Why Your TPMS Light Comes On in Cold Weather
The first frosty mornings of fall bring a familiar sight for a lot of drivers in Cambridge, Kitchener, Waterloo and Guelph: the tire pressure warning light glowing on the dash. Most of the time nothing is broken. Cold air is simply doing what cold air does. Here's why it happens, and what to do when it does.
Cold weather lowers your tire pressure
According to Transport Canada, tires lose about 7 kPa (1 psi) for every 5°C drop in air temperature. They can also lose about 14 kPa (2 psi) a month through normal permeability, even without a puncture.
Put those together and a tire that was set correctly on a warm September afternoon can be noticeably low on a cold October morning. That's often enough to trigger your tire pressure monitoring system (TPMS).
How your TPMS works
Transport Canada describes two common types of tire pressure monitors:
Indirect systems use the ABS sensors to compare wheel speeds. An under-inflated tire turns slightly faster than the others.
Direct systems use a pressure sensor mounted in each wheel.
Transport Canada also notes that some systems only warn you once a tire is significantly under-inflated, when it may already be close to failure, and that large outdoor temperature swings can set off the low-pressure warning. So treat the light as a reason to check your tires right away, not as something to ignore until spring.
Light on in the morning, off after a drive?
Tires warm up as you drive, and warmer air means higher pressure. Michelin Canada points out that this is why the TPMS light can come on on a cold morning and go off after you've been driving for a while. The light going out doesn't mean the problem is solved. It usually means your tires are sitting right at the edge of too low when they're cold, so it's time to top them up.
What to do when the TPMS light comes on
When it's safe, pull over and look at all four tires. If one is flat or obviously low, don't keep driving on it. Read our flat tire repair page for what to do next.
Check the pressure with a good-quality gauge. Transport Canada recommends measuring when tires are cold, meaning the vehicle has sat for at least three hours or been driven less than 2 km.
Inflate to the pressure on your vehicle's tire information label, usually on the edge of the driver's door, the door post, the glove box or the fuel door, or in your owner's manual. Don't use the maximum pressure printed on the tire sidewall. That's the pressure needed to carry the tire's maximum load, not your vehicle's recommended pressure.
Check the spare too, if your vehicle has one.
Keep an eye on it. If the same tire keeps losing air, it may have a slow leak and should be looked at.
A steady light vs. a flashing light
On many vehicles, a steady light means low pressure, while a light that flashes for about a minute and then stays on means the system itself has a fault. Transport Canada notes that a malfunction warning can also appear when tires are changed or rotated and the system isn't reset. Your owner's manual explains exactly how your vehicle's system behaves.
If the light stays on after you've set every tire to the right pressure, or it's flashing, it's time for a TPMS sensor check.
Switching to winter tires? Think about your sensors
October and November are changeover season in Ontario, and that's a good time to make sure your TPMS is working properly. At SVS Tires & Wheels we service TPMS sensors as part of every tire installation, and we service and reset them when we install new wheels, such as a winter wheel and tire package.
Getting ready for the season? Browse our winter tires, book a seasonal tire swap, or ask about tire storage for your off-season set. On a tighter budget? Take a look at our new economy tires, or use the Find Tires by Size search to see options for your vehicle. Every install is balanced with Road Force balancing equipment.
Don't rely on the light alone
Transport Canada is clear that tire pressure monitors don't replace regular maintenance. Check your tire pressure at least once a month, and before long trips. It only takes a few minutes, and in an Ontario winter it's one of the simplest things you can do for safer driving.
TPMS help in Cambridge, ON
Have a tire pressure warning you can't explain? Visit SVS Tires & Wheels at Units 7-8, 990 Bishop St N, Cambridge, ON N3H 4V7. We're open Monday to Friday, 10:00 AM to 5:30 PM. Call 519-267-4200 or book online.
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