Diagnostic Aids

WARNING: This page is about a different car, the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, and 2018 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.

Misalignment, debris or a poor connection at the transmission output speed sensor or the transfer case vehicle speed sensor can cause this DTC to set.
Verify that the following scan tool data can be obtained and is functioning properly while operating the vehicle within the Conditions for Running the DTC. Data that is questionable may indicate a concern.
- Transmission OSS scan too parameter in the Transmission Control Module scan tool data list
- Transfer Case OSS scan too parameter in the Engine Control Module scan tool data list
Internal transmission mechanical faults may cause this DTCs to set
The Actions Taken for P279A may set DTC P16F3.
DTC P279A, P279B or P279C may set before P0502, P0503, P0721, P0722, P0723, P077C, P077D, P2160 or P2161.
When attempting to set ECM DTCs, run the engine for at least 1 min, and then shut the engine off for 2 min. 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.