Why Is My Tire Pressure Light On?
- Tyler Ellis
- Oct 6, 2025
- 3 min read
That little horseshoe-shaped light with an exclamation point (TPMS) is your car’s way of saying one or more tires aren’t at the pressure it expects. If you’re asking “Why Is My Tire Pressure Light On?”, it could be a simple temperature change… or it could be a puncture that’s slowly turning your tire into a sad, underinflated pancake.
At Round Rock Auto Center, we can check the tires, find leaks fast, and reset/calibrate the system correctly so you’re not guessing.
Why Is My Tire Pressure Light On?
Most TPMS lights come from one of these scenarios:
A tire is actually low (most common)
A small leak/puncture is slowly dropping pressure
Weather changed and the pressure dropped naturally
A TPMS sensor is failing or needs relearn after service
Spare tire is low (some vehicles monitor the spare)
If you’ve been wondering why is my tire pressure light on, the first step is always the same: check actual pressures with a gauge and compare to the driver door-jamb sticker—not the number molded into the tire.
What Causes This Problem?
1) Temperature drop (very common)
Air pressure drops roughly 1 PSI for every ~10°F temperature decrease. That means a tire that was “fine” last week can trigger the light after a cold front—without any puncture at all.
2) Nail/screw puncture or slow leak
Small punctures often leak slowly. You might not notice the tire looks low until it’s significantly down.
3) Leaking valve stem or valve core
A loose core or cracked rubber stem can leak, especially after years of heat exposure.
4) Bead leak (rim-to-tire seal leak)
Corrosion on the wheel bead surface can let air seep out gradually. You’ll often see this on older wheels or vehicles that sit.
5) TPMS sensor battery failure
TPMS sensors have internal batteries that typically last years. When they weaken, the system can trigger a warning and may blink before going solid.
6) After tire service (needs relearn)
After rotation, replacement, or sensor work, some vehicles need a relearn so the system knows which sensor is at which corner.
7) Overinflation or mismatched pressures
Yes—sometimes the light comes on because one tire is much higher/lower than the others, even if none look “flat.”
How to Fix It?
Quick checks you can do right now
Check tire pressures cold (before driving) with a gauge.
Inflate all tires to the door-jamb PSI spec.
Look and listen for obvious punctures, screws, or hissing.
If you recently filled tires at a gas station, verify you didn’t accidentally set one tire far off from the rest.
If the light stays on after correcting pressures, it likely needs a TPMS reset/relearn or you have a continuing leak.
If you want a pro-level check quickly, schedule it with Round Rock Auto Center.
How we diagnose it at the shop
Pressure verification on all tires (and spare if monitored) against OEM spec.
Leak check (spray test + inspection for punctures, bead leaks, valve stem leaks).
Repair or replace as needed (patch/plug where safe and allowed, valve service, bead reseal, tire replacement if required).
TPMS scan: read live sensor data, confirm each sensor is transmitting correctly.
Relearn/reset so the system tracks the correct tire positions.
Final drive verification to confirm the light stays off.
Why Act Now
Low pressure kills tires fast. It causes heat buildup and sidewall damage.
It affects braking and handling. Especially in rain or emergency stops.
Fuel economy drops. Underinflated tires increase rolling resistance.
A slow leak can become a blowout. Especially at highway speeds.
If you’re still asking “Why Is My Tire Pressure Light On?”, treat it like an early warning system doing you a favor.
Get Your TPMS Light Off the Right Way
Instead of topping off and hoping, let us find the exact cause—puncture, bead leak, valve issue, or sensor failure—and fix it correctly. Contact Round Rock Auto Center to schedule a tire and TPMS inspection today.
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