This TSB applies to 2007-2011 Cadillac Escalade/Escalade ESV/Escalade EXT, 2007-2011 Chevy Avalanche/Express/Silverado 1500/Suburban and Tahoe, and 2007-2011 GMC Savana/Sierra 1500/Sierra Denali/Yukon/Yukon XL/Yukon Denali and Yukon Denali XL, all equipped with the Gen 4 V8 engine.
Some customers may comment on a service-engine-soon light being on and/or a rough running engine. Technicians may find DTC P0300 set. Upon further investigation, technicians may find cylinder #1 and #7 spark plugs oil fouled and/or the porcelain may be cracked or broken on the combustion chamber side.
This occurs on the left side of the engine due to PCV pullover that adds additional oil to the cylinders that can foul out or damage the spark plugs.
Install a new left valve cover with the revised baffle to prevent PCV pullover.
Valve cover (2007-2008)….12570427
Valve cover (2009-2001)….12642655
Valve cover gasket………...12612045