Technical Service Bulletin PIP4568P — 2008 GMC YUKON

This Preliminary Information communication provides information to the technician that some vehicles may have a Service Engine Soon lamp, engine misfire on cylinder 1, 4, 6, or 7 and/or tick noise. Technician will follow service information diagnosis first. If service information diagnosis does not isolate the cause of this concern perform a cylinder deactivation active fuel management system compression test in service information. If the running compression of the misfiring cylinder stays below 25 Pounds per Square Inch regardless of the active fuel management solenoid being commanded on or off, an active fuel management lifter is mechanically collapsed/stuck or unlocking as soon as the engine is started. Replace all active fuel management lifters, and all plastic lifter guides. Also perform the cylinder deactivation active fuel management Valve Lifter Oil Manifold Diagnosis and Testing in Service Information. If it isolates a concern with the Valve Lifter Oil Manifold, replace it and reevaluate the concern. The active fuel management lifters can also be monitored for proper operation by carefully inspecting the cylinder 1, 4, 6, and 7 rockers and valves while cranking or briefly and safely running the engine with the valve covers removed. If the valve or valves of an active fuel management cylinder stop moving while doing this test, the active fuel management lifter is causing the concern. For 2008-2009 Full Size Truck/SUV or a 2007-2009 Chevrolet Tahoe with the Police Package reprogram the Engine Control Module. On the 2008-2009 Pontiac G8, 2010-2011 Camaro, and 2007-2010 Full Size Trucks with active fuel management, also determine if the active fuel management pressure relief valve shield that is listed in the latest version of 10-06-01-008 has ever been installed. On passenger cars with the LS4 engine, determine if the updated oil pan gasket that is listed in the latest version of 11-06-01-007 has been installed.