TPMS Light On? What It Means and the Correct Tyre Pressures
A solid TPMS light means a tyre is significantly underinflated. A flashing light means the system itself has a fault. Check pressures against the door label.
By Galactic News Editorial · Published 2026-11-08T07:22:13+00:00 · Updated 2026-11-08T07:22:13+00:00
TPMS Light On? What It Means and the Correct Tyre Pressures
The TPMS light looks like a horseshoe with an exclamation mark inside it. When it stays on, at least one of your tyres is significantly underinflated. Check your tyres and their pressures as soon as possible. This guide explains what the light means, how to find the correct pressure for your car, and when the light signals a system fault instead.
What the TPMS Light Means
TPMS stands for Tire Pressure Monitoring System. It watches the air pressure in your tyres and warns you when one drops too low. The system is standard on passenger cars, light trucks, and vans from model year 2008 onward in the United States. Some 2006 and 2007 vehicles have it too. There are two types. A direct system uses a sensor inside each wheel, usually built into the valve stem. It measures the actual pressure. An indirect system uses the anti-lock braking wheel speed sensors. An underinflated tyre has a smaller rolling radius, so it turns faster. The system detects that difference. Under the federal standard, the light must come on when a tyre falls 25 percent or more below the recommended cold inflation pressure. On a car placarded at 35 psi, that threshold is about 26 psi. The light is a low-pressure warning. It is not a puncture detector. It says nothing about tread depth or sidewall damage. It can also stay dark while a tyre is five or six psi low. That is why a monthly gauge check still matters.
TPMS Light Guide: Solid Light vs Flashing Light
How the light behaves tells you what is wrong. A solid light means low pressure. The system is working and doing its job. Check the tyres and inflate them. A flashing light means something else. If the symbol flashes for 60 to 90 seconds at start-up and then stays on, the system itself has a fault. The light repeats that flash-then-steady sequence at each start-up until the fault is fixed. Common causes are a sensor whose internal battery has died, a sensor damaged during a tyre change, or a new set of wheels that was never programmed to the car. Sensor batteries last roughly 5 to 10 years and cannot be replaced on their own. The sensor must be replaced. While the light flashes this way, the system cannot warn you about a genuinely low tyre. Check pressures with a gauge until a qualified mechanic inspects the system. NHTSA advises contacting your dealer for an inspection when the light flashes.
Finding the Correct Tyre Pressure
The correct pressure is on your car, not on the tyre. Find the Tire and Loading Information label on the driver's side door edge or door frame. Your owner's manual lists it too. The number molded into the tyre sidewall is the maximum pressure the tyre can take. It is not the recommended pressure. Do not inflate to that number. Most cars list one pressure for the front tyres and one for the rear. Some list a different pressure for a fully loaded car. Use the figure that matches your load. Check pressures when the tyres are cold. Cold means the car has not been driven for at least three hours. Driving heats the tyres and raises the pressure reading. A reading taken after a drive will look higher than the true cold pressure. NHTSA recommends checking every tyre, including the spare, at least once a month. Cold mornings can trigger the light on their own. Pressure falls about 1 psi for every 10 degrees Fahrenheit drop in temperature. A tyre that was fine in summer may dip below the warning threshold on a cold night. The light may go out again as the tyres warm up. Even so, check the pressure. The tyre was close to the threshold for a reason.
What to Do When the TPMS Light Comes On
- Slow down and find a safe place to stop. Look at each tyre. A visibly flat or bulging tyre needs attention before you drive on.
- Check all four pressures with a gauge, including the spare if it has a sensor. Compare each reading with the door label.
- Inflate any low tyre to the recommended pressure. Use a petrol station air pump or a home compressor.
- Drive for a few minutes. The light should go out once the pressures are correct. Some cars need a short drive before the sensors report again.
- If the light stays on with correct pressures, or if it flashes, book an inspection with a qualified mechanic. Do not ignore a flashing light.
Never drive on a tyre that is visibly flat, even for a short distance. A flat tyre can come off the rim and damage the wheel. If the tyre looks badly deflated, fit the spare or call roadside assistance. If you find a nail or screw in the tread, do not pull it out. Leave it in place and drive slowly to a tyre shop, or fit the spare. Pulling it out can turn a slow leak into a fast one.
Why Correct Pressure Matters
Underinflated tyres are a safety issue, not a minor annoyance. A tyre that is 25 percent underinflated changes how the car handles. Braking distances grow. Steering feels vague. The tyre also flexes more, builds heat, and wears faster. NHTSA reports that tyres underinflated by more than 25 percent are three times more likely to be involved in a crash related to tyre problems. Proper inflation also saves fuel. NHTSA notes that correctly inflated tyres can save up to 11 cents per gallon and extend a tyre's average life by about 4,700 miles. Overinflation is also wrong. It makes the ride harsh and wears the center of the tread. It reduces grip on wet roads. The correct pressure is the one on the door label. Check it monthly, and the TPMS light becomes a backup, not your only warning.
Bottom Line
A solid TPMS light means a tyre is significantly underinflated. Check all four tyres with a gauge and inflate them to the pressure on the driver's door label. A light that flashes for 60 to 90 seconds and then stays on means the monitoring system itself has a fault. Book a qualified mechanic for that. The system only warns at 25 percent below the recommended pressure. A monthly check with a gauge catches the slow leaks it misses.