CADILLAC, CHEVROLET, GMC · 2015-05-01
This Preliminary Information communication provides information to the technician on the steps to diagnose and repair vehicles that may have a buffeting vibration and/or drone type noise, exhaust tone change, and/or body pressure booming. The concern may be most noticeable while the engine is operating in 4-cylinder Active Fuel Management mode in the 1,100-1,400 RPM range. If the noise is excessive it may excite the roof sheet metal and compound the issue, if this concern is found refer to the latest version of PIT5318. If the concern is qualified to be present during V4 mode operation, but is deemed to be normal by comparing to a like vehicle, then no further repairs should be made, as this is a normal characteristic. If the concern is qualified to be present during V4 mode operation,…