What To Do If My TPMS Light Comes On

A 8-step guide on what you need to do is your TPMS (tyre pressure monitoring system) light comes on

Have you ever had an alert appear on your vehicle’s dashboard telling you that your tyre pressure is low? If you’ve experienced this, then your vehicle will be fitted with TPMS. These systems are very useful and can be found in all vehicles that have been manufactured since 2014.

But how do tyre pressure sensors work? And, more importantly, what do you do if your TPMS light comes on? Read our handy guide to find out more.

What is TPMS?

Tyre Pressure Monitoring Systems (shortened to TPMS) are fitted to modern vehicles to monitor tyre pressure - and report low pressure or tyre pressure imbalances on a vehicle.

Within the TPMS is a sensor that triggers a warning light when there is a drop in pressure of between 6-7 PSI - although some manufacturers set their warning lights to come on when sensors detect much smaller decreases, for additional peace of mind.

These devices can be used to determine whether your tyre is frequently leaking air, either through the rim or because of a slow puncture. Solving this problem quickly could reduce the chances of an accident occurring due to a blowout or a flat tyre.

How do car tyre pressure sensors work?

The two main types of TPMS are direct and indirect.

Direct TPMS

Direct TPMSs are the most common, as they’re more reliable. This system uses pressure sensors that are located within the tyre to track the pressure. Because of their location, they can track the exact pressure within the tyre, making them accurate and reliable.

When the pressure drops past a set parameter – usually 25% – a warning alert will appear on your dashboard. At this point, the car should be taken to a petrol station to have its tyres pumped up. Some TPMSs will even specify which tyre is low, so you don’t have to manually check them all.

These sensors are fitted with an internal battery, however, battery failure is the main reason TPMSs stop working. The more miles you do, the quicker the sensor will run down. Unfortunately, for them to work properly, they need to be sealed units – so you can’t simply replace the battery when it runs out.

Indirect TPMS

Indirect TPMSs don’t have their own sensor. Instead, they use another sensor that’s located inside the wheel, usually the anti-lock braking system’s sensor. This works by tracking the tyres as they revolve.

A tyre that is underinflated will have a smaller radius than a tyre that’s properly inflated, and therefore it will make more or irregular turns. This is how the sensor detects that the pressure could be low. This kind of system is less accurate, but is still able to tell you when a tyre requires more air.

As a whole, these sensors can be very beneficial. If your car is frequently telling you that one tyre is low, then it may have a slow puncture, or could be leaking air from the rim. You should take it to your local garage to have it looked at, and you might need to get a replacement.

Driving with under-inflated tyres could also have an impact on their lifespan - they may wear down more quickly, or even have an impact on your steering and fuel usage. To prevent this, you should ensure that your tyre pressure mirrors the manufacturer’s recommendation.

If you’ve re-inflated your tyre to the correct air pressure and the warning alert is still on your dashboard, you may have a faulty sensor that needs replacing. This is worth mentioning to your mechanic when you next visit.

Where are tyre pressure sensors located?

Direct TPMS sensors are located within the tyre, usually in the space between the tyre and the wheel rim. As indirect TPMSs use the sensor on the anti-lock braking system (ABS), this sensor is typically located near the brake disc. The wheel may need to be removed in order to gain access to the sensor.

Why is tyre pressure important?

So, why is the monitoring of tyre pressure important? Data published by the DfT shows there were 190 tyre-related KSIs in 2023 – up 29% from 2022 (147). The 2023 figure is also the highest number of casualties due to tyre defects since 2018.

So, to keep you, your passengers, and other road users safe, maintain your tyres, ensure your tyre pressure is correct, and keep an eye on your TPMS.

Another reason to ensure your TPMS is working properly on a regular basis is the potential MOT implication. Since early 2015 having a faulty TPMS can cause instant MOT failure if the TPMS dashboard light stays on to indicate a fault or problem with the valves.

Why the TPMS Light Might Stay On After Adjustments

If your TPMS light remains on after adjusting your tyre pressures, it could indicate an underlying issue. One common reason is a faulty TPMS sensor, often due to battery issues or physical damage. Direct TPMS sensors inside the tyre rely on small batteries, which can wear out with high mileage, while indirect systems linked to your vehicle’s anti-lock brakes may need recalibration.

Another reason could be a slow puncture or valve leak, where even small air losses cause pressure to drop consistently. Additionally, some vehicles require a manual TPMS reset after adjustments, a process detailed in your vehicle manual.

Environmental factors such as cold weather can cause tyre pressure to change, in turn resulting in the TPMS light staying on if the tyres remain below the optimal pressure.

How to reset your TPMS system

To reset your TPMS system, start by checking your vehicle manual for specific instructions, as this can vary depending on your vehicle. Typically, you’ll find the TPMS reset button beneath the steering wheel or within the dashboard settings menu.

Firstly, you want to start by turning on the ignition (for keyless vehicles, press the ignition button without pressing the brake).

Next, press and hold the reset button until the TPMS indicator light blinks several times, then release.

To complete the reset, drive at a steady speed of 20–25 mph for about 10 minutes, which allows the system to recalibrate with the updated tyre pressures. If the light doesn’t turn off, it may indicate a sensor issue, and it’s best to visit a Kwik Fit centre for further assistance.

Maintain your TPMS at Kwik Fit

At Kwik Fit, we believe in preventative maintenance. We replace the valve every time a tyre is removed from its rim. As the TPMS sensor is just a more complex form of valve, we can service all the various components of the sensor - thus ensuring TPMS valve integrity.

If your vehicle doesn’t have a TPMS, don’t worry - you can use our Tyre Pressure Search tool to determine your vehicle’s optimum tyre pressure, and ensure you stay safer on the road. If you have any other questions about your TPMS, contact your local Kwik Fit centre today and we can point you in the right direction.