Conditions for Clearing the DTC

WARNING: This page is about a different car, the 2008 GMC Yukon XL, 2008 GMC Yukon, 2008 Chevrolet Tahoe, 2008 Chevrolet Suburban, and 2008 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.