Why Is My TPMS Light on, but the Tires Are Fine?
Your vehicle has many sensors and technologies on board to cruise safely on the highways while spending energy efficiently.
One of the technologies fitted to your vehicles is the tire pressure monitoring system (TPMS). It monitors your tire pressure and alerts you to risky pressure levels in your tires.
However, the TPMS light on your dashboard can illuminate to signify underinflated tires when a quick check reveals the tires have the correct amount of pressure. This scenario can surprise you and make you doubt the reliability of the sensors. We’ll cover reasons why the TPMS light might be unreliable sometimes.
How the Tire Pressure Monitoring System Works
The TPMS is a safety feature in all vehicles manufactured now. It is designed to constantly check your tire pressure. Having the correct air pressure in your tires is safe and also reduces the cost of transport.
The Safety of TPMS
The TPMS works to improve your safety while cruising on highways in your vehicle. It usually alerts you to underinflated tires. You want to ensure your tires are properly inflated because low tire pressure reduces the handling of your vehicle and causes safety concerns.
At the same time, low pressure increases the chances of a tire burst. The low tire pressure will increase friction between your tire and the asphalt, weakening the tire structure. As a result, you may suffer a tire burst which can spell disaster if you were cruising at a high speed.
The Fuel Efficiency of TPMS
Many people don’t think their tire pressure matters. However, it matters if you want to spend less money on gas (or charging) and travel safely. Low tire pressure results in the vehicle spending more energy than necessary since the underinflated tire causes a lot of rolling resistance.
There are two types of TPMS fitted on vehicles to improve their fuel efficiency and most importantly, safety while on major highways:
Direct TPMS
This system relies on air pressure sensors inside your tires to determine whether your tires are correctly inflated. Each wheel has an air pressure sensor attached to the valve stem or banded to the wheel.
The sensors transmit air pressure data wirelessly to your vehicle’s onboard computer, which displays it on the dashboard. If one of the wheels has incorrect air pressure, you’ll see the TPMS light illuminate in your dashboard.
Indirect TPMS
This system uses the sensors of your vehicle’s Anti-lock Braking System (ABS) to detect low tire pressure. Low tire pressure reduces the diameter of your wheel. As a result, the wheel spins faster to cover the same distance as the other wheels.
This system detects the speed of the wheel(s) spinning faster than the rest and alerts you to a potential low tire pressure in a particular wheel.
Common Reasons for TPMS Light Activation
Sometimes, the TPMS light illuminates your dashboard when every tire has the correct pressure inside. There are a few reasons why the TPMS light can give a false alarm:
Temperature Fluctuations
Air pressure changes with temperature. If the asphalt or road surface is hot, heat warms up the air in your tires, resulting in air expansion. Your tires will inflate more, leading to TPMS giving false excess air pressure.
Conversely, cold temperatures cause the air in your tire to contract, causing the TPMS to register falsely low tire pressure.
Sensor Issues
What’s more, your TPMS light can illuminate because of a malfunctioning sensor. A faulty sensor might interpret normal tire pressure as low or high tire pressure and send that information to the TPMS light.
System Calibration Problems
Vehicles with an indirect TPMS are likely to experience false alarms because of this issue. Indirect TPMS relies on a baseline measurement used as a reference for normal rotation at the right air pressure.
The Baseline Measurement is set during tire changes or replacement. If it was set with incorrect tire pressure, the indirect TPMS system would give false alarms if you correctly inflate your tires because the baseline was not properly set.
Pressure Threshold Sensitivity
Your vehicle manufacturer has set a specific tire pressure below which your TPMS light will illuminate. This set tire pressure threshold is usually 25% below the recommended pressure in your tires.
However, some vehicles have the pressure threshold set sensitively and cause alarms with minor tire pressure changes.
Interference or Malfunction
Your dashboard has sophisticated electronics working to make the vehicle a safe and efficient traveling machine. If an electronic component malfunctions, it can cause the TPMS light to illuminate falsely.
Steps to Diagnose and Address the Issue
If you can't rely on your TPMS light, you can take a few steps to ensure your tire pressure is accurate.
Visual Inspection of Tires
Check the shape of the tires for any bulging sidewall since this can indicate underinflated tires. You’ll also check if the tire’s contact patch is flat, as it can indicate low tire pressure.
Uneven tread wear can also indicate improperly inflated tires. If you notice any of these signs, it could mean your tires need more air pressure.
Manual Pressure Check
A tire pressure gauge measures the air pressure inside your tires. Unscrew the cap on your valve stem and firmly press the tire pressure gauge onto the stem to establish a tight seal.
Then compare the recorded air pressure with the recommended tire pressure in your vehicle model’s owner’s manual.
Resetting the TPMS Light
You can use general methods to reset your TPMS light if it is unreliable. Some vehicles have a TPMS reset button under the steering wheel. You’ll turn the key in the ignition to the “On” position without starting the engine and press this button to reset the TPMS light.
Once the TPMS light blinks 3 times, start the engine but wait 20 minutes before driving away; this gives the TPMS time to reset. You can also over-inflate all tires by 3 PSI and deflate them completely before pumping in the air to the recommended pressure. This can reset the sensors and correct any false TPMS light.
Seeking Professional Help
It’s important to know that each vehicle brand has specific procedures for correcting any false TPMS light. If the general methods don’t work, you’ll seek the help of a professional mechanic.
Preventing False TPMS Alerts
Your vehicle’s TPMS light can be unreliable due to various factors. You can prevent any unreliability through the following means:
Regular Tire Maintenance
Proper tire mounting can eliminate false TPMS lights. You’ll mount your tires and correctly position the sensors to ensure the sensors accurately monitor the tire pressure. Rotating your tires regularly to check for uneven wear ensures your tires are in good condition to rotate as per the set baseline measurement.
This will ensure the Indirect TPMS works correctly and prevent incorrect TPMS lights. You can also recalibrate the TPMS system after rotating or replacing your tires to prevent false alarms.
Monitoring Weather Impacts
Tire pressure decreases in cold weather conditions because cold reduces air's intermolecular distance. You’ll pump in more air to compensate for the contraction of air and resolve a false TPMS light.
However, hot temperatures increase intermolecular distances, causing air pressure to increase. Letting out some air can reduce air pressure in your tires and prevent sensors from detecting excess pressure.
Keeping TPMS Components in Good Condition
Air pressure sensors can be faulty or malfunction. This can cause the TPMS light to illuminate when there’s no cause for alarm. You can prevent false light from illuminating your dashboard by keeping your sensors working efficiently.
Additionally, you can replace any electronic in your dashboard that’s not working correctly. However, keeping these components working correctly requires the help of a professional mechanic if you don’t have a background in vehicle maintenance.
When to Be Concerned about TPMS Light
Even though the TPMS light might give a false alarm, it might be concerning if it persistently lights up on your dashboard. The TPMS light will be steady if one or more tires have a significantly low pressure below the recommended tire pressure.
If your tire pressure is constantly 25% below the recommended pressure, it will pose a danger on the highways when cruising at higher speeds. Besides your low tire pressure reducing fuel efficiency, it reduces the wheel traction, which impacts handling.
Frequent On/Off Cycling
Sometimes, your TPMS light illuminates one minute and goes off the next. This frequent on/off of TPMS light can be the result of temperature effects. Your tire pressure will change as the road surface temperature changes.
Your TPMS light will then give off a false light. This scenario usually corrects itself if the temperature goes back to normal. However, if your vehicle persistently shows the on/off TPMS light, it could be a signal for an underlying issue.
Maybe your tires are leaking air slowly, or the sensors might be malfunctioning. Either way, you will need to address this issue.
Initial TPMS Flashing Light
The TPMS light can be a flashlight for 60 to 90 minutes when you start the engine, and then the light stays on. This could be a sign of a malfunctioning sensor. Your air pressure sensor could not be functioning inefficiently if it behaves this way.
You can’t rely on a malfunctioning sensor to accurately report a wheel with improper tire pressure. Therefore, you’ll need to take your vehicle for diagnostics to detect the underlying issue.
Consistent Low-Pressure Detection
At the same time, you want to be concerned about your TPMS light if it constantly alerts you to low tire pressure. If a manual tire check reveals low pressure despite regular inflation, your tire is leaking.
Air could be slowly leaking from the valve stem. A slow puncture can be the culprit. You’ll take your vehicle for a tire repair to solve the TPMS light.
Tip: What to do if the TPMS light accompanies other system alerts
The TPMS light can illuminate your dashboard along with other dashboard lights. You should solve more critical issues first, such as the engine light, brake system light, and tire pressure light.
Conclusion
Your vehicle has tire pressure monitoring sensors to improve your vehicular safety and increase fuel efficiency. However, the sensors might display inaccurate signals because of several issues. You can do manual checks on the tire to correct false TPMS lights.