Why did my TPMS light come on?
Usually, it means one or more tires are underinflated or there’s a fault in the Tire Pressure Monitoring System (TPMS). Start by checking the tire pressures and inspecting the tires, then address any issues or seek service if the alert persists.
What TPMS is and how it works
TPMS stands for Tire Pressure Monitoring System. It protects you from driving on underinflated tires by warning when pressure falls below a manufacturer-specified threshold. There are two main types: direct TPMS, which uses sensors in each tire to read pressure, and indirect TPMS, which estimates pressure differences using wheel speed sensors. The exact warning threshold varies by vehicle, and readings can be influenced by temperature and driving conditions. Some tires or tire services also require a reset or relearn to recalibrate the system after work.
Direct vs indirect TPMS
Direct TPMS measures actual air pressure with sensor valves in each tire and reports the data to the car’s computer. Indirect TPMS does not measure pressure directly; it compares wheel rotations to infer pressure differences. Both systems aim to alert you before a tire becomes dangerously underinflated, but their behavior and reset requirements can differ across makes and models.
Common reasons your TPMS light is on
Here are the typical causes behind a TPMS warning:
- One or more tires are underinflated relative to the recommended pressure.
- Temperature changes cause tires to lose or gain a few pounds of air, triggering a warning.
- A tire has a slow leak or puncture that lowers pressure over time.
- A TPMS sensor or its battery is damaged or dying, causing a fault in the system.
- You recently rotated or replaced tires, or changed tire sizes, which may require a relearn or calibration.
- The TPMS itself is malfunctioning or requires service beyond simple inflation correction.
In general, underinflation and sensor or calibration issues are the most common culprits. If the light goes out after inflating to the correct pressure, you’ve likely resolved a simple issue; if it stays on, further inspection is advisable.
What to do when the TPMS light is on
Follow these steps to diagnose and address the warning safely:
- Check the tire pressures on all four tires (and the spare if your vehicle uses one with a sensor) with a reliable gauge.
- Inflate each tire to the vehicle’s recommended cold-inflation pressure, found on the door jamb placard or in the owner’s manual.
- Drive the vehicle for a short period (often 5–10 minutes at a moderate speed) to allow the system to update after inflation.
- Inspect tires for visible damage, nails, cuts, or slow leaks and repair or replace as needed.
- If the light remains on after proper inflation and a short drive, consult your owner's manual for the recommended TPMS reset/relearn procedure or visit a tire shop or dealership for a diagnostic scan.
- If the TPMS light is flashing, treat it as a potential system fault and seek service promptly.
- After any service or relearn, verify the warning has disappeared by driving and checking that the light stays off.
After maintenance, most drivers should see the light turn off on its own or after the relearn procedure is completed. If you recently gained new tires or made changes to the TPMS setup, a professional check can prevent recurring warnings.
Summary
The TPMS light is a safety feature meant to alert you to potential tire pressure issues or system faults. Most often, it signals underinflation, but it can also point to sensor problems or the need for a system relearn after tire work. Regularly check tire pressures, inspect for damage, and seek professional service if the warning persists or progresses (such as a flashing light).
