What does code P0420 mean?
The catalytic converter on bank 1 is no longer operating at the minimum efficiency required to reduce exhaust emissions.
OBD-II Code
P0420 — Catalyst System Efficiency Below Threshold (Bank 1
The catalytic converter on bank 1 is no longer operating at the minimum efficiency required to reduce exhaust emissions.
Common symptoms
- Sulfur smell from exhaust
- increased fuel consumption
- persistent check engine light
Possible causes
- Degraded catalytic converter
- slow or faulty oxygen sensors
- exhaust leaks
Initial recommendation
Check oxygen sensor operation, inspect exhaust system for leaks, evaluate catalytic converter condition.
Safety notice
This information is for guidance only and does not replace a physical vehicle inspection or diagnosis by a qualified mechanic. If the vehicle has severe power loss, smoke, a fuel odor, overheating, brake or steering problems, or any unsafe behavior, avoid driving it and seek professional inspection.
Analyze this code with MecaOBD
Use the app to combine code P0420 with your vehicle's actual symptoms for more complete diagnostic guidance.
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