More bad castings
Owners of various GM vehicles equipped with HFV6 engines (3.0L and 3.6L) may complain about an SES light. This may be accompanied by misfire codes or possible oil or coolant leaks.
On inspection, you may find coolant or oil in one or more spark plug tubes. Determine if the oil or coolant is coming from the spark plug tube and not from fluid migrating from above. If one or more spark plug tubes is leaking, GM says to replace the cylinder head(s), spark plug(s) and coil(s).
These leaks are caused by porosity in the cylinder head casting during manufacturing. The spark plug tubes are permanently sealed into the cylinder heads and are not replaceable.
Affected vehicles include 2010-2014 GMC Acadia and Terrain, Chevy Traverse, 2012-2014 Impala and Caprice PPV, 2010-2014 Equinox, Captiva, and Camaro, 2013-2014 Cadillac XTS and ATS, 2010-2014 Buick Enclave and LaCrosse, and 2010-2014 Cadillac CTS and SRX.