Cause
Failed catalytic converter
A converter that has lost efficiency, melted or broken up internally. It is the most expensive answer and the least often correct one — a converter does not wear out on its own, it is killed by what reaches it, so an engine running rich, burning oil or misfiring is the reason and will kill the replacement too.
A blocked converter also strangles the engine, which shows as a car with no power at all rather than an emissions fault.
Typically specialist work. Needs equipment or training most home workshops do not have.
Codes this can cause (12)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0420 Catalyst System Efficiency Below Threshold — Bank 1 Likely for this code Moderate
- P0421 Catalyst 1 Efficiency Below Threshold Bank 1 Likely for this code Moderate
- P0422 Catalyst 2 Efficiency Below Threshold Bank 1 Likely for this code Moderate
- P0423 Heated Catalyst Efficiency Below Threshold — Bank 1 Likely for this code Moderate
- P0430 Catalyst System Efficiency Below Threshold — Bank 2 Likely for this code Moderate
- P0431 Catalyst 1 Efficiency Below Threshold Bank 2 Likely for this code Moderate
- P0432 Catalyst 2 Efficiency Below Threshold Bank 2 Likely for this code Moderate
- P0433 Heated Catalyst Efficiency Below Threshold — Bank 2 Likely for this code Moderate
- P2074 Manifold Absolute Pressure/Mass Air Flow — Throttle Position Correlation at Higher Load Moderate
- P2096 Post Catalyst Fuel Trim System Too Lean — Bank 1 Moderate
- P2098 Post Catalyst Fuel Trim System Too Lean — Bank 2 Moderate
- P2379 O2 Sensor Out of Range During Deceleration Bank 2 Sensor 2 Moderate
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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