The 2020 Chevrolet Silverado's 3.0L Duramax diesel relies on Diesel Exhaust Fluid (DEF) for emissions compliance. When the system detects issues, warnings and eventual power reduction ensure the truck returns for service.
How the DEF System Works
DEF is sprayed into the exhaust where it converts NOx emissions into harmless nitrogen and water through selective catalytic reduction (SCR). The system monitors DEF quality, level, and injector function continuously.
Common DEF System Problems
DEF Quality Sensor Issues
The quality sensor can fail or become contaminated, incorrectly reporting poor DEF quality. Sensor failures are common causes of unwarranted warnings.
Crystallization in DEF System
DEF can crystallize in lines, injector, or tank if the vehicle sits unused or in extreme temperatures. Crystal buildup blocks flow and triggers system faults.
DEF Injector Problems
The DEF injector can clog or fail electronically. Without proper DEF injection, the SCR catalyst can't reduce NOx, triggering warnings and eventual derates.
Contaminated DEF
DEF contaminated with water, diesel, or other fluids causes system errors. Even small contamination percentages trigger quality warnings.
Derate Schedule
When DEF issues persist, the ECU progressively limits power: first a warning, then reduced torque, and eventually a 5 MPH limit until the system is repaired.