Tire Pressure Monitoring: What a Warning Can and Cannot Tell You

A tire pressure warning is a reason to check the tires, not a diagnosis of why a light came on. Cold weather, a pressure leak or a monitoring-system fault can all lead to a conversation at the service counter. The first job is to understand the warning and measure the tires.

Here's a practical guide to what tire pressure monitoring systems (TPMS) do, why systems differ, and what to discuss when changing to seasonal wheels.

Start with the tires, not the reset button

If a low-pressure warning appears, inspect the tires and check their pressure as soon as it is safe to do so. Use a reliable gauge and compare the readings with the vehicle manufacturer's recommended cold pressures on the vehicle information label or in the owner's manual. Front and rear recommendations can differ. A seriously underinflated tire should not be driven on; arrange appropriate assistance. Transport Canada explains how to find and check the recommended pressures.

Don't clear a warning before establishing why it appeared. If pressure falls again or visible damage is present, a tire professional should inspect the assembly. A flashing warning followed by a steady light can indicate a monitoring-system malfunction on some vehicles; consult the vehicle manual and arrange a system inspection. NHTSA's tire guidance describes this warning pattern, but the vehicle's instructions remain the right reference for its display.

Direct and indirect systems use different information

Direct TPMS uses pressure sensors mounted in the wheels to measure pressure. Depending on the vehicle, the display may show individual readings or only a warning. Indirect TPMS uses wheel-speed information to identify changes associated with an underinflated tire; it does not directly measure air pressure at each wheel. Transport Canada and Continental describe both approaches.

The distinction matters when preparing a second set of wheels. A direct system may need compatible sensors in that set. An indirect system uses a different sensing approach, so do not assume the same parts or procedure apply. The right answer depends on the vehicle, wheels and manufacturer's instructions.

Ask about TPMS during the seasonal wheel handoff

Before the appointment, record the vehicle year, make and model and ask whether the customer has a second set of wheels. Check what system the vehicle uses and whether the replacement wheels and, where applicable, sensors are compatible. Transport Canada notes that winter-wheel changes may affect system operation if the correct sensors are not installed.

After installation, follow the vehicle and sensor manufacturer's applicable initialization, reset or relearn procedure. These steps are not interchangeable across every vehicle. Confirm what the dashboard shows and explain any outstanding warning to the customer; a light going out alone does not establish that the tires are correctly inflated or that every sensor is healthy.

Keep measuring even when the light is off

Some systems warn only after pressure has fallen substantially. They do not replace regular checks. Transport Canada recommends measuring tire pressures at least monthly, when the tires are cold, including the spare where applicable. Pressure can change as the weather cools, so a warning that disappears after driving still deserves a proper check.

For the next seasonal change, pair the pressure check with a record of wheel positions and condition. Our seasonal tire storage handoff checklist provides a starting point for that conversation.