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Emissions / Exhaust

Tech Tip: Close-Coupled Converter And Engine Replacement

MODELS: 2019 and Prior GM Passenger Cars and Trucks with Close-Coupled Catalytic Converters


Certain 2019 and prior General Motors products may be equipped with a new style of catalytic converter, technically known as the close-coupled catalytic converter, providing quick catalyst warm-up, resulting in lower tail pipe emissions earlier in the operating cycle.

If an engine breakdown or non-function were to occur (such as broken intake/exhaust valve or piston), debris may be deposited in the converter through engine exhaust ports. If the engine is non-functioning due to a severe overheat event, damage to the ceramic “brick” internal to the catalytic converter may occur. This may result in ceramic debris being drawn into the engine through the cylinder head exhaust ports.


If a replacement engine is installed in either of these instances, the replacement engine may fail due to the debris being introduced into the combustion chambers when started. When replacing an engine for a breakdown or non-function, an inspection of the catalytic converters and all transferred components (such as exhaust/intake manifolds) should be performed. Any debris found should be removed. In cases of engine failure due to severe overheat, dealers should also inspect each catalytic converter for signs of melting or cracking of the ceramic “brick.” If damaged is observed, the converter should be replaced.

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