- 2021 Single-source
2500 HD only, not available on the 3500 HD; GM Authority 2021 Sierra HD page lists it as added for 2021; the 2025 2500 HD guide change log (p.161) names QG3 in a deleted trailering note; no body-builder manual pass yet
QG3 Single-source
Documented applications
This page aggregates every documented appearance of QG3 in the GMC reference. Confidence and citations are shown per application — the same code can be better documented in one year than another.