The TPMS warning is indicating a system fault rather than a low tyre. On cars first used from 2012 onwards this is a testable item, so a permanently lit TPMS light is a failure even when all four tyres are correctly inflated.
Wording as it commonly appears on an MOT certificate: “Tyre pressure monitoring system inoperative or warning indicating a system malfunction”.
What does it mean?
The TPMS warning is indicating a system fault rather than a low tyre. On cars first used from 2012 onwards this is a testable item, so a permanently lit TPMS light is a failure even when all four tyres are correctly inflated.
How serious is it?
Usually recorded as: Major. The tester assesses the actual vehicle on the day, so your certificate is what counts.
What normally causes it?
- A flat sensor battery — they're sealed units and typically last around seven to ten years
- A sensor damaged during a tyre change
- Sensors not relearned to the car after new wheels or a tyre rotation
- A corroded valve stem on an aluminium-stemmed sensor
What a mechanic would check
Read the TPMS system with a dedicated tool to see which sensor isn't reporting and whether it's transmitting at all. That immediately separates a dead sensor from a car that just needs a relearn — and a relearn costs a fraction of new sensors.
What might need replacing
- One TPMS sensor, or a full set if they're all of an age
- A relearn or reset procedure only
- Valve service kits when tyres are next changed
Can you still drive it?
It's a failure item on affected cars, but the light itself isn't a mechanical danger. The real cost is that you lose the early warning of a slow puncture, so check pressures manually until it's fixed.
Repair cost
A relearn is cheap; sensors are priced per wheel and vary widely between makes. Have the system read before agreeing to a full set — plenty of TPMS lights turn out to be one sensor or a reset.
Before the retest
Check every tyre, not just the one that failed — the legal minimum is 1.6mm across the central three-quarters of the tread, all the way round. Make sure tyres on the same axle match in size and construction, and that all wheel nuts or bolts are present and tight. Set pressures to the figure on the door shoulder or in the handbook the morning of the retest.
Retest rules
If the vehicle stays at the test centre for repair and is retested within 10 working days, a partial retest is often free; some items qualify for a free retest if you bring the car back by the end of the next working day. The exact conditions are set out on GOV.UK, so confirm with the test centre before you leave. A major or dangerous failure means the car cannot legally be driven away unless the previous MOT is still valid and nothing dangerous was recorded — check your certificate first.
Related help
More tyres and wheels failures · MOT failure decoder · Ask a mechanic about your certificate
This is general guidance from a UK mechanic, not a substitute for a physical inspection. Only the tester who inspected your vehicle can confirm what was recorded and why.