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One of the most important aspects of vehicle safety on the road is tire integrity. Unfortunately, some of us take these circular rubber wonders for granted. We get into our cars, crank the engine, and speed off without even bothering to check the integrity of our tires. Good thing modern cars now come with a really useful mechanism that alerts us to the status of the pressure in our tires. But for those who are not familiar with the system, getting that tire pressure warning light in your instrument panel can send waves of panic. It doesn’t have to be that way. Here’s everything you need to know about the tire pressure monitoring system in your car and what you should do in case the light does go on.

The Tire Pressure Monitoring System

Modern cars that are manufactured or built since 2007 already come integrated with a Tire Pressure Monitoring System that effectively monitors the air pressure in each of the vehicle’s tires. Each wheel comes with an air pressure sensor that is connected to the car’s onboard computer. This sensor keeps track of the changes in the pressure inside the individual tires.

Depending on the calibration or how the system was set-up by the vehicle manufacturer, the TPMS can trigger an alarm in the event that the air pressure is 25% lower than the recommended cold tire air pressure by the vehicle manufacturer. Cold tire pressure is generally described as the pressure within the tires when it has not been in use for a minimum of 3 hours.

When the TPMS ‘senses’ a critical reduction in air pressure, it automatically activates the warning light on the instrumental panel in the vehicle.

Reason for the TPMS in a Modern Car

In the past, the only way one can check if the tires are underinflated or overinflated was to inspect each tire visually. In many cases, even visual inspection alone cannot give you a clear picture of just how much air pressure you have left in the tires. As such, you’d have to use an air pressure gauge to get a correct reading. If it is underinflated, then you have to add air pressure.

This somehow changed when the American Congress passed in the year 2000 the Transportation Recall Enhancement, Accountability and Documentation (TREAD) Act which required all vehicles that are to be sold starting in September 2007 to be fully equipped with a Tire Pressure Monitoring System.

The reason for the creation and passing of the TREAD Act has its roots in 1996 when a number of state agencies and offices in Arizona reported an increasing number of cases related to tread separations and tire blowouts in Firestone tires fitted into the official vehicles of these government offices.

In the years that followed, at least 200 people lost their lives because of underinflated tire-related issues on Firestone tires fitted to Ford Explorers. Reports said that tire failure was caused by intense heat buildup that was deemed secondary to tire underinflation.

It is for this reason that the TREAD Act was drafted and enacted into law, providing the impetus for the integration of a TPMS in the modern car.

How the System Works

Modern cars are electronically controlled. The moment you turn on the car key, the onboard computer immediately performs a very quick diagnostic of your vehicle’s current status. That is why you will see all of the vehicle’s warning indicator lights – the TPMS included – on the instrumental panel light up. These lights also automatically turn off once the diagnostics has been completed, usually with 2 to 3 seconds.

There are two types of TPMS that the car’s onboard computer has to synthesize data from. These are the direct and the indirect systems.

In the direct TPMS, a combination of pressure sensor and electronic transmitter is located inside the wheel assembly or in the tire itself. The system monitors the air pressure within the tire. If it senses that the air pressure is below 25% the recommended tire pressure, it sends an electrical signal to the computer which activates the TPMS warning light in the instrument panel. An audible sound is also produced to get your attention. Some systems can indicate which of your tires has low air pressure while other models can provide you with the precise air pressure within each of your tires.

The indirect system is dependent on the integrity of speed sensors on the wheels. These are made integral components of a car’s anti-lock brake system or ABS. The car’s computer continuously analyzes data sent from these sensors and monitors and change in tire size secondary to a reduction in tire pressure. If it senses a reduction in tire pressure by at least 25%, it triggers the TPMS warning light on the instrument panel.

What to Do When the Tire Pressure Warning Light Turns On

We know that the moment you turn on the key to your engine, the different indicators in the instrument panel will light up. This includes the TPMS. But what if it remains lit while the other indicator lights have already turned off? How about other instances of the warning light turning on while driving? What do these mean?

  • Stays On

If the TPMS warning light stays illuminated after starting your car and the rest of the warning indicators have already turned themselves off, it is best not to hit the road. If your system comes with an indicator as to which tire is affected, take note of the affected tire. Turn your engine off and manually check the tire pressure. If your system doesn’t come with visual indicators of the problematic tire, then you will have to check the air pressure of each individual tire.

  • Flashes, then Stays On

If, after turning the ignition of your car, the TPMS warning light flashes for about 60 to 90 seconds before it stays illuminated, this is usually a sign that the system is not in its optimum operating functionality. Again, check your tire’s air pressure with a tire gauge. Once you’re sure that you’ve got your tires inflated to the correct pressure, you can drive to an auto repair shop to have the TPMS checked.

  • Lights On While Driving

If the TPMS light suddenly turns on while you’re driving it usually means that one of your tires has reached its critical point that triggered the system. This is especially true if the light stays on while driving. If you have a portable tire pump, pull to the side of the road and add air pressure into the affected tire. If you are not sure which tire is affected it is crucial that you measure the pressure of each tire using a tire gauge. If you don’t have either a tire gauge or a tire pump, it is best to call for roadside assistance rather than risk driving on an underinflated tire.

  • On-Off

If the TPMS light turns on and off it is often an indication that your tires are nearing the threshold air pressure. For example, if the threshold is 25%, then the pressure may already be at 24%. This on-off behavior of the warning light can be due to fluctuations in the temperature inside the tires. If it is cold, there is less pressure and this can activate the system. If it is warm again, then the pressure rises and the system goes off. If this is the case, then you will have to individually check the pressure in each tire. However, make sure to take the measurement only when the tire is already cold. That usually means leaving it there for about 3 hours before reading the pressure. Inflate the affected tire to the correct pressure.

False Alarms

No matter how advanced these technologies are they’re not exactly immune to failure. It is still very possible that the TPMS warning light will turn on even though there is no actual loss of air pressure in the tires. This can happen if there is a faulty sensor. If the warning light turns on and you’ve checked the pressure in all the tires and everything is how they should be, then your problem is definitely related to a malfunctioning sensor or transmitter. This should be inspected and evaluated by a licensed mechanic immediately.

Optimizing the Benefits of Having a TPMS

The TPMS is an invaluable tool for modern vehicles as it gives you an idea of the presence of a problem. However, it will still be you who will address these problems. As such, here are some ways you can optimize the benefits afforded by TPMS.

  • Invest in a good quality compressor or tire pump and tire gauge.
  • Always check the tire pressure when the tires are cold to get the most accurate readings.
  • Keep your tires properly inflated and have them regularly inspected at least every month.
  • Read your owner’s manual to learn more about the type of TPMS installed on your vehicle including troubleshooting.

The tire pressure warning light is a very useful system that can help improve vehicle safety on the road. Learning how to interpret the different illuminated conditions can help you determine your next move.

Sources:

  1. Tire Pressure Warning Light: What It Means, and What to Do About It – Repair Pal
  2. How to Check Air Pressure in Tires – wikiHow

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