Catalytic converter replacement cost UK (2026): don’t replace it from P0420 alone
Updated 23 July 2026 · OBDCode UK editorial
Typical UK fitted prices in 2026
| Work | Typical price |
|---|---|
| Aftermarket underfloor catalyst fitted | £250–£600 |
| Manifold-integrated catalyst | £500–£1,200+ |
| Lambda sensor, each | £120–£250 |
| Theft-related exhaust/underbody repair | £300–£1,500+ |
These are planning ranges, not quotes. Confirm whether VAT, diagnosis, fluids, calibration and related parts are included.
What changes the price?
- Location/count: a car may have pre-cats and underfloor catalysts.
- Approval and quality: the cheapest part may not meet durability or type-approval needs.
- Root cause: misfire, oil burning or rich fuelling can destroy the replacement.
- Sensors and corrosion: seized lambda sensors/fasteners add labour.
Confirm the fault before authorising the job
Read P0420 freeze frame, check for exhaust leaks and misfire/fuel-trim faults, then assess upstream/downstream oxygen-sensor behaviour. Do not fit a catalyst while the engine is still damaging it.
How to compare quotes like-for-like
Confirm exact catalyst position, approval/brand, lambda sensors, gaskets, seized-fixing contingency, VAT and warranty. Ask what testing showed the converter—not a leak or sensor—failed.
- Topdon OBD2 scannersTopdon diagnostic scanners with full-system readouts
- XTOOL diagnostic toolsXTOOL code readers for petrol and diesel cars
- Autel UK testersAutel professional-grade diagnostic testers
Frequently asked questions
Can I drive with P0420?
The car may drive normally, but emissions can be high and an underlying misfire or rich condition can cause more damage. Diagnose promptly.
Will a new oxygen sensor fix P0420?
Only if testing proves its signal or heater is faulty. Replacing sensors without checking leaks, fuel control and catalyst behaviour is guesswork.
Sources and further reading
General guidance for UK drivers, not professional advice. MOT rules follow the DVSA inspection manual (2026 edition).