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Check engine light on, rough engine

Fix for rough engine and check engine light

GM service bulletin #12-06-01-001 for Service Engine Soon Light On and Rough Running Engine

GM has issued a service bulletin #12-06-01-001 to address a check engine light on (service engine soon light on), a P0300 trouble code and a rough running engine on the vehicles listed below. GM has determined that he rough running engine is caused by cracked or oil fouled spark plugs, usually on cylinders #1 and #7.

Cracked spark plug
Oil fouled spark plug

Vehicles affected

2007-2011 Chevrolet Avalanche, Express, Silverado 1500, Suburban, Tahoe

2007-2011 GMC Savana, Sierra 1500, Sierra Denali, Yukon, Yukon XL, Yukon Denali, Yukon Denali XL All Equipped with Gen4 V8 Engines

What causes cracked spark plugs?

GM has determined that the left side of the engine encounters too much oil from the PCV system. GM refers to this as PCV “pullover.” While ventilating the engine crankcase, the airflow pulls too much oil vapor into the combustion chambers on the left side of the engine which causes oil fouling, cracked porcelain, misfires and a P0300 trouble code.

Fix for P0300 and cracked spark plugs

GM has issued a revised valve cover with an internal baffle that prevents PCV pullover. Install the new valve cover and replace the spark plugs. Then clear the trouble code and you should be good.