The Tire Pressure Monitoring System (TPMS) is a technology that continuously monitors the inflation pressure of the tires on the wheels. If it falls below a certain safety threshold, it alerts the driver.
This is a device that is mandatory in new cars sold in the European market since November 1, 2014 and is included along with other basic safety systems, such as stability control (ESP), ABS, airbags, seat belts, etc.
Knowing the tyre pressure is vital to avoid accidents. It is estimated that 40% of accidents related to tyre failure are caused by driving with tyres that are underinflated. It also has other advantages for the driver, as having tyres with the correct pressure helps to reduce fuel consumption and CO2 emissions from the car: with 0.3 bar less pressure, consumption increases by 1.5%.
How TPMS works
When the system detects that a wheel does not have the correct pressure, a warning light on the instrument panel lights up. It is usually yellow with the image of a tire and an exclamation mark or simply with the letters TMPS in orange.
These are the simplest systems. In the most advanced ones, the on-board computer provides information on the exact pressure and temperature of each wheel, also warning if any of them does not have the correct pressure.
How is the pressure known? It depends on the meter type that the tire has:
- Direct TPMS: Collects pressure data directly from the tire valve via dedicated sensors. This information is encoded and transmitted… then processed to be displayed on the dashboard in near real time.
- Indirect TPMS: Uses the ABS system to approximate tire pressure. A substantial distance must be driven before the alert is generated so that the ABS sensors can detect which wheel is spinning more than the others (assuming the loss of pressure). It also requires the driver to recalibrate the device after changing tire pressure or changing a wheel. This means that the driver has control over a vital safety feature of their vehicle, something that is not the case with other features such as airbags or ABS. For To function effectively, all four tires must be inflated to the correct recommended pressure and be in optimal condition.
Obviously, the direct TPMS system is preferable and this is indicated by various surveys of drivers around the world, since the main value of the technology is to warn of a lack of care in the pressure… and if it occurs in all four wheels at the same time – which can happen – a indirect system will not warn about it.
When the vehicle is moving, the tyre pressure and temperature are monitored every few seconds. The TPMS sends the readings continuously to the on-board computer. If the car is stationary, measurements are taken at longer intervals and readings are only transmitted when there is a change in pressure.
TPMS Problems
First of all, remember that this technology does not prevent Check the pressure regularly of the tires. It is a routine, simple operation that even TPMS system manufacturers recommend, since there is no foolproof system. You have to take into account that the rims have sensors with batteries, integrated into the valve (or even inside the tread). And that is delicate:
- Hits: : Contact with the rims can damage the sensors, so avoid sudden contact with curbs or contact that may occur when removing the tyre when it is time to change it.
- Valve caps: They prevent dirt or moisture from entering the tyre valve… vital in these cases as they also include electronic sensors. Check from time to time that they are in good condition… or that they have not been stolen. Valves with integrated sensors have a metal neck to prevent the valve from vibrating at high speed, so they need a rubber seal to seal, with a certain torque that must be checked from time to time (as well as the seal).
Even if they don’t break down, they have a shelf life and can lead to some additional problems:
- Sensor battery: They account for the majority of problems with the TPMS, since, like all batteries, they eventually run out. Their useful life is about five years and requires the entire sensor to be replaced.
- Deprogramming: If the car battery is dead or the car is jump-started, the control unit may lose the coding of the sensors that communicate with it via radio. In this case, they must be recoded in the workshop using a diagnostic unit. In some cases, errors may occur if the car drives through an area with frequency inhibitors or a strong magnetic field, such as a high-voltage pylon.
- False alarms: We have had a false alarm on occasion after leaving the car parked, as it may be that a wheel has been exposed to the sun. Normally, when you drive for a while, as soon as the temperatures equalise, the warning disappears.
