An aftermarket catalytic converter costs roughly €200-600 fitted, the original can exceed €1,500 on some models. Before replacing it, though, check it is really the converter at fault: code P0420 alone is not enough.
Indicative prices
| Option | Cost fitted | Notes |
|---|---|---|
| Approved aftermarket catalytic converter | €200-600 | Legitimate and much cheaper, if approved |
| Original catalytic converter | €600-1,500 and over | Some premium cars exceed this |
| Rear lambda sensor | €100-250 | Frequent cause of P0420, costs far less |
Code P0420 is not enough
The catalyst efficiency below threshold error (P0420) can depend on:
- Slow or faulty rear lambda sensor (much cheaper)
- Exhaust leaks before or between the sensors
- Prolonged rich mixture from injectors or MAF
- Oil consumption poisoning the converter
Replacing the converter without ruling these out often means getting the same error a few weeks later, with a new part already compromised.
How it is checked before spending
- Comparison of the two lambda sensor signals in real time
- Exhaust back-pressure measurement if blockage is suspected
- Exhaust leak test
- Reading of fuel trims
Original or aftermarket
A quality aftermarket part with valid approval is a legitimate and much cheaper choice. Beware of unapproved products: besides not being allowed, they often bring the error back through insufficient efficiency. Check the approval marking and ask for the supplier’s paperwork.
How MasterTuning helps
We read the real values of the control unit, not just the code: that is the difference between finding the faulty component and replacing parts by trial and error. After the repair we clear the error and check that it does not come back. Find the nearest centre or contact us.
Want a tailored quote? Book a diagnosis at the nearest MasterTuning centre.
Frequently asked questions
How much does it cost to change the catalytic converter?
Roughly €200-600 with an approved aftermarket part; the original can exceed €1,500 on some models.
Does P0420 mean the converter has to be replaced?
Not necessarily: it can be the rear lambda sensor, exhaust leaks or a rich mixture. They must be ruled out first.
Is an aftermarket converter fine?
Yes if it is approved and good quality. Unapproved products are not allowed and often bring the error back.
How long does a catalytic converter last?
If the engine is in order it can exceed 200,000 km; a rich mixture and oil consumption shorten its life a lot.
