The Complete Guide to Tyre Pressure Monitoring Systems (TPMS)
In this guide, we’re going to an in-depth look at TPMS, covering areas such as:
- What is TPMS, and how does it work?
- The purpose of TPMS
- The different types of TPMS
- How to fix common TPMS issues
- Maintaining a TPM system
- OE and aftermarket tyre pressure sensors
- The tools you will need to service tyre sensors
What is TPMS, and how does it work?
A tyre pressure monitoring system is used to check and manage your vehicle’s tyre pressures. TPMS is an essential safety feature for your car, and all car manufacturers must have some form of TPM system built-in to their new vehicles.
There are two different types of TPMS, and each type works differently:
- Direct TPMS
- Indirect TPMS
This system uses specialised sensors to monitor the tyre pressure in each wheel directly. The sensors send signals to the ECU using a wireless connection. Direct TPMS is highly accurate and will detect any small changes in tyre pressure quickly. However, if a sensor becomes faulty, then it will require specialists tools and equipment to resolve.
This system doesn’t directly measure the tyre pressures in each wheel. Instead, it uses the cars ABS sensors to check the wheel speed and then assesses this information to determine the cars tyre pressures. This type of system is straightforward and does provide an acceptable solution to keeping your tyre pressures at a suitable level. One major flaw, however, is that it’s slow to react to changes in tyre pressure.
The purpose of TPMS
The European Union introduced laws regarding tyre pressure monitoring systems in 2012. These laws were put in place to improve road safety for drivers and reduce carbon dioxide emissions.
A TPM system will warn users when their tyres are under-inflated and will help prevent any road accidents caused by low tyre pressures.
Figures from the EU show that under-inflated tyres are a contributory factor in 9% of all fatal road accidents and 41% of road accidents resulting in serious injuries.
By keeping your tyre pressures at a suitable level, you will have a positive on the environment by reducing fuel consumption.
Figures from the EU estimate that worldwide, 20 million litres of fuel is burnt each year unnecessarily due to low tyre pressure. That’s two million tonnes of carbon dioxide into the atmosphere every year!
Benefits of TPMS
As we’ve already established, having the correct air pressure in your tyres will help you in several ways:
- It will reduce the amount you spend on fuel every month. An underinflated tyre creates more rolling resistance and therefore uses more fuel.
- It will improve your safety on the roads by ensuring you don’t have any accidents caused by low tyre pressures, such as a blowout.
- It will prevent uneven tyre wear and therefore increase the lifespan of your tyres.
- It will benefit the environment because you won’t be burning excessive amounts of fuel which reduces your carbon footprint.
Maintaining a TPM system
All car manufacturers recommend that you should service your TPMS sensors every time you have a tyre changed. In general, your sensors should have a seven-year lifespan before the battery is due for replacement. But tyre pressure sensors can fail prematurely as a result of corrosion, accidental damage, or weather conditions.
The structure of a TPMS sensor
As stated previously, all car manufacturers recommend that you replace your TPMS hardware every time you have a tyre changed. This service doesn’t mean you need to replace the actual sensor, but rather the components that keep the sensor in place, i.e. the valve, collar and grommet.
If you have rubber (or snap-in) valves that support the sensor, then you only need a new valve unit during servicing. Unfortunately, there are a large variety of rubber valves used for TPMS, and they all vary in structure. However, if the tyre garage is serious about their trade, then they should keep them all in stock. Rubber valves typically have a short life span compared to their metal alternatives, and so it should be standard practice to replace them during a tyre change.
Metal (clamp-in) valves have a few more components than a rubber valve. As well as having a valve unit, they also have:
- A rubber grommet (this acts as an air seal)
- A washer (to guard both the wheel and the valve collar during fastening)
- A valve collar (this supports the base of the valve and allows it to be fastened to the wheel).
If you loosen a clamp-in valve, then you must install a whole unit afterwards. The rubber grommet that provides an air seal has a ‘memory’, and so if you remove the valve, then the grommet cannot be used again.
OE and aftermarket sensors – What’s the difference?
Original equipment (OE) sensors comes from the same manufacturer who built the sensors for the vehicle during the assembly process. OE sensors are pre-programmed, so there is no need for specialist tools during installation.
Aftermarket sensors provide an alternative replacement to OE sensors and are capable of being programmed to a wide range of car makes. They are cheaper to purchase than OE sensors, but they may require specialists tools for programming.
Types of aftermarket sensors
There are five different types of aftermarket sensors on the market:
- OER (Original Equipment Replacement)
- Cloneable sensors
- Configurable sensors
- Multi-application sensors
- Programmable sensors
These sensors are designed specifically for a car make or model. They are pre-programmed and therefore require no diagnostics for installation.
These are blank sensors which you can copy sensor IDs too, but nothing more. A cloneable sensor used primarily for spare sets of wheels (i.e. summer and winter wheel swaps). These sensors do require programming, but they don’t need to be written to the ECU as they possess the same ID as the current sensors.
This type of sensor can be both cloned from another sensor, or programmed as a new sensor for a specific make or model. During programming, configurable sensors aren’t limited to a particular car make like an OER sensor is. Instead, it can be set up to work with almost any vehicle on the market. A T-Pro hybrid sensor, for example, covers 99% of new cars.
A multi-application sensor effectively sends out multiple signals to the vehicles ECU, but the car will only recognise one of those signals. It’s not a great option, and we wouldn’t recommend using it.
The final option is programmable sensors. These can’t clone ID from other sensors and so must be written onto the ECU. They have a built-in memory which allows it to be programmed to a specific vehicle make or model. This type of sensor requires diagnostic tools to write the new sensors to the ECU.
TPMS re-learning procedures
When you’ve replaced a tyre sensor or changed its position, you may need to perform a re-learn on your TPMS system. A re-learn procedure updates your car on the current location and ID of the sensors. To execute a re-learn, you must put your vehicle into “learn” mode. This procedure varies between manufacturers, but there are only three types of re-learn methods:
A trigger re-learn requires the technician to perform a specific sequence of actions to trigger the car to learn the new sensors. A typical example would be a late 2014 ford fiesta, whereby you would need to alternate the position of the key in the ignition as well as pressing some auxiliary buttons. If you do manage to complete all the necessary steps in the allotted time frame, then the car will be ready to learn the new sensors.
This type of re-learn requires no special tools or equipment when installing new sensors. Additionally, you can perform a wheel rotation and change the position of the sensors without any issues. A car with auto re-learning will reset itself after a few miles of driving. Mercedes and BMW typically have auto re-learn functionality.
An OBD2 re-learn requires both a TPMS tool and an OBD2 adaptor. It transfer’s the information directly to the cars ECU. The technician must scan all the sensors in the correct order before choosing the re-learn function and following the instructions on the screen.
This type of re-learn is now becoming more common amongst car manufacturers as it’s the fastest and easiest method to install new sensors to a vehicle.
TPMS Tools & equipment
With so many TPMS tools on the market, it’s hard to know which one is the best to use. We use the ATEQ VT56 for all our TPMS services.
And regarding TPMS sensors, we recommend the T-Pro Hybrid sensors as their coverage is unmatched by other manufacturers. Unfortunately, however, this technology does come at a price, and you would easily be looking at paying over £1000 for a quality TPMS tool. So, unless you’re a professional garage, you’re better off having your tyre sensors programmed by a third party.
How to programme a TPMS sensor
To code a tyre pressure sensor, you will need the necessary diagnostic equipment. You will also need a TPMS sensor that is either A) programmable or B) configurable. Additionally, the car you’re servicing must be able to re-learn new sensors via the OBD2 port. If you have fulfilled these requirements, then the next few steps are relatively simple.
Step 1 – Programme the TPMS sensor, so it matches the vehicles make, model and year. The ATEQ VT56 tool makes this extremely simple, and it only takes a few seconds.
Step 2 – Install the TPMS sensor to the wheel and complete the tyre installation process. If you’re not an experienced tyre fitter, then you will need help with this step.
Step 3 – Scan all the sensors on the car in the correct order.
Step 4 – Rewrite the ECU so that it reads the new sensors (Use the OBD2 port for this).
Step 5 – Go back around the car and activate the sensors again by scanning them, confirming their final position and tyre pressures.
Step 6 – Start the car and look for any lights on the dashboard.
If you’ve followed the steps correctly, then there should be no issues with the vehicle. If you do have any problems, then I would suggest checking the following:
- The new sensor (is it broken or providing a weak signal?)
- The tyre pressures (are they correct according to the manufacturer specifications?)
- The other sensors (did you scan them correctly before and after installation?)
- The vehicle (did the information transfer successfully? Does it require a period of driving afterwards to complete the re-learn?)
If you’ve checked everything and still have a problem, then I would suggest getting in touch with a member of our team for advice on the next step.
A final note on TPMS
TPMS is a great feature and has many benefits to both the driver and the environment. Yes, it requires more maintenance and expense, but this is insignificant in comparison to the bigger picture. TPMS helps to save lives, save tyres, save fuel, and save the environment. With the right servicing, your TPMS should last for years without any issue. By the time it does come for replacing, you will have saved enough money on fuel to cover the difference. And if you’re looking for a tyre garage that will keep your TPMS serviced properly, then get in touch. Our technicians are IMI qualified, and we carry all the necessary equipment to repair and replace TPMS on any car make & model. We also have a five-year warranty on every TPMS sensor sold. So if you have any issue within that period, we will fix it for free! And to add to all of this, we also provide a mobile fitting service at your convenience.
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