Leaky valve cover sets DTCs
Some customers may complain of a SES light with no engine performance concerns. Upon inspection, DTCs P0171 and/or P0174 may be found. This may be the result of un-metered air entering the PCV system by way of a valve cover gasket or oil filler neck/tube leak.
If SI diagnosis does not isolate the cause of the concern, inspect the valve covers for an obvious oil leak and/or loose oil fill neck/tube and repair as necessary.
This includes 2009 Buick Lacrosse and Allure, Cadillac Escalade, Chevrolet Impala SS, Corvette, Avalanche, Express, Silverado, Suburban, Tahoe and Trail Blazer, GMC Envoy, Savana, Sierra and Yukon, Hummer H2 and H3, Pontiac G8 and Saab 97x (any with 4.8, 5.3, 6.0 or 6.2L engines).