Converts carbon monoxide, unburnt hydrocarbons and oxides of nitrogen into carbon dioxide, water and nitrogen, using a precious-metal coating on a ceramic honeycomb. Its efficiency is never measured directly: the module compares the upstream and downstream oxygen sensors and infers how much oxygen the converter is still able to store and release. That inference is only as good as both sensors and the pipe between them, which is why an efficiency code is so often an exhaust leak or an aged rear sensor rather than a failed converter. When a converter genuinely has failed, something else destroyed it — a misfire, prolonged rich running, or oil and coolant consumption poisoning the substrate — and fitting a new one without finding that cause destroys the replacement too.
Also known as: cat, catalyst, converter, cat converter, three way catalyst, twc, warm up catalyst, main catalyst, close coupled catalyst, pre cat, underfloor catalyst
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A catalytic converter is a ceramic honeycomb, coated with precious metals, sitting in the exhaust. Gas passes through it and comes out chemically different. There are no moving par...
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