Look for Frozen PCV
This bulletin applies to 2002-2014 Chevy Avalanche, 2009-2012 Colorado, 2002-2018 Express, 2002-2013 Silverado, 2002-2018 Silverado HD, 2002-2014 Suburban, 2002-2014 Tahoe and 2003-2009 Trailblazer vehicles. Some customers may complain about an oil leak shortly after a cold start in extremely low ambient temperatures (below 10 F), or excessive short trip drive cycles.
If an oil leak from the rear main seal is noted, this is the result of a frozen PCV system and excessive crankcase pressure.
If this condition is found, clean the area of the oil leak, clean and dry the PCV hoses and replace the oil fill cap with P/N 12589430 (vented oil fill cap) to prevent a reoccurrence.