Error code P0420: Catalyst efficiency below threshold
The code P0420 indicates that your vehicle's catalytic converter isn't working with the expected efficiency. It's one of the most common codes in both diesel and petrol cars, and can have multiple causes. We'll explain everything you need to know.
What exactly does P0420 mean?
Your car's OBD-II system constantly monitors the catalytic converter's efficiency by comparing readings from the lambda sensors before and after the converter. When it detects that the conversion of polluting gases is below the set threshold, it generates the P0420 code.
Main causes
Catalytic converter worn out or deteriorated due to age (over 150,000 km), defective rear lambda sensor giving incorrect readings, exhaust leak before the catalytic converter, incorrect fuel mixture damaging the catalytic converter, use of low-quality fuel, burnt oil contaminating the catalytic converter, or a previous injector failure that wasn't repaired in time.
Associated symptoms
Check engine light on, noticeable loss of power, rotten egg smell from the exhaust (sulfur), increased fuel consumption, ITV failure due to emissions, and in some cases, metallic noises from the catalytic converter.
Cost of the repair
If the cause is a faulty lambda sensor, the repair is relatively economical (80?-200?). If the catalytic converter needs replacing, the cost is higher, but at Zamule Cars we offer approved alternatives at much more competitive prices than the dealership.
Diagnostics at Zamule Cars
At Zamule Cars We perform a complete diagnostic to identify the exact cause before providing a quote. We never replace parts unnecessarily. No appointment needed in Son Castell, Palma. 971 918 147.
Need a trustworthy workshop?
If you need a reliable workshop in Palma de Mallorca, at Zamule Cars We specialize in electromechanics, diagnostics, and comprehensive maintenance. We offer no-obligation advice.
Write us on WhatsApp | Tel: 682 931 164
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