 billion possible combinations. This ID is permanently stored in the sensor's EEPROM and is transmitted with every data transmission (together with pressure, temperature and battery status) in the 433 MHz telegram. The control unit maintains a whitelist of the four expected IDs. Only if the received ID matches the learned one is the pressure displayed on the instrument cluster – an essential safety mechanism that prevents cross-interference from other vehicles in dense city traffic.

Protocols: FS code, HEX, decimal – communication with the control unit

In the world of diagnostics, three common formats exist: the FS code (Factory Serial) is the raw value assigned by the sensor manufacturer (e.g. Schrader, Huf, Continental). The HEX format is the direct representation for OBD transmission (8 characters, hexadecimal). Some Asian manufacturers expect a decimal ID (ten digits). Modern tools such as the ATEQ VT56 translate automatically between the three formats. At the VAG group, the Mode $28 command is sent in hexadecimal: 28 FF FF for "relearn all sensors". The control unit responds with a positive acknowledgement (ACK) when the IDs have been received in the correct order.

How data transmission works via LF trigger (125 kHz) and UHF (433 MHz)

A sensor in storage state transmits only sporadically in order to conserve the 3 V lithium battery. Only an LF wake-up call at exactly 125 kHz (trigger device close to the valve) activates the sensor immediately, after which it emits a UHF telegram every 0.3 seconds for around 30 seconds. The diagnostic device picks up this telegram, extracts the ID, the measured pressure (accurate to 0.1 bar) and the temperature, and then offers this data record to the OBD write process. High-quality sensors of the latest generation (Huf IntelliSens 5, Schrader EZ-sensor 2.0) also support Bluetooth Low Energy as a programming interface, so that the smartphone acts as the trigger – LF hardware is not required.

Sensor ID

32-bit globally unique identifier of the TPMS sensor (HEX: e.g. 0x3FA72C1D)

OBD-II

On-board diagnostic interface (ISO 15765-4) for writing the sensor IDs to the control unit

LF trigger (125 kHz)

Low-frequency wake-up signal that brings the sensor out of sleep mode (range approx. 10 cm)

UHF telegram

433 MHz radio telegram with pressure, temperature, ID and battery voltage

FS code

Factory Serial Number – manufacturer-specific raw ID (often longer than the HEX ID)

Mode $28

OBD command according to ISO 14229 that starts the relearn mode in the TPMS control unit

RSSI

Signal strength indicator with which auto-learn systems roughly determine the wheel position

CWA value

Cyclic Word Check – safeguard against corruption of the UHF telegram

EEPROM

Non-volatile memory in the sensor; retains ID and configuration even without a battery

ACK/NAK

Positive (acknowledgement) or negative acknowledgement from the control unit after an OBD write command

ETSI EN 300 220

European standard for short range devices; defines transmission power and channel spacing 433.05–434.79 MHz

SFD

Vehicle diagnostic protection – VAG security mechanism from MQB-Evo (GeKo activation)

Common errors and problems during relearning

Wrong sensor ID programmed – causes and remedy

The classic case: the sensor was set up with the wrong OE reference, and although the ID is recognised by the diagnostic device, the control unit rejects it. Example: a Huf IntelliSens coded for BMW transmits a telegram in the wrong protocol format. Remedy: reprogram the sensor with the correct FS code for your vehicle make (using Autel TS508 or ATEQ VT56) or – if the sensor is already mounted on the rim – replace it completely. Always check the valid OE number on the old sensor (e.g. Schrader 29148 for VAG MQB).

Sensor not recognised: LF signal too weak or frequency incompatible

If the LF trigger is held at the wrong angle or too far from the valve (> 10 cm), the sensor remains silent. Sensors with the wrong frequency are particularly tricky – the trigger does wake them, but the UHF receiver is on the wrong frequency. Solution: use a sensor with the exact frequency that the vehicle had fitted at the factory (check the sticker in the door pillar). With steel rims or armoured valves, the trigger distance can even be less than 5 cm – an extension piece for inductive triggers helps here.

Interpreting fault codes: C1073, C1074, C1075 and their meaning

The manufacturer-independent fault codes according to ISO 14229 give exact indications. A list of the most common:

• C1073 – TPMS sensor battery voltage low (below 2.1 V). The sensor must be replaced. The battery typically lasts 5–10 years.
• C1074 – Sensor ID not stored in the control unit. Carry out a new teach-in after changing tyres.
• C1075 – Signal loss / timeout. Sensor no longer transmits. The cause is often mechanical breakage after fitting.
• C1076 – Incorrect wheel position detected. Force a relearn after rotation.

TPMS after changing tyres: do I always have to teach in?

If the warning light comes on after changing tyres, you will find the most common causes step by step here: TPMS warning light after changing tyres.

Complete winter wheel sets with their own sensors

Anyone using a second wheel set with sensors already programmed and fitted must teach in again every time – unless the vehicle supports auto-learn (e.g. Toyota, older Opel models). On VAG and BMW models the OBD write process is unavoidable, because the control unit uniquely identifies each sensor by its ID. Invest in a personal tool such as the Autel TS508, and the twice-yearly workshop visit pays for itself within two seasons.

Only tyres changed, rim and sensor stay – no new teach-in needed?

Yes, correct. If only the tyre is changed and the sensor stays on the same rim at the same position, the teach-in process is not required. The control unit stores the ID-to-position assignment permanently. Note: However, some fitting shops inadvertently damage the sensor when pressing off the old tyre, so that error C1075 suddenly appears after fitting. Have the tyre service confirm in writing that all sensors are intact.

Sensor position after wheel change (rotation) – reassignment by relearn

If the wheels are swapped diagonally (front left to rear right), the TPMS control unit must learn the new positions. Without a relearn, the instrument cluster shows the pressure from front left physically at the rear right wheel – dangerous in the event of a pressure loss warning! Systems with auto-localisation (e.g. BMW via three LF antennas, VAG MQB evo) detect the new position automatically within 2–5 km of driving. Older systems, by contrast, require the manual OBD relearn, in which the sensors must be taught in in the correct order.

Cost of teaching in TPMS: workshop vs. doing it yourself

Workshop prices by vehicle make

Typical costs apply depending on the make.

Hidden costs: wrong sensors, adapters, subscription models

Allow for the following: in addition to the sensor price, fitting and teach-in may apply. Anyone who does not renew their ATEQ subscription loses access to new vehicle protocols and is left stranded with the next model year. The SFD activation at VAG (GeKo) can also be rented as a one-off 24-hour subscription – a worthwhile option for DIY mechanics.

FAQ: common questions about teaching in TPMS sensors

Conclusion and recommendations

When should you carry out the relearn yourself and when should you go to a workshop?

For all vehicles with standard OBD relearn (VAG up to 2020, Ford, Opel-PSA, BMW up to G-Series), self-help with a mid-range tool such as the Autel TS508 is worthwhile. In the long term, you save costs and are independent of workshop appointments. As soon as SFD-protected platforms (VAG from 2021), Mercedes-Benz (Xentry) or BMW with the new Secure Gateway architecture (from 2023) are involved, the workshop route often remains the only option – unless you invest in a professional tool with online connection (e.g. ATEQ VT56 with subscription). Pure auto-learn systems (Toyota, older Honda) do not require any additional equipment anyway – the on-board reset is sufficient here.

Future: Will TPMS become even easier?

Yes. The next generation – Bluetooth-based TPMS sensors (BLE 5.0, e.g. from Huf) – promises to replace LF trigger hardware. The smartphone serves as the programming interface, and the cloud stores the sensor IDs in a vehicle profile. The first manufacturers (Tesla via OTA, VW ID. series) already rely on software-defined TPMS integration, in which the gateway automatically detects and validates new sensors. By 2028, the classic OBD write process will be omitted for many new cars – for the existing fleet, however, today's knowledge remains essential. Stay informed, and no flashing tyre warning light will ever disturb your peace of mind.