How do Tyre Pressure Sensors (TPMS) work?

How do Tyre Pressure Sensors (TPMS) work?

With thousands of cars failing their MOT Tests every year, due to defective Tyre Pressure Monitoring Systems (TPMS), owners are facing unexpected repair bills totalling hundreds of pounds.

The main culprit is faulty TPMS sensors, which are used on many (but not all) vehicles that boast this technology. These sensor units are integral with the tyre valve and lead a hard life. As they are exposed to rotational forces, air pressure and good old British weather, they tend not to last forever. The problem is that many people ignore TPMS sensors, until they develop a fault.

What goes wrong with TPMS sensors?

Apart from their integral batteries running flat after 8-10 years, corrosion is the main cause of failure. This can not just rot the electronics but the tyre can also start to lose pressure gradually, especially if the seals between the valve and wheel rim become compromised.

In severe cases, corrosion and general neglect can result in the valve disintegrating, resulting in a sudden and potentially lethal flat tyre, especially if the car is being driven at the time.

Certain tyre sealants also ruin tyre pressure monitoring system sensors, by clogging up their pressure sensor holes. Should you carry an emergency can, ensure that it is TPMS compatible. Consider also that tyre sealants should not be used beyond their expiry dates.

How much does TPMS servicing cost?

To reduce these risks, GEM recommends strongly that you ask a tyre fitter to service your TPMS valves, whenever the tyres are removed from the rim. Firstly, the technician will remove and inspect the sensor. Dependent on the design and degree of damage, the sensor's stem, washers, seals and internal core will be renewed. The sensor unit itself is the most expensive part to replace, not just in terms of the part but also because a new virgin unit requires activating and programming after tyre pressure sensors are installed.

Costs will vary between garages and different makes and models but the majority of them charge between £10 and £20 to service each sensor.

How do I make TPMS sensors last longer?

Apart from maintaining the valves, consider that many metal valve caps, sold as accessories, can corrode the tyre pressure monitoring system valve stem. In extreme cases, the two metals can fuse together. Whenever fitting replacement metal valve caps, check with the vendor that they are compatible with your TPMS valve stem.

The internal sensor batteries are sealed within the sensors and cannot be replaced. Should they become exhausted, the whole sensor will need replacing. The more often you receive dashboard warnings about low tyre pressures, the faster the sensor batteries will deplete. Therefore, regular tyre pressure checks are beneficial not just for your safety but also for maximum TPMS sensor life.

How can I save money, replacing TPMS sensors?

Eventually, you will have to replace the sensors. Disabling the system is not a safe option and might invalidate your insurance, as well as causing most cars to fail the MOT Test. Naturally, shop around for the best tpms system deals. Yet, consider that more cost-effective new sensors can be programmed using data taken from the original units, which also presents a cost saving. Therefore, enquire if your tyre fitter offers this option, too.

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