Exhaust & emissions · Sant Andreu
Catalytic converters: diagnosis and replacement
Catalyst efficiency error, sulphur smell, a rattle under the car or an ITV emissions failure. We verify whether the converter is the culprit and replace it with a homologated part.
What does this service include at Tallers Marathon?
Sensor and gas checks to confirm the converter’s condition, and replacement with a unit homologated for your exact engine.
- Data-based diagnosisWe compare the lambda sensors before and after the converter.
- Other causes ruled outA misfire or a leaking injector can mimic (and cause) the fault.
- Homologated partA converter homologated for your exact engine variant.
- Final gas checkEmissions verified correct after fitting.
How do I know the catalytic converter is bad?
Typical signs: an efficiency error (P0420/P0430), a rotten-egg smell, power loss from blockage, or a rattle if the internal monolith has broken up. Confirmed by comparing lambda sensor signals and measuring gases.
What almost nobody tells you: the converter is the victim, not the criminal. It dies poisoned by an engine burning oil, drowned by a leaking injector, or melted by misfires sending raw fuel down the exhaust. Fitting a new converter without fixing the cause condemns it to die the same way within months — and they are expensive parts. That is why our protocol always includes diagnosing the cause: sometimes the solution starts with a lambda sensor or the injection system, not the converter.
Frequently asked questions
Are cheap unbranded converters any good?
Non-homologated or poor-quality units never reach the required efficiency: the error returns and the ITV fails. We fit parts homologated for your engine.
Can a converter be cleaned?
Sometimes, if the blockage is deposits; if the monolith is melted or broken, replacement is the only option.
Why was my converter stolen?
They contain precious metals and some models are theft targets. If the car starts sounding like a motorbike, check underneath; we also fit anti-theft guards for vulnerable models.
Can the P0420 code be something else?
Yes: aged sensors, exhaust leaks or incorrect mixture give the same code. That is why we measure before quoting for the converter.
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