TPMS Light On in Cold Weather: What It Means and What to Do

If your TPMS light is on in cold weather, you are not alone. The first real cold snap of fall in Calgary sends a wave of drivers to tire shops asking why the little horseshoe-shaped warning just appeared. Most of the time the cause is simple physics: cold air takes up less space, so tire pressure drops. Sometimes it points to a leak or a failing sensor. Here is how to tell the difference and what to do about it.

Why the TPMS light comes on in cold weather

Tire pressure changes with temperature. As a rough rule, a tire loses about 1 psi for every 5 to 6°C drop in temperature. If you set your tires to 35 psi on a 20°C afternoon in September, then walk out to a -10°C morning in October, those tires may be sitting at around 30 psi without a single leak.

Most tire pressure monitoring systems trigger a warning when a tire falls about 25 percent below the recommended pressure. A tire already a little low can cross that line on the first cold morning. That is why Calgary shops see a spike in pressure light questions every fall, and again during a hard cold snap when temperatures plunge toward -30°C.

Solid light vs flashing light

The way the light behaves tells you a lot.

• Solid light: at least one tire is below the warning threshold. Usually low pressure, from cold air or a slow leak.
• Light that goes off after driving: the tires warmed up and pressure rose above the threshold. They are still low when cold and need air.
• Flashing light at startup that then stays solid: the system has detected a fault, such as a dead sensor battery, a damaged sensor or a sensor the car does not recognize.

What to do when your tire pressure light comes on

Do not ignore it, but do not panic either. Follow these steps.

1. Look at your tiresWalk around the vehicle. If one tire is visibly flat or much lower than the others, do not drive on it. Put on the spare or call for help.
2. Check pressure with a gaugeUse a reliable gauge on each tire, ideally before driving when the tires are cold. Some vehicles show individual pressures on the dash.
3. Fill to the door placard specUse the pressure on the sticker inside the driver's door jamb, not the maximum printed on the tire sidewall.
4. Drive and watchMany systems need a few kilometres of driving to reset. If the light goes out and stays out, you are done.
5. Recheck in a few daysIf one tire keeps losing pressure, you likely have a slow leak that needs attention.

Should you add air when it is cold outside?

Yes. Always set pressure based on cold tires at the temperature you will actually be driving in. If you inflate in a heated garage at 18°C and then drive into -20°C air, pressure will drop again once the tires cool. For the most accurate reading in winter, check pressure outside or right after pulling the car out, before driving.

Underinflated tires are a real problem in winter. They flex more, generate more heat, wear the shoulders faster, reduce fuel economy and make steering feel vague on snow. They are also more prone to damage from potholes during the freeze-thaw cycle.

When a TPMS light on in cold weather is not just the cold

If you fill all four tires and the light comes back within a day or two, something else is going on. The most common culprits we see at our NE Calgary shop are:

• A nail or screw in the tread causing a slow leak, which can often be fixed with a proper tire repair
• A leaking valve stem or TPMS sensor stem corroded by road salt
• Bead leaks where the tire meets a corroded or bent rim
• A sensor with a dead internal battery, typically after several years of service
• A new set of wheels or winter tires without sensors, or with sensors the car has not learned

TPMS sensors and winter tire sets

If you run a separate set of winter tires on their own rims, those wheels need their own TPMS sensors for the system to work. Without them, the light will flash and then stay on all winter. Some vehicles need a relearn procedure after swapping sets so the car recognizes the new sensor IDs.

We handle TPMS sensor replacement and relearn and can check sensor health during your seasonal tire change. If a sensor battery is getting weak, replacing it while the tire is already off the car is simpler than doing it separately later.

Can you drive with the tire pressure light on?

You can drive a short distance carefully to get air or reach a tire shop, as long as no tire is flat or visibly low. Driving for days or weeks with the light on is not a good idea. Low tires wear unevenly, hurt braking on snow and can overheat on the highway. And if the light is on for one tire, you will not get a warning if a second tire starts losing air.

If you are in NE Calgary and cannot find the cause, stop by 227 41 Ave NE Monday to Saturday between 9 and 6, or call (587) 894-3516. We will check pressures, look for leaks and test the sensors so you know exactly what is going on.

Tire Pressure Light Won’t Go Off?

We can check pressures, find leaks and scan or replace TPMS sensors in NE Calgary.

Call (587) 894-3516TPMS Service