Manufacturer communication — 2006 GMC YUKON DENALI XL

• Applies to 2019 and prior GM passenger cars and trucks with close-coupled catalytic converters.

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

Possible causes

• When an engine breaks down (such as a broken intake/exhaust valve or piston), debris may be deposited in the converter through the engine exhaust ports.

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  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.

• After a severe overheat, the ceramic brick inside the converter may be damaged, and ceramic debris may be drawn into the engine through the cylinder head exhaust ports.

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  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.

Steps to confirm (in the document’s order)

• When replacing an engine for a breakdown, inspect the catalytic converters and all transferred components (such as exhaust/intake manifolds) and remove any debris found.

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  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.

Repair

• After an engine failure from severe overheat, also inspect each catalytic converter for melting or cracking of the ceramic brick; if damage is observed, replace the converter.

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  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 damage is observed, the converter should be replaced.

Caution

• A replacement engine installed in either case may fail from the debris entering the combustion chambers when it is started.

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  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.