Conditions for Clearing the DTC

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

DTC P279C is a Type C DTC.
When attempting to set ECM internal DTCs, run the engine for at least 1 minute, and then shut the engine off for 30 seconds. Following this procedure will allow for a complete ECM shutdown. Program the ECM with the latest software version and retest the DTC to see if the DTC resets.