A tire pressure monitoring system (TPMS) is your early warning that air pressure has dropped below a safe level. On the first cold mornings in Libertyville, that amber light loves to wake up. You have not hit a nail. The physics of cold air usually does the work.
Here is what is happening, what to do next, and how we help our customers keep the light off all winter.
What Your TPMS Is Actually Measuring
Most vehicles use direct TPMS sensors mounted inside each wheel. They read pressure, report it by radio to the car, and often show individual tire numbers on the dashboard. Some older models use an indirect system that estimates pressure by monitoring wheel speed differences through the ABS system. Either way, the alert means at least one tire is below the threshold set by the manufacturer, not that a sensor has failed.
Why Cold Weather Triggers the Light
Air contracts as the temperature drops. As a rule of thumb, tire pressure changes about 1 psi for every 10°F change in outside temperature. A tire that was sitting happily at 35 psi in the afternoon can read 31 to 32 psi after a 30 to 40 degree overnight swing. That is enough to cross the TPMS threshold and flip the light on during your morning start. As the day warms or the tires heat up on the road, the pressure rises, and the light may go off again. The tire did not fix itself, it is just riding the temperature curve.
How Much Pressure You Actually Need
Use the sticker on the driver’s door jamb, not the sidewall maximum. The placard lists the correct “cold” pressures for your vehicle and load, measured before you drive. In winter, we set the SUVs to the higher “full load” value on the label if you carry passengers, gear, or a roof box, because the extra weight requires more pressure for stability and to control heat at highway speeds.
Common Cold-Morning Scenarios We See
- The light is on at breakfast, then off by lunch. Morning cold dropped the tires below the threshold, the afternoon warmth brought them back.
- The light stays on after a cold snap because one tire was already a little low, and the temperature drop pushed it well under the line.
- The light flickers after a tire rotation or seasonal changeover, which usually means the system needs a reset or relearn so the car knows which sensor is at which corner.
- The light is on, and one wheel reports nothing at all. That often points to a sensor with a weak battery, common around the 7 to 10 year mark.
What To Do When the Light Turns On
- Check pressures with a reliable gauge while the tires are cold.
- Inflate to the placard number, then drive a few miles. Many systems clear after a short drive if pressures are back in range.
- If your vehicle uses an indirect system, perform the reset procedure in the owner’s manual after you set pressures.
- Recheck in a day. If one tire keeps losing a few psi, you may have a slow leak at a nail, valve core, or the bead seat.
When Adding Air Does Not Clear the Light
If the light stays on, you may have one of these issues:
Slow leaks
Small punctures, corroded aluminum valve stems, or bead leaks from winter corrosion. We inspect the tire inside and out, clean the bead seat, and reseal if needed.
TPMS sensor problems
A tired sensor battery, a damaged valve stem, or a sensor that did not wake up after a wheel service. We can test sensor output, replace a single sensor, or preemptively replace a set during tire replacement to avoid multiple trips.
Incorrect reset
After rotations, indirect systems need a recalibration. Direct systems sometimes need a relearn if tire positions were changed or if a sensor was replaced.
Simple Habits That Prevent Winter Warnings
Set pressures on the first truly cold morning of the season, not in a warm garage. Keep a pencil gauge in the glove box and aim to check monthly, plus after every 10 to 15 degree temperature drop.
If you know a deep freeze is coming, add a couple psi up to the placard limit, since you will lose some overnight. Remember that short trips do not warm the tires much, so cold readings will stick around longer.
For vehicles with a full-size spare that carries a sensor, set that pressure too, so the system does not complain later.
Get Professional TPMS and Tire Service in Libertyville, IL, with Pit Shop Auto Repair
If your TPMS light keeps returning, swing by our Libertyville shop. We will set your tires to the correct cold pressures, scan and test each sensor, find slow leaks, and perform the proper reset or relearn so the system behaves. Our team can also replace aging sensors during tire work to save you an extra visit.
Stop in, and leave with a quiet dash, correct pressures, and confident winter traction.
