What Does the Tire Pressure Light Mean?

The tire pressure light means your TPMS system has detected a problem. It is almost always one of two things: a tire that is genuinely low on air, or a TPMS sensor that has died. Check your pressures first, because that is the fix that costs nothing.

TPMS stands for Tire Pressure Monitoring System. Every sensor sits inside a wheel, reads the pressure in that tire, and reports it to the vehicle. When one of them reports low, or stops reporting at all, the light comes on.

Why is my tire pressure light on?

Two causes account for nearly everything we see. Either one tire is actually low on air, or a sensor's internal battery has died and it has stopped transmitting. A third, less common cause is a sensor that was physically damaged during a tire change and is now broken or loose inside the wheel.

When a car comes into our shop with the TPMS light on, the most common cause by a wide margin is that the sensor itself has died. The battery inside a TPMS sensor is not replaceable, so once it goes the whole sensor has to be replaced. The second thing we see is a sensor that has been snapped off during a careless mount and is sitting loose inside the tire, no longer attached to anything. And sometimes the answer is the simple one, the light is on because one tire is genuinely low on air and needs topping up.

Solid light versus flashing light

This distinction matters and most drivers do not know it.

If it flashes on startup and then stays on, adding air will not fix it. The vehicle is telling you it has lost contact with a sensor.

How do I turn off the tire pressure light?

Set every tire to the pressure listed on the sticker inside your driver's door jamb, including the spare if your vehicle monitors it, then drive a few kilometres. If the light was triggered by low pressure it will clear on its own. If it stays on or flashes, the system has a fault that inflation will not fix.

Do this first, in order

1. Find the recommended pressure on the door jamb sticker, not the number on the tire sidewall
2. Check all four tires cold, before driving, since driving heats the air and inflates the reading
3. Inflate any low tire to spec
4. Drive several kilometres so the system re-reads
5. If the light stays on, book a diagnostic

The number moulded into your tire sidewall is that tire's maximum pressure, not your target. Inflating to the sidewall number overinflates almost every vehicle on the road.

Why does the tire pressure light come on in cold weather?

Air contracts as it cools, so pressure drops when the temperature does. A cold snap overnight can pull enough pressure out of properly inflated tires to trip the light by morning. It is normal, it is not a fault, and topping the tires back up to spec fixes it.

This is why the light shows up across half the city on the first genuinely cold morning of the fall. Nothing is broken. The air in your tires simply took up less space overnight. Check your pressures whenever the weather turns sharply colder, and again after your winter tires go on.

What does it cost to fix a TPMS sensor?

A diagnostic is $60, and we waive it entirely if you book the repair the same day. A relearn on its own is $20. Supply and install of a new sensor is $50 for small and medium vehicles and $70 for large, large plus, and heavy. If you supply your own sensor, install is 25% of retail.

Posted TPMS pricing

Prices are pre-tax. The diagnostic exists because guessing at a TPMS fault wastes your money. We find out which sensor is dead before anyone buys a part.

Do I need a TPMS relearn after a tire change?

On many vehicles, yes. A relearn teaches the vehicle which sensor is in which corner. It is required after a sensor is replaced, and on some vehicles after a seasonal changeover or a rotation moves the sensors around. Without it, the vehicle reports the wrong tire or nothing at all.

If you run a second set of wheels for winter with their own sensors in them, your vehicle has to learn that set too. Some vehicles do this automatically after a few kilometres of driving. Others need the procedure run with a tool. We handle it either way as part of the changeover.

Key takeaways

• A solid light usually means low pressure. A light that flashes then stays solid usually means a dead sensor.
• Check pressures against the door jamb sticker, not the number on the tire sidewall.
• TPMS sensor batteries are sealed and cannot be replaced. When the battery dies, the sensor is replaced.
• Cold weather drops tire pressure and trips the light. It is normal, not a fault.
• Diagnostic is $60 and waived if you book the repair same day.
• Some vehicles need a relearn after a seasonal changeover or a rotation.

Frequently asked questions

Can I drive with the tire pressure light on? Only far enough to check your pressures safely. The light means the system thinks a tire is low, and driving on an underinflated tire builds heat, ruins the tire from the inside, and hurts your braking. Get to a gas station or a shop, check all four, and go from there.

Can a TPMS sensor battery be replaced? No. The battery is sealed inside the sensor body and cannot be changed, so when it dies the whole sensor gets replaced. TPMS sensors typically last several years before the battery goes. We supply and install a new sensor for $50 on small and medium vehicles and $70 on large ones.

Why does my tire pressure light come on when it gets cold? Air contracts as temperature drops, so pressure falls with it. A sharp overnight cold snap can pull enough pressure out of a correctly inflated tire to trip the light. Top the tires back up to the pressure on your door jamb sticker and the light usually clears once you drive.

What is a TPMS relearn? It is the procedure that teaches your vehicle to recognise its sensors and their positions. It is needed after a sensor is replaced, and on some vehicles after tires are rotated or swapped seasonally. We charge $20 for a relearn on its own.