Why does my GMC Sierra diesel keep throwing a check engine light for the DEF system, and what is the proper troubleshooting procedure to fix it without a fancy OBD2 scanner?
Download run
Fan-out diagram
The searches the AI actually ran for this prompt.
SEED QUERY
Why does my GMC Sierra diesel keep throwing a check engine light for the DEF system, and what is the proper troubleshooting procedure to fix it without a fancy OBD2 scanner?
1 real search · 1 real-search pass
GMC Sierra Duramax diesel DEF system warning troubleshooting owner manual reductant system service emissions message codesGoogle ↗
OBSERVED
Badge and edge weight = share of passes that produced the query. Hover a query for its intent and routing format.
Query classes
Google's semantic query class for every sub-query: what kind of answer each search is after, simulated vs real.
Classifying 1 queries…
Searches and sources
ChatGPT1 real searches · gpt-6
GMC Sierra Duramax diesel DEF system warning troubleshooting owner manual reductant system service emissions message codes Google ↗
- Bulletin No.: · static.nhtsa.gov
- 22-NA-150 Service Bulletin/Repair Instructions · oemdtc.com
- 21-NA-006 GMC Auxiliary Emission Control System TSB · tsbsearch.com
- 2025 Chevrolet and GMC Duramax Diesel 3.0L Owner Manual Supplement · contentdelivery.ext.gm.com
- 2021 Chevrolet and GMC Duramax Diesel 3.0L Owner Manual Supplement · contentdelivery.ext.gm.com