What Is TPMS and Why Does It Matter?
Since November 2014, all new cars sold in the UK have been required to be fitted with a Tyre Pressure Monitoring System (TPMS). The system monitors the air pressure in each tyre and alerts the driver via the dashboard warning light when a tyre drops below a safe threshold — typically around 25% below the recommended pressure.
Two Types of TPMS
Direct TPMS uses pressure sensors physically mounted inside each wheel, transmitting real-time pressure data to the vehicle's ECU. This is the more accurate type. Indirect TPMS does not use dedicated sensors — it infers pressure loss by monitoring wheel rotation speeds via the ABS sensors. A deflated tyre rotates faster, triggering the alert.
Why Is My TPMS Warning Light On?
If your TPMS light illuminates, check all four tyre pressures immediately. Common causes include:
- A puncture or slow leak in one or more tyres
- Temperature drop (cold weather causes pressure to drop about 1 PSI per 10°F decrease)
- A faulty or dead TPMS sensor battery (sensors typically last 5–10 years)
- A sensor not reset after a tyre change
TPMS Sensor Replacement
Direct TPMS sensors contain a battery that cannot be replaced — when the battery dies, the whole sensor must be replaced. This is a common requirement when fitting new tyres to vehicles over 5 years old. Saltire Mobile Tyres carries a range of universal and OEM-equivalent TPMS sensors and can replace and recalibrate them as part of your mobile tyre fitting appointment across Yorkshire and Scotland.