Feeling the pressure

TPMS is commonplace now, and Gareth Banks is reminding you that there are consequences come MOT time if it’s faulty

Published:  18 May, 2020

Issues with tyre pressure monitoring systems will become much more prominent and regular in the majority of workshops all over the UK. Since 2014, every car sold new in the European Union was required has to have a form of TPMS. There is no way of escaping it. As a technician you can try and hide from it if you like, but it will find you and it will make your brain engage when that little warning light ‘pings' on the dashboard.  
The thing that a lot of techs don't know is that the first form of TPMS was first put into practice in the late 1980s, so it is not as if it’s a new idea. Back then, it was mainly for high-end luxury cars. Now a very high percentage of low-priced to mid-range priced vehicles are fitted with a TPMS system. You can even buy a retro-fit system and put it onto your motorcycle if you wanted to!

There are two different types of monitoring systems. The first is a direct system in which the sensors are held within the wheels. These send a radio signal to the car and this is converted into a real-time display on the dashboard for the driver to keep a close eye on all of the pressures individually. The second is the indirect system. This one cannot show you a real-time value as there aren’t any TPMS sensors to send a radio signal back to the car. Instead this works via the cars wheel speed sensors/ABS sensors, to put it simply- it counts the  rotations of each wheel and recognizes a fault if one wheel turns quicker than the other three. Clever or what? Well, not really, if all four tyres lose pressure.

Prod and cons
When it comes to TPMS pros and cons, my personal thoughts are that these systems, particularly the direct system will make for safer roads and therefore save lives. Not only that, the fact is that it is going to save your tyres, and by keeping the optimum pressure in them,  saving your tyres will save you money, and if you save your money you will then be able to afford to buy new sensors if (when) they break... and they do break, whether it’s the core (due to bad practice when fitting tyres and not replacing something as simple as the core and the valve cap) ,a leak from the base of the stem or simply the battery going flat inside a sensor... (majority not interchangeable).
The simple fact is they do go wrong sometimes. Besides the main disadvantage of the indirect system that I mentioned earlier, if they do go wrong and it is obvious that the TPMS system isn’t working correctly, come MOT time the car will get a major fail. However, if the car is registered before January 2012, this doesn’t matter, which probably wasn’t the best decision ever made. I think any car equipped with a TPMS system from the factory should have it working. Simple as that, but that’s just my opinion.

If one or more pressures are low and the tyres look ‘obviously Under Inflated’ then that induces a pass with a minor defect. The facts is that thousands of accidents and hundreds of deaths occur every year due to under inflated tyres resulting in tread separation and ultimately failure of the tyre.
In short, tell your customers if they want better fuel efficiency, better handling and optimum braking, they might want to check their pressures, even when the MOT is not looming.


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