What is a TPMS Sensor?
A battery-powered sensor inside each wheel that radios its tyre pressure to the dashboard.
Simplified animation — not to scale.
In plain English
A small radio transmitter mounted to the inside of each wheel (usually built into the valve stem) that measures the air pressure and temperature inside the tyre and sends the reading wirelessly to the car's TPMS receiver.
"Like a fitness tracker for each tyre — it wakes up, takes a reading, then radios it to the car so the dash knows the moment one is going flat."
How it works
Each sensor contains a pressure-sensing membrane, a temperature sensor and a tiny radio. Every few seconds — or whenever pressure changes suddenly — it wakes up, takes a reading and broadcasts a unique ID plus the value to a receiver in the car. The ECU compares each wheel against a low-pressure threshold (typically around 25% below placard pressure) and lights the TPMS warning if any wheel is too low. Sensors are battery-powered and typically last 5–10 years before needing replacement.
Signs of trouble
- ⚠TPMS warning light stays on after inflating tyres
- ⚠TPMS light flashes for 60–90 seconds at startup
- ⚠One wheel consistently reads no value
- ⚠Light returns shortly after a tyre change
£40–£100 per wheel
Always get a written quote. Prices vary by car, region, and parts brand.