P0301, P0302, P0303, P0304, P0305, P0306
WARNING: This page is about a different car, the 2009 Pontiac Torrent and 2009 Chevrolet Equinox. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects a crankshaft rotation speed variation indicating a single cylinder misfire rate sufficient to cause emissions levels to exceed mandated standards.