You’re ready to leave for work or school, you start backing out and suddenly you see this funny symbol that looks like an exclamation point, inside of a horseshoe, with ridges on the bottom that emulate tire treads. You realize the Tire Pressure Monitor System (TPMS) light came on and you may immediately assume you have a flat tire, but this isn’t always the case. While it’s possible you have a flat tire, it could just be the effects of cold morning air, low air pressure, or a malfunctioning sensor altogether.
The purpose of the TPMS is to monitor the air pressure in each tire. So, when does the TPMS light come on? If one or more of the tire’s air pressure drops below the specified range, as determined by the manufacturer, the light may come on. Do you know what to do if the light comes on in your car?
Why Your Car Needs TPMS
Tire care, including proper tire inflation, is vital to your safety on the road. Properly inflated tires maintain contact with the road which is essential to vehicle handling. Properly inflated tires:
- Reduce rolling resistance to increase fuel efficiency.
- Prevent excessive tread movement, extending the life of the tire.
- Increase the tire’s ability to disperse water when encountering wet surfaces, decreasing the likelihood of hydroplaning.
Properly inflated tires offer better support for the weight of the vehicle, provide more cushion and comfort when traveling over rough terrain, increase dissipation of heat generated while rolling, increase the driver’s control of the vehicle for acceleration, braking, and cornering, and increases the life of the tire.
Over or under-inflated tires can cause premature wear that may lead to replacement sooner rather than later. Overinflated tires reduce traction, accelerate wear, and are unable to make proper contact with the road by wearing down in the center tread area. Underinflated tires affect your safety and your vehicle’s reliability on the road. Driving on underinflated tires creates excessive heat that may cause blowouts and result in serious accidents.
As a result of numerous serious crashes and their fatal effects, the U.S. Congress enacted the TREAD Act of 2000, to require all vehicles by 2008, be equipped with TPMS to alert drivers of tires that may be underinflated by 25% or more.
What To Do When the TPMS Light Comes On
When the TPMS light is illuminated, while you shouldn’t panic, you should be concerned, especially if you’re driving down the road. Here’s what to do in the event that the light comes on:
- Pull over to a safe area to check tires. If you are traveling at highway speeds and the light comes on suddenly, maintain a firm grip on the steering wheel with both hands, as your tire may be experiencing a blowout. Decrease your speed and safely make your way over to the right side of the road.
- Walk around your vehicle and check for flat or blown out tires. If you do not identify this sort of trouble, using a tire gauge, check the air pressure in each tire to ensure they meet the manufacturer’s recommended specifications (specifications can be found on the frame of the driver’s side door).
- Take your vehicle to the nearest service center or locate a nearby gas station’s air supply area and fill the tires to the proper pressure.
TPMS Light Goes On and Off Intermittently
When tire pressures are near the range that triggers the light to come on, fluctuating ambient temperatures may be to blame for causing the light to turn on and off. This issue usually occurs when the tire’s air pressure decreases overnight due to a drop in temperatures causing the light to come on. Subsequently, the light may turn off from increased pressure as a result of warmer temperatures or heat generated while moving.
Keeping steady tire pressure can be a challenge when daytime and nighttime temperatures vary so greatly. As the temperature fluctuates, so too does the pressure in the tires. In the morning hours, the air temperature begins to rise from the overnight lows, and tires have cooled significantly from being parked. Morning time is when your tire’s air pressure is at its lowest. It’s possible that the pressure is just slightly below the threshold that triggers the light to come on. Once the vehicle is driven and the tires heat up, the pressure will increase pushing the pressure back over the acceptable range causing the light to turn off.
If the light remains off, it’s likely that the outside temperature is warm enough to keep the pressure above the threshold. In either case, it’s best to check the air pressure and add air to any tire that may be low on air.
TPMS Light Flashes and Stays On
A TPMS light that flashes between 60 – 90 seconds each time the car is started and remains on, may indicate that the system has malfunctioned and needs to be inspected by an automotive technician. Don’t wait to take your vehicle in for inspection. The TPMS will be unable to alert you to low tire pressure, which could pose a danger to you on the road.
What Causes Air Pressure In Tires to Change?
- Time. Osmosis of air through the tire’s casing can cause a minimal loss of air per month. Over time, that loss can equate to significant changes in PSI (Pounds per Square Inch).
- Slow leaking punctures in the tread such as a nail in a tire’s hollow area can cause a loss of 2-3 PSI per day.
- Leaking valves stems or cores.
- Through use. Running over objects, hitting curbs, or frequent travels over potholes.
Note: Many vehicles today use pure nitrogen as opposed to just air in the tires. The benefit of the use of nitrogen is that it helps maintain a more consistent pressure compared to tires with regular air. Nitrogen doesn’t seep through the rubber as easily and contains less moisture allowing a more consistent pressure with variable temperatures.