Tire Pressure Light On but Tire Inflated

If your tire pressure light is on but your tires appear properly inflated, the issue could be due to temperature changes, a faulty TPMS sensor, or a need for system recalibration after tire maintenance. It’s important to check the tire pressure manually and, if necessary, have the system inspected by a mechanic.

When the tire pressure warning light illuminates on the dashboard, it often triggers an immediate sense of concern. Naturally, you’d assume that one or more of your tires must be low on air. However, what happens when you inspect your tires and discover that they appear perfectly fine, properly inflated, and not at risk of a flat? This scenario is surprisingly common and can be attributed to several factors, not just underinflated tires.

In this post, we’ll explore the various reasons why your tire pressure light may come on despite your tires being adequately inflated, and what you can do to address the issue.

What is the Tire Pressure Monitoring System (TPMS)?

TPMS is a safety feature mandated by law in many countries, particularly after the TREAD Act was passed in the United States in 2000, following numerous vehicle accidents related to underinflated tires.

The primary function of the TPMS is to continuously monitor the air pressure in your tires and alert you when one or more tires fall below a safe threshold, typically around 25% below the manufacturer’s recommended pressure. There are two main types of TPMS systems:

1. Direct TPMS: Uses pressure sensors installed inside each tire. These sensors measure the actual pressure inside the tire and send this data to the vehicle’s onboard computer.
2. Indirect TPMS: Relies on the car’s Anti-lock Braking System (ABS) wheel speed sensors to measure the rotational speed of the tires. A tire with lower pressure rotates faster than a fully inflated tire, triggering the TPMS warning.

Now that we understand how TPMS works, let’s explore why your tire pressure light might come on even though your tires appear to be properly inflated.

Why Does Tire Pressure Light On but Tire Inflated

If the tire pressure light is on, but your tires appear to be properly inflated, there could be several possible reasons for this issue:

Temperature Changes

Tire pressure can fluctuate with changes in the ambient temperature, which can trigger the TPMS light even when the tires are properly inflated. For every 10°F (about 5°C) change in temperature, tire pressure can change by approximately 1 PSI (pounds per square inch).

For example, if you inflate the tires on a warm day, and the temperature drops overnight, the decrease in air pressure caused by the cooler air may be enough to set off the TPMS light. Conversely, when temperatures rise, the pressure may increase again, causing the light to go off.

Solution

Check and adjust your tire pressure regularly, especially during significant temperature swings between day and night, or between seasons. Always ensure that your tires are inflated to the manufacturer’s recommended PSI levels, found in the owner’s manual or on the door jamb sticker.

Sensor Issues or Malfunction

Another common cause of a false TPMS warning light is a faulty or malfunctioning pressure sensor. Over time, the sensors inside your tires (for direct TPMS) can wear out, especially if they are exposed to harsh driving conditions or extreme temperatures. Additionally, the sensors are battery-powered, and as the batteries age, they can become less accurate.

Solution

If you suspect a sensor issue, have your TPMS system inspected by a qualified technician. Depending on the cause of the malfunction, you may need to replace one or more sensors. Regular TPMS sensor maintenance can help prevent these issues in the future.

Recent Tire Rotation or Replacement

If you recently had your tires rotated, replaced, or serviced, the TPMS system may need recalibration. Some vehicles require manual resetting of the TPMS system after tire maintenance, while others will automatically recalibrate after driving for a short period.

In vehicles equipped with indirect TPMS, a tire rotation could confuse the system since the sensors rely on wheel speed. The new tire positions might register differently in terms of rotational speed, especially if there are slight differences in tread wear between the front and rear tires.

Solution

After tire rotation or replacement, consult your owner’s manual to determine whether the TPMS needs to be reset. If required, follow how to reset TPMS after tire rotation or visit a mechanic to recalibrate the system.

Interference from External Factors

Radio frequency interference from external sources can also affect TPMS performance. Devices like mobile phones, two-way radios, or other wireless communication systems can interfere with the signals sent from the tire sensors to the vehicle’s onboard computer, potentially causing the tire pressure light to illuminate incorrectly.

Solution

If you suspect interference is the issue, move away from areas with strong radio frequencies or electronic interference and see if the light turns off. If this occurs frequently, consult a technician to determine if your vehicle’s sensors are more susceptible to interference than they should be.

Damaged or Leaking Valve Stems

Valve stems, which allow air to be added to the tire, can become damaged or corroded, leading to a slow leak that might not be immediately visible. Even if your tires appear inflated, a slow leak can eventually lower the pressure below the recommended level, causing the TPMS light to come on.

Solution

Inspect your valve stems for damage or corrosion, particularly if your tires are older. A mechanic can replace the valve stem if necessary, and this is generally a quick and inexpensive fix.

Low Spare Tire Pressure

Some vehicles include the spare tire in the TPMS monitoring system, especially if it’s a full-sized spare. If your spare tire is low on air, it could cause the TPMS light to illuminate even if your other tires are correctly inflated.

Solution

Check the air pressure in your spare tire and ensure it meets the manufacturer’s specifications. If the spare tire is low, inflating it to the correct PSI should resolve the issue.

Battery Issues in TPMS Sensors

For vehicles with direct TPMS, each tire sensor is powered by a small battery. Over time, these batteries can wear out, and as they do, the sensor may send inaccurate information to the car’s computer. When the battery starts to fail, the TPMS light can activate even if the tire pressure is correct.

Solution

TPMS batteries generally last around 5 to 10 years, depending on use. If the batteries are low, you’ll need to replace the sensors entirely, as the batteries are not replaceable separately. A professional mechanic can handle this task.

How to Reset the Tire Pressure Monitoring System

In some cases, you may need to manually reset the TPMS after resolving the underlying issue, especially if the light remains on even after you’ve confirmed that the tire pressure is correct. Here’s a general guideline for resetting the Low tire light.

Always refer to the owner’s manual for specific instructions, as the reset procedure can vary by make and model.

Frequently Asked Questions

Here are some FAQs about tire pressure light on but tire inflated –

1. Can I drive with the tire pressure light on if the tires are properly inflated?

While it may be safe to drive short distances with the TPMS light on if you’ve confirmed the tire pressures are correct, you should still have the system checked. A malfunctioning TPMS can’t alert you to actual pressure issues that might arise later.

2. What should I do if the TPMS light flashes and then stays on?

A flashing TPMS light often indicates a problem with the sensors, such as a low battery or a malfunction. If the light flashes for about 60 to 90 seconds before staying on, it’s best to have the system checked by a mechanic.

3. How often should I check my tire pressure?

You should check the tire pressure at least once a month and before long trips. Tire pressure fluctuates with temperature changes, so checking it regularly ensures safe driving conditions.

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

Cold weather causes the air in your tires to contract, which can lower the tire pressure and trigger the TPMS light. This is a common occurrence during seasonal changes.

5. How much does it cost to replace a TPMS sensor?

Replacing a TPMS sensor can cost anywhere from $50 to $200 per sensor, depending on your vehicle’s make and model. Labor costs for installation can vary as well, so check with your local mechanic for a specific quote.

Conclusion

If your tire pressure light is on but your tires appear to be properly inflated, don’t ignore the issue. While it may not signal an immediate safety hazard, it could indicate underlying problems with the TPMS or tires themselves. By understanding the causes and knowing how to address them, you can ensure your vehicle remains safe and your TPMS continues to function correctly.